A Guide to the End of the World

A Guide to

the End

of the World

E V E R Y T H I N G Y O U N E V E R W A N T E D

T O K N O W

Bill McGuire

OXFORD

UNIVERSITY PRESS

OXFORD

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For Jetsam, Driftwood, and the late, lamented Flotsam

Foreword-where will it all end?

Que sera,

Whatever will be will be

T h e future's not ours to see

[(Jay Livingston and Ray Evans)]

T h e big problem with predicting the end of the world is that, if proved right, there can be n o basking in glory. This has not, however, dissuaded armies of Cassandras from predicting the demise of our planet or the human race, only to expire themselveswithout the opportunity to proclaim 'I told you so'. To somewhat adapt the words of the great Mark Twain, the death of our race has been greatly exaggerated.

T h e big question is, however, how long will this continue to be the case?

In answer, it would be perfectly reasonable to say that of course the world is going to end-in about five billion years time when our Sun finally runs out of fuel and wells to become a bloated red giant that burns the Earth to a cinder.

A fervent eschatologist, however, would undoubtedly contest this, launching into an enthusiastic account of the many alternative a n d imaginative ways in which our world a n d our race might meet its end, of which disease, warfare, natural catastrophe, and exotic physics experiments gone wrong are but a selection. Given the current state of the planet you

might be forgiven for having second thoughts following such a litany-perhaps, after all, we will face 'doom soon' as John Leslie succinctly put it in his book The End of the World, rather than 'doom deferred'. Against a background of accelerating global warming, exploding population, and reborn super-power militarism, it may indeed be more logical for us to speculate that the human race's great adventure is about to end, rather than persist far into the future and across the vastness of galactic space.

Somewhat worryingly, Cambridge cosmologist Brandon Carter has developed an argument that supports, probabilistically, this very thesis. His 'doomsday argument' goes like this. Assuming that our race grows and persists for millions or even billions of years, then those of us alive today must belong to the infinitesimally small fraction of humans living in the earliest light of our race's dawn. This, Carter postulates, is statistically unlikely in the extreme. It is much more probable that we are alive at the same time as, say, 10 per cent of the human race. This is another way of saying that humans will cease to exist long before they have any chance to spread across space in any numbers worth talking about.

John Leslie illustrates this argument along these lines.

Imagine your name is in a lottery draw, but you don't know how many other names there are. You have reason to believe, however, that there is a 50 per cent chance that the total number is a thousand and an equal probability that the total is ten. When the tickets are drawn, yours is one of the first three. Now, there can be few people who, in such circumstances, would believe that the draw contained a thousand rather than ten tickets.

If the doomsday argument is valid-and it has withstood some pretty fierce attacks from a number of intellectual heayweight--then we may have only a few centuries' respite before one Nemesis or another obliterates our race, our planet, or both. Despite nearly a quarter of a century in the

'doom a n d disaster' business, however, I can't help being at least a little optimistic. Wiping out 6 billion or more people at a stroke will not be easy, a n d many of the so-called 'end of the world' scenarios are actually n o such thing, but would simply result-at worst-in a severe fall in human numbers and/or the reduction of our global, technological civilization to something far simpler a n d more parochial-at least for a time. Personally, therefore, I am open-minded about what Stephen Baxter calls in his recent novel Manifold Time the

'Carter Catastrophe'. There is n o question that the human race or its descendants must eventually succumb to oblivion, but that time may yet be avery long way off indeed.

This might be a good point to look more carefully at just what we understand by 'the end of the world', a n d how I will be treating the concept in this book. To my thinking, it may be interpreted in four different ways: (i) the wholesale destruction of the planet and the race, which will certainly occur if all the human eggs remain confined to our single terrestrial basket when our Sun 'goes nova' five billion years hence; (ii) the loss of our planet to some catastrophe or another, but the survival of at least some elements of our race on other worlds; (iii) the obliteration of the human race but

the survival of the planet, due perhaps to some virulent a n d inescapable disease; a n d (iv) the end of the world as we know

it. It is on this final scenario that I will be focusing here, a n d the main thrust of this book will address global geophysical events that have the potential to deal our race a n d our global technological society a severe, if not lethal blow. Natural catastrophes on a scale mighty enough to bring to an end our familiar world. I will not concern myself with technological threats such as those raised by advances in artificial intelli-gence and robotics, genetic engineering, nano-technology, and increasingly energetic high-energy physics experiments.

Neither will I a d d r e s c b a r r i n g global warming-attempts by some of the human race to reduce its numbers through nuclear, biological, or chemical warfare. Instead I want to introduce you to some of the very worst that nature can throw at us, either solely on its own account or with our help.

Although often benign, nature can be a terrible foe a n d mankind has fought a near-constant battle against the results of its capriciousnescsevere floods a n d storms, devastating earthquakes, a n d cataclysmic volcanic eruptions. So far, however, we have been quite fortunate, and our civilization has grown a n d developed against a backdrop of relative climatic and geological calm. T h e omens for the next century a n d beyond are, however, far from encouraging. Dramatic rises in temperature and sea level in coming decades induced by greenhouse gases-in combination with ever-growing populations-will without doubt result in a huge increase in the number a n d intensity of natural disasters. Counter-intuitively, some parts of the planet may even end up getting much colder a n d the UK, for example, could-in a century or two-be freezing in Arctic conditions as the Gulf Stream weakens. And what exactly happened to the predicted new Ice Age anyway? Has the threat gone away with the onset of anthropogenic (man-made) global warming or are the glaciers simply biding their time?

Although rapid in geological terms, climate change is a slow-onset event in comparison with the average human lifespan, a n d to some extent at least its progress can be measured and forecast. Much more unexpected and difficult to predict are those geological events large enough to devastate our entire society and which we have yet to experience in modern times. These can broadly be divided into extraterres-trial a n d terrestrial phenomena. T h e former involve the widely publicized threat to the planet arising from collisions with comets or asteroids. Even a relatively small, one-kilometre object striking the planet could be expected to wipe out around a quarter of the Earth's population.

T h e potential for the Earth itself to do us serious harm is less widely documented, but the threat of a major natural catastrophe arising from the bubbling a n d creaking crust beneath our feet is a real and serious one. Three epic events await us that have occurred many times before in our planet's prehistory, but which we have yet to experience in historic time. T h e last volcanic super-eruption plunged the planet into a bitter volcanic winter some 73,500 years ago, while little more than 100,000 years ago gigantic waves caused by a collapsing Hawaiian volcano mercilessly pounded the entire coastline of the Pacific Ocean. Barely a

thousand years before the birth of Christ, a n d again during the Dark Ages, much of eastern Europe and the Middle East was battered by an earthquake storm that levelled once great cities over an enormous area. There is n o question that such tectonic catastrophes will strike again in our future, but just what will be their effect on our global, technology-based society? How well we will cope is difficult to predict, but there can be little doubt that for most of the inhabitants of Earth, things will take a turn for the worse.

Living on the most active body in the solar system, we must always keep in our minds that we exist a n d thrive only by geological accident. As I will address in Chapter 4, recent studies on human DNA have revealed that our race came within a hair's breadth of extinction following the last super-eruption 73,500 years ago, and if we had been around 65

million years ago when a ten-kilometre asteroid struck the planet we would have vanished with the dinosaurs. We must face the fact that, as long as we are all confined to a single planet in a single solar system, the long-term survival of our race is always going to be tenuous. However powerful our technologies become, as long as we remain in Earth's cradle we will always be dangerously exposed to nature's every violent whim. Even if we reject the 'doom soon' scenario, it is likely that our progress as a race will be continually impeded or knocked back by a succession of global natural catastrophes that will crop u p at irregular intervals as long as the Earth exists and we upon it. While some of these events may bring to an end the world as we know it, barring another major asteroid or comet impact on the scale of the one which killed the dinosaurs, the race is likely to survive and, generally, to advance. At some point in the future, therefore, we will begin to move out into space-first to our sibling worlds and then to the stars. In the current inward-looking political climate it is impossible to say when a serious move into space will happen, but happen it will a n d when it does the race will breathe a collective sigh of relief. At last some of our eggs will be in a different basket. What happens next is anyone's guess. As this book will show, when it comes to geophysics, what will be, will be.

Bill McGuire

Hampton, England

August 2 0 0 1

Contents

List of Illustrations

1 A Very Short Introduction to the Earth 2 Global Warming: A Lot of Hot Air?

3 The Ice Age Cometh

4 The Enemy Within: Super-Eruptions, Giant Tsunami, and the Coming Great Quake

5 The Threat from Space: Asteroid and Comet Impacts

Epilogue

Appendix A: Threat Timescale

Appendix B: Geological Timescale

Further Reading

Index

List of Illustrations

1

Map of the Earth's plates with locations of recent natural disasters

Apocalypse, Cassell, 1999

2

The lithosphere

Apocalyse, Cassell, 1999

3 A tornado

National Oceanic and Atmospheric Administration/

Department of Commerce, Washington

4 Collapsed building, Gujarat quake 2001

Peter MacDiarmid/Rex Features

5 Aftermath of the 1998 Sissano tsunami (Papua New Guinea) Brian Cassey/AP Photo

6 Ruins of St Pierre (Martinique) after 1902 eruption Mary Evans Picture Library

7 Increasing concentrations of greenhouse gases over the last 1,000 years

8 The greenhouse effect

The Independent, 1 2 July 2001

9

Temperature rise over (a) last 1,000 years and (b) last 140 years

IPCC 3rd Assessment Report

1 0 Map of annual mean change in temperature between now and 2 100

IPCC 3rd Assessment Report

11

Flooding in Mozambique, March 2000

Clive Shirley/Panos Pictures

L I S T O F I L L U S T R A T I O N S

1 2 Damage to Miami from Hurricane Andrew, 1992

52

Sipa/Rex Features

13 World's polluters

6 1

14 Snowball Earth: artist's impression of an ice-covered planet 71

Patrick E. Smith, University of Toronto

15 Temperature changes over the past 420,000 years 75

16 Milankovich cycles

76

17 Map of extent of glaciers of last Ice Age 79

18 Ice fair on the Thames, 1739-40

Museum of London

1 9 The Atlantic Overturning Circulation 8 9

2 0

Comparisons of temperatures in this interglacial period and the last

90

2 1 Rabaul

Bill McGuire

2 2 Yellowstone

Bill McGuire

23 Satellite image of Lake Toba

24 Sunlight reduction due to Toba

Apocalypse, Cassell, 1999

25 Mount St Helens 1980 eruption: collapse of north flank 1 1 1

Corbis

26 La Palma's Cumbre Vieja volcano

116

Bill McGuire

27 Model of tsunami generated by collapse of La Palma 117

28 Collapsed building after Gujarat quake 1 2 2

Bill McGuire

29 Tokyo map

124

L I S T OF I L L U S T R A T I O N S

30 Devastation after 1923 Tokyo quake

Hulton Archive

3

Comet Shoemaker-Levy impacts on Jupiter

1

MSSSO, ANU/Science Photo Library

32 Orbits of known Earth-Crossing Asteroids. 1. Mercury 2.Venus 3. Earth 4. Mars

'Target Earth' by Duncan Steel

33 Impact crater map

34 Meteor crater

Corbis

35 Flattened trees at Tunguska

Novosti Press Agency/ Science Photo Library 36 Artist's impression of the Chicxulub impact V. L. Sharpton. Courtesy of the Lunar and Planetary Institute, Houston

37 Zones of destruction due to variously sized impacts centred on London

38 The Torino Scale

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Danger: nature at work

e are so used to seeing on our television screens the battered remains of cities pounded by earthquakes or the thousands of terrified refugees escaping from yet another volcanic blast that they n o longer hold any surprise or fear for us, insulated as we are by distance a n d a lack of true empathy. Although not entirely immune to disaster themselves, the great majority of citizens fortunate enough to live in prosperous Europe, North America, or Oceania view great natural catastrophes as ephemeral events that occur in strange lands far, far away.

Mildly interesting but only rarely impinging upon a daily existence within which a murder in a popular soap opera or a win by the local football team holds far more interest than 50,000 dead in a Venezuelan mudslide. Remarkably, such an attitude even prevails i n regions of developed countries that are also susceptible to volcanic eruptions and earthquakes. Talk to the citizens of Mammoth in California about the threat of their local volcano exploding into life, or to the inhabitants of Memphis, Tennessee, about prospects for their city being levelled by a major quake, and they are likely to shrug a n d point out that they have far more immediate things to worry about. T h e only explanation is that these people are in denial. They are quite aware that Page 3

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terrible disaster will strike at some point in the future-they just can't accept that it might happen to them or their descendants.

When it comes to natural catastrophes on a global scale such an attitude is virtually omnipresent, pervading national governments, international agencies, multinational trading blocks, a n d much of the scientific community. There is some cause for optimism, however, a n d in one area, at least, this has begun to change. T h e threat to the Earth from asteroid and comet impacts is now common knowledge and the race is on to identify all those Earth-approaching asteroids that have the potential to stop the development of our race in its tracks. Thanks to recent widely publicized television documentaries shown in the UK a n d United States, the added threats of volcanic super-eruptions a n d giant tsunamis have now also begun to reach an audience wider than the tight groups of scientists that work on these rather esoteric phenomena.

In fact, the Earth is an extraordinarily fragile place that is fraught with danger: a tiny rock hurtling through space, wracked by violent movements of its crust a n d subject to dramatic climatic changes as its geophysical and orbital circumstances vary. Barely 10,000 years after the end of the Ice Age, the planet is sweltering in some of the highest temperatures in recent Earth history. At the same time, over-population and exploitation are dramatically increasing the vulnerability of modern society to natural catastrophes such as earthquakes, floods, a n d volcanic eruptions. In this intro-ductory chapter, current threats to the planet a n d its people Page 4

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are examined as a prelude to consideration of the bigger threats to come.

T h e Earth is the most dynamic planet in our solar system, and it is this dynamism that has given us our protective magnetic field, our atmosphere, our oceans, and ultimately our lives. The very same geophysical features that make the Earth so life-giving a n d preserving also, however, make it dangerous. For example, the spectacular volcanoes that in the early history of our planet helped to generate the atmosphere a n d the oceans have in the last three centuries wiped out a quarter of a million people a n d injured countless others. At the same time, the rains that feed our rivers a n d provide us with the potable water that we need to survive have devastated huge tracts of the planet with floods that in recent years have been truly biblical in scale. In any single year since 1990

perhaps 20,000 were killed and tens of millions affected by raging floodwaters, and in 1998 major river floods in China and Bangladesh led to misery for literally hundreds of millions of their inhabitants. I could go on in the same vein, describing how lives made enjoyable by a fresh fall of snow are swiftly ended when it avalanches, or how a fresh breeze that sets sailing dinghies skimming across the wave tops can soon transform itself into a wailing banshee of terrible destruction-but I think you get the picture. Nature provides us with all our needs but we must be very wary of its rapidly changing moods.

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The Earth: a potted biography

The major global geophysical catastrophes that await us down the line are in fact just run-of-the-mill natural phenomena writ large. In order to understand them, therefore, it is essential to know a little about the Earth a n d how it functions. Here, I will sashay through the 4.6 billion years of Earth history, elucidating along the way those features that make our world so hazardous a n d our future upon it so precarious. To begin, it is sometimes worth pondering upon just how incredibly old the Earth is, if only to appreciate the notion that just because we have not experienced a particular natural catastrophe before does not mean it has never happened, n o r that it will not happen again. T h e Earth has been around just about long enough to ensure that anything nature can conjure u p it already has. To give a true impression of the great age of our planet compared to that of our race, perhaps I can fall back on an analogy I have used before. Imagine the entirety of Earth's history represented by a team of runners tackling the three a n d a half laps of the 1,500 metres. For the first lap our planet would be a barren wasteland of impacting asteroids a n d exploding volcanoes.

During the next the planet would begin to cool, allowing the oceans to develop a n d the simplest life forms to appear. T h e geological period known as the Cambrian, which marked the real explosion of diverse life forms, would not begin until well after the bell has rung a n d the athletes are hurtling down the final straight of the last lap. As they battle for the tape, dinosaurs appear and then disappear while the leaders Page 6

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are only 25 metres from the finish. Where are we? Well, our most distant ancestors only make an appearance in the last split-second of the race, just as the exhausted winner breasts the tape.

Since the first single-celled organisms made their appearance billions of years ago, within sweltering chemical soups brooded over by a noxious atmosphere, life has struggled precariously to survive a n d evolve against a background of potentially lethal geophysical phenomena. Little has changed today, except perhaps the frequency of global catastrophes, and many on the planet still face a daily threat to life, limb, and livelihood from volcano, quake, flood, a n d storm. The natural perils that have battered our race in the past, and which constitute a growing future threat, have roots that extend back over 4 billion years to the creation of the solar system a n d the formation of the Earth from a disc of debris orbiting a primordial Sun. Like our sister planets, the Earth can be viewed as a lottery jackpot winner; one of only nine chunks of space debris out of original trillions that managed to grow and endure while the rest annihilated one another in spectacular collisions or were swept up by the larger lucky few with their stronger and more influential gravity fields. This sweeping-up p r o c e s c k n o w n as accretion-involved the Earth and other planets adding to their masses through collisionswith other smaller chunks of rock, an extremely violent process that was mostly completed-fortunately for u c a l m o s t 4 billion years ago. After this time, the solar system was a much less cluttered place, with considerably less debris hurtling about a n d impacts on the Page 7

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planets less ubiquitous events. Nevertheless, major collisions between the Earth a n d asteroids and comets-respectively rocky and icy bodies that survived the enthusiastic spring cleaning during the early history of the solar system-are recognized throughout our planet's geological record. As I will discuss in Chapter 5, such collisions have been held responsible for a number of mass extinctions over the past half a billion years, including that which saw off the dinosaurs. Furthermore, the threat of asteroid and comet impacts is still very much with us, and over 300 Potentially Hazardous Asteroids (or PHAs) have already been identified that may come too close for comfort.

T h e primordial Earth would have borne considerably more resemblance to our worst vision of hell than today's stunning blue planet. T h e enormous heat generated by collisions, together with that produced by high concentrations of radioactive elements within the Earth, would have ensured that the entire surface was covered with a churning magma ocean, perhaps 400 kilometres deep. Temperatures at this time would have been comparable with some of the cooler stars, perhaps approaching 5,000 degrees Celsius. Inevitably, where molten rock met the bitter cold of space, heat was lost rapidly, allowing the outermost levels of the magma ocean to solidify to a thin crust. Although the continuously churning currents in the molten region immediately below repeatedly caused this to break into fragments and slide once again into the maelstrom, by about 2.7 billion years ago more stable a n d long-lived crust managed to develop a n d to thicken grad-ually. Convection currents continued to stir in the hot a n d Page 8

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partially molten rock below, carrying out the essential business of transferring the heat from radioactive sources in the planet's deep interior into the growing rigid outer shell from where it was radiated into space. T h e disruptive action of these currents ensured that the Earth's rigid outer layer was never a single, unbroken carapace, but instead comprised separate rocky plates that moved relative to one another on the backs of the sluggish convection currents.

As a crust was forming, major changes were also occurring deep within the Earth's interior. Here, heavier elements--

mainly iron and nickel-were slowly sinking under gravity towards the centre to form the planet's metallic core. At its heart, a ball made up largely of solid iron and nickel formed, but pressure and temperature conditions i n the outer core were such that this remained molten. Being a liquid, this also rotated i n sympathy with the Earth's rotation, in the process generating a magnetic field that protects life on the surface by blocking damaging radiation from space and provides us with a reliable means of navigation without which our pion-eering ancestors would have found exploration- and returning home again-a much trickier business.

For the last couple of billion years or so, things have quiet-ened down considerably on the planet, and its structure a n d the geophysical processes that operate both within a n d at the surface have n o t changed a great deal. Internally, the Earth has a threefold structure. A crust made u p of low-density, mainly silicate, minerals incorporated into rocks formed by volcanic action, sedimentation, a n d burial; a partly molten mantle consisting of higher-density minerals, also Page 9

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silicates, and a composite core of iron a n d nickel with some impurities. Ultimately, the hazards that constantly impinge upon our society result from our planet's need to rid itself of the heat that is constantly generated in the interior by the decay of radioactive elements. As in the Earth's early history, this is carried towards the surface by convection currents within the mantle. These currents in turn constitute the engines that drive the great, rocky plates across the surface of the planet, and underpin the concept of plate tectonics, which geophysicists use to provide a framework for how the Earth operates geologically.

T h e relative movements of the plates themselves, which comprise the crust a n d the uppermost rigid part of the mantle (together known as the lithosphere), are in turn directly related to the principal geological hazards--earthquakes a n d volcanoes, which are concentrated primarily along plate margins. Here a number of interactions are possible. Two plates may scrape jerkily past one another, accumulating strain a n d releasing it periodically through destructive earthquakes. Examples of such conservative plate margins include the quake-prone San Andreas Fault that separates western California from the rest of the United States and Turkey's North Anatolian Fault, whose latest movement triggered a major earthquake in 1999. Alternatively, two plates may collide head on. If they both carry continents built from low-density granite rock, as with the Indian Ocean and Eurasian plates, then the result of collision is the growth of a high mountain range-in this case the Himalayas-and at the same time the generation of major quakes such as thatwhich Page 10

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obliterated the Indian city of Bhuj in January 2001. O n the other hand, if a n oceanic plate made of dense basalt hits a low-density continental plate then the former will plunge underneath, pushing back into the hot, convecting mantle.

As one plate thrusts itself beneath the other ( a process known as subduction) so large earthquakes are generated. Subduction is going on all around the Pacific Rim, ensuring high levels of seismic activity in Alaska, Japan, Taiwan, the Philippines, Chile, a n d elsewhere in the circum-Pacific region. This type of destructive plate margin-so called because one of the two colliding plates is destroyed-also hosts large numbers of active volcanoes. Although the mechanics of magma formation in such regions is sometimes complex, it is ultimately a result of the subduction process a n d owes much to the partial melting of the subducting plate as it is pushed down into ever hotter levels in the mantle. Fresh magma formed in this way rises as a result of its low density relative to the surrounding rocks, a n d blasts its way through the surface at volcanoes that are typically explosive and particularly hazardous. Strings of literally hundreds of active and dormant volcanoes circle the Pacific, making up the legendary Ring of Fire, while others sit above subduction zones in the Caribbean and Indonesia. Virtually all large, lethal eruptions occur in these areas, a n d recent volcanic disasters have occurred at Pinatubo (Philippines) in 1991, Rabaul (Papua New Guinea) in 1994, a n d Montserrat (Lesser Antilles, Caribbean) from 1995 until the time of writing.

To compensate for the consumption of some plate material, new rock must be created to take its place. This Page 11

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happens at so-called constructive plate margins, along which fresh magma rises from the mantle, solidifies, and pushes the plates on either side apart. This occurs beneath the oceans along a 40,000-kilometre long network of linear topographic highs known as the Mid-Ocean Ridge system, where newly created lithosphere exactly balances that which is lost back into the mantle at destructive margins. A major part of the Mid-Ocean Ridge system runs down the middle of the Atlantic Ocean, bisecting Iceland, a n d separating the Eurasian a n d African plates in the east from the North a n d South American plates in the west. Here too there are both volcanoes a n d earthquakes, but the former tend to involve relatively mild eruptions a n d the latter are small. Driven by the mantle convection currents beneath, the plateswaltz endlessly across the surface of the Earth, at about the same rate as fingernails grow, constantly modifying the appearance of our planet a n d ensuring that, given time, everywhere gets its fair share of earthquakes and volcanic eruptions.

Hazardous Earth

While earthquakes a n d volcanic eruptions are linked to how our planet functions geologically, other geophysical hazards are more dependent upon processes that operate in the Earth's atmosphere. Rather than the heat from the interior, our planet's weather machine is driven by energy from the Sun. O u r nearest star is the ultimate instigator-aided by the Earth's rotation and the constant exchange of energy a n d Page 14

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water with the oceans--of the tropical cyclones and floods that exact an enormous toll on life a n d property, particularly in developing countries. Still other lethal natural phenomena have a composite origin a n d are less easy to pigeonhole.

T h e giant sea waves known as tsunamis (or sometimes incorrectly as 'tidal waves'), for example, can be formed i n a number of different ways; most commonly by submarine earthquakes, but also by landslides into the ocean a n d by eruptions of coastal and island volcanoes. Similarly, many landslides result from a collusion between geology a n d meteorology, with torrential rainfall destabilizing already weak slopes. Although there remains an enormous amount to learn about natural hazards, their causes a n d characteristics, our current level of knowledge is truly encyclopedic-and if so desired you can indeed consultweighty and authoritative tomes focused entirely on specific hazards. Here, as a taster, my intention is to gallop you through the principal features of the major natural hazards at a pace which I hope is n o t too great, before placing their current and future impact on our society in some perspective.

At any single point and at any one time the Earth and its enclosing atmospheric envelope give the impression of being mundanely stable a n d benign. This is, however, an entirely misleading notion, with something like 1,400 earthquakes rocking the planet every day and a volcano erupting every week. Each year, the tropics are battered by up to 40 hurricanes, typhoons, and cyclones, while floods and landslides occur everywhere in numbers too great to keep track of.

In terms of the number of people affected-at least 100

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million people a year-floods undoubtedly constitute the greatest of all natural hazards, a situation that is likely to continue given afuture of rising sea levels and more extreme precipitation. River floods are respecters of neither wealth nor status, and both developed a n d developing countries have been severely afflicted in recent years, across every continent. Wherever rain is unusually torrential or persistent, it will not be long before river catchments fail to contain surface run-off a n d start to expand across their flood plains a n d beyond. In fact, the intensity of rainfall can be quite astonish-ing, with, in 1970, nearly 4 centimetres of rain falling i n just 6 0 seconds on the French Caribbean island of Guadeloupe- a world record. O n another French island, Reunion, in the Indian Ocean, a passing cyclone dropped close to 4 metres of rain during a single 24-hour period in March 1952. AS flood plains all over the world become more crowded, the loss of life and damage to property caused by swollen rivers has increased dramatically. In the spring of 1993, the Mississippi and Missouri rivers burst their banks, inundating nine Midwest states, destroying 50,000 homes a n d leaving damage totalling 20 billion US$. Massive floods occurred in many parts of the UK in autumn 2 0 0 0 as rain fell with a ferocity not seen for over 300 years. River flooding continues to pose a major threat in China, a n d has been responsible for over 5

million deaths over the last 150 years. Bangladesh has it even worse, with the country often finding two-thirds of its land area under water as a result either of floodwaters pouring down the great Ganges river system or of cyclone-related storm surges pouring inland from the Bay of Bengal. Coastal Page 16

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3 A tornado. Tornadoes contain the strongest winds on Earth, sometimes in excess of 500 kilometres an hour Page 17

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flooding due to storms probably takes more lives than any other natural hazard, with an estimated 300,000 losing their lives in Bangladesh in 1970 a n d 15,000 at Orissa, northeast India, in 1999.

Partly through their effectiveness at spawning floods, but also through the enormous wind speeds achieved, storms constitute one of the most destructive of all natural hazards.

Furthermore, because they are particularly common in some of the world's most affluent regions, they are responsible for some of the most costly natural disasters of all time. Every year, the Caribbean, the Gulf and southern states of the USA, and Japan are struck by tropical storms, while the UK a n d continental Europe suffer increasingly from severe and damaging winter storms. In 1992, Hurricane Andrew virtually obliterated southern Miami in one of the costliest natural disasters in US history, resulting in losses of 32 billion US$.

This epic storm brought to bear on the city wind speeds of up to 300 kilometres per second, leaving 300,000 buildings damaged or destroyed and 150,000 homeless. Destructive windstorms are n o t only confined to the tropics, a n d hurricane-force winds also accompany low-pressure weather systems at mid-latitudes. Many residents of southern England will remember the Great Storm of October 1987 that felled millions of trees with winds whose average speeds were clocked at just below hurricane force. More recently, in 1999, France suffered a similar ordeal as winter storm Lothar blasted its way across the north of the country. Across the ocean, the US Midwest braces itself every year for a savage onslaught from tornadoes: rotating maelstroms of solid wind Page 18

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that form during thunderstorms in the contact zone between cold, dry air from the north a n d warm, moist air from the tropics. No man-made structures that suffer a direct hit can withstand the average wind speeds of up to 500 kilometres an hour, and damage along a tornado track is usually total.

Although rarely as lethal as hurricanes, in just a few days in April 1974 almost 150 tornadoes claimed over 300 lives in Kentucky, Tennessee, Alabama, a n d adjacent states.

Of the so-called geological hazards--earthquakes, volcanic eruptions, and landslides-there is n o question that earthquakes are by far the most devastating. Every year about 3,000 quakes reach magnitude 6 on the well-known Richter Scale, which is large enough to cause significant damage a n d loss of life, particularly when they strike poorly constructed and ill-prepared population centres in developing countries.

As previously mentioned, most large earthquakes are confined to distinct zones that coincide with the margins of plates. In recent years, sudden movements of California's San Andreas Fault have generated large earthquakes in San Francisco (1989) and southern California (1994), the latter causing damage totalling 35 billion US$-the costliest natural disaster in US history. Just a year later, a magnitude 7.2

quake at the western margin of the Pacific plate devastated the Japanese city of Kobe, killing 6,000 and engendering economic losses totalling a staggering zoo billion US$-the most expensive natural disaster of all time. Four years after Kobe, the North Anatolian Fault slipped just to the east of Istanbul, generating a severe quake that flattened the town of Izmit a n d neighbouring settlements and took over 17,000

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ended

I

I

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lives. Large earthquakes can also occur, however, at locations remote from plate margins, a n d have been known in northern Europe and the eastern USA, which are n o t regions of high seismic risk. T h e last such intraplate quake devastated the Bhuj region of India's Gujarat state in January 2001, completely destroying 400,000 buildings a n d killing perhaps as many as 100,000 people. There is a truism uttered by earthquake engineers: it is buildings not earthquakes that kill people. Without question this is the case, a n d both damage to property and loss of life could be drastically reduced if appropriate building codes were both applied and enforced.

Earthquakes, however, also prove lethal through the triggering of landslides as a result of ground shaking, a n d by the formation of tsunamis. T h e latter are generated when a quake instantaneously jerks upwards-perhaps by just a metre or so-a large area of the seabed, causing the displaced water above to hurtle outwards as a series of waves.

When these enter shallowwater they build in height-sometimes to 2 0 metres or more-and crash into coastal zones with extreme force. In 1998, Sissano and neighbouring villages on the north coast of Papua New Guinea were wiped out and 3,000 of their inhabitants drowned or battered to death by a 17-metre-high tsunamis that struck within minutes of an offshore earthquake.

Estimates of the number of active volcanoes vary, but there are at least 1,500 and possibly over 3,000. Every year around 50 volcanoes erupt, some of which-like Kilauea on Hawaii or Stromboli in Italy-are almost constantly active. Others, however, may have been quiet for centuries or in some cases Page 22

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millennia a n d these tend to be the most destructive. T h e most violent volcanoes occur at destructive plate margins, where one plate is consuming another. Their outbursts rarely produce quiet flows of red lava a n d are more likely to blast enormous columns of ash a n d debris 20 kilometres or more into the atmosphere. Carried by the wind over huge areas, volcanic ash can be extremely disruptive, making travel difficult, damaging crops, poisoning livestock, a n d contaminat-ing water supplies. Just 3 0 centimetres or so of wet ash is sufficient to cause roofs to collapse while the fine component of dry ash can cause respiratory problems a n d illnesses such as silicosis. Close to an erupting volcano the depth of accumulated ash can total several metres, sufficient to bury single-storey structures. This was the fate of much of the town of Rabaul on the island of New Britain (Papua New Guinea), during the 1994 eruptions of its twin volcanoes Vulcan a n d Tavurvur. For years following the 1991 eruption of Pinatubo in the Philippines, thick deposits of volcanic debris provided a source for mudflows whenever a tropical cyclone passed overhead and dumped its load of rain. Almost a decade later, m u d pouring off the volcano was still clogging rivers, inundating towns a n d agricultural land, a n d damaging fisheries and coral reefs. Somewhat surprisingly, mudflows also constitute one of the biggest killers at active volcanoes. In 1985 a small eruption through the ice and snow fields of Columbia's Nevado del Ruiz volcano unleashed a torrent of mud out of all proportion to the size of the eruption, which poured down the valleys draining the volcano a n d buried the town of Armero and 23,000 of its inhabitants.

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6 Ruins of St Pierre (Martinique) after 1902 eruption: only two inhabitants of St Pierre survived the onslaught of the Mont volcano

Even scarier and more destructive than volcanic mudflows are pyroclastic flows or glowing avalanches. These hurricane-force blasts of incandescent gas, molten lava fragments, and blocks and boulders sometimes as large as houses have the power to obliterate everything in their paths. In 1902, in the worst volcanic disaster of the twentieth century, pyroclastic flows from the Mont

volcano on the Caribbean island of

Martinique annihilated the town of St Pierre as effectively as a nuclear bomb, within a few minutes leaving only two survivors out of a population of 29,000. The threat from volcanoes does not end there: chunks of rock collapsing from their flanks can trigger huge tsunamis, while noxious fumes can and have locally killed thousands and their livestock. Volcanic gases carried into the stratosphere, and from there around Page 24

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the planet, have modified the climate and led to miserable weather, crop failures, and health problems half aworld away.

O n the grandest scale, volcanic super-eruptions have the potential to affect us all, through plunging the planet into a frigid volcanic winter and devastating harvests worldwide.

Of all geological hazards, landslides are perhaps the most underestimated, probably because they are often triggered by some other hazard, such as an earthquake or deluge, a n d the resulting damage a n d loss of life is therefore subsumed within the tally of the primary event. Nevertheless, landslides can be highly destructive, both in isolation and in numbers.

In 1556, a huge earthquake struck the Chinese province of Shensi, shaking the ground so vigorously that the roofs of countless cave dwellings collapsed, incarcerating (according to Imperial records) over 800,000 people. In 1970, another quake caused the entire peak of the Nevados Huascaran mountain in the Peruvian Andes to fall on the towns below, wiping out 18,000 people in just four minutes and erasing all signs of their existence from the face of the Earth. Heavy rainfall too can be particularly effective at triggering landslides, a n d when i n 1998 Hurricane Mitch dumped over 3 0

centimetres of rain on Central America, it mobilized over a million landslides in Honduras alone, blocking roads, burying farmland, a n d destroying communities.

T h e final-and perhaps greatest-threat to life a n d limb comes not from within the Earth but from without. Although the near constant bombardment of our planet by large chunks of space debris ended billennia ago, the threat from asteroids a n d comets remains real a n d is treated increasingly Page 25

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seriously. Even as I write, the UK government has announced funding for a new research centre dedicated to the study of the impact threat a n d its consequences. Recent estimates suggest that around a thousand asteroids with diameters of 1 kilometre or more have orbits around the Sun that cross the Earth's, making collision possible at some point i n the future: 1 kilometre is the impactor diameter threshold for initiating a cosmic winter, due to dust lifted into the stratosphere blocking out solar radiation, for wiping out a quarter or so of the human population, and for causing general mayhem worldwide. T h e revival of interest in the impact threat has arisen as a result of two important scientific events during the last decade: first, the identification of a large impact crater at Chicxulub, off Mexico's Yucatan Peninsula, which has now been established as the 'smoking gun'

responsible, ultimately, for global genocide at the end of the Cretaceous period: second, the eye-opening collisions in 1994 of the fragments of Comet Shoemaker-Levy with Jupiter. Images flashed around the world of resulting impact scars larger than our own planet were disconcerting to say the least a n d begged the question in many quarters--what if that were the Earth?

Natural hazards and us

If you were not already aware of the scale of the everyday threat from nature then I hope, by now, to have engendered a healthy respect for the destructive potential Page 26

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of the hazards that many of our fellow inhabitants of planet Earth have to face almost on a daily basis. The reinsurance company Munich Re., who, for obvious reasons, have a considerable interest in this sort of thing, estimate that up to 1 5

million people were killed by natural hazards in the last millennium, and over 3.5 million in the last century alone.

At the e n d of the second millennium AD, the cost to the global economy reached unprecedented levels, a n d in 1999

storms and floods in Europe, India, and South East Asia, together with severe earthquakes i n Turkey and Taiwan a n d devastating landslides in Venezuela, contributed to a death toll of 75,000 and economic losses totalling 100 billion US$.

T h e last three decades of the twentieth century each saw a billion or so people suffer due to natural disasters. Unhap-pily, there is little sign that hazard impacts on society have diminished as a consequence of improvements in forecasting and hazard mitigation, and the outcome of the battle against nature's dark side remains far from a foregone conclusion.

While we now know far more about natural hazards, the mechanisms that drive them, and their sometimes awful consequences, any benefits accruing from this knowledge have been at least partly negated by the increased vulnerability of large sections of the Earth's population. This has arisen primarily as a result of the rapid rise in the size of the world's population, which doubled between 1960 a n d 2000. T h e bulk of this rise has occurred in poor developing countries, many of which are particularly susceptible to a whole spec-trum of natural hazards. Furthermore, the struggle for Page 27

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Lebensraum has ensured that marginal land, such as steep hillsides, flood plains, and coastal zones, has become increasingly utilized for farming a n d habitation. Such terrains are clearly high risk and can expect to succumb on a more frequent basis to, respectively, landsliding, flooding, storm surges, and tsunamis.

Another major factor in raising vulnerability in recent years has been the move towards urbanization in the most hazard-prone regions of the developing world. Within just a few years, and for the first time ever, more people will live in urban environments than in the countryside, many crammed into poorly sited a n d badly constructed megacitieswith populations in excess of 8 million people. Forty years ago New York and London topped the league table of cities, with populations, respectively, of 1 2 a n d 8.7 million. In 2015, however, cities such as Mumbai (formerly Bombay, India), Dhaka (Bangladesh), Karachi (Pakistan), and Mexico City will be firmly ensconced in the top ten (Table 1 ) : gigantic sprawling agglomerations of humanity with populations approaching or exceeding 20 million, a n d extremely vulnerable to storm, flood, and quake. A staggering 96 per cent of all deaths arising from natural hazards and environmental degradation occur in developing countries and there is currently n o prospect of this falling. Indeed, the picture looks as if it mightwell deteriorate even further. With so many people shoehorned into ramshackle and dangerously exposed cities it can only be a matter of time before we see the first of a series of true mega disasters, with death tolls exceeding one million.

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Table 1 The predicted ten most populous cities in the world 2015

City

Population

1. Tokyo

2. Mumbai

3. Lagos

4. Sao Paulo

5. Dhaka

6. Karachi

7. Mexico City

8. Shanghai

9. New York

10. Calcutta

Source: Munich Reinsurance 1999

T h e picture I have painted is certainly bleak, but the reality may be even worse. Future rises in population and vulnerability will take place against a background of dramatic climate change, the like of which the planet has not experienced for maybe 10,000 years. T h e jury remains out on the precise hazard implications of the rapid warming expected over the next hundred years, but rises in sea level that may exceed 8 0 centimetres are forecast in the most recent (2001) report of the IPCC (Intergovernmental Panel on Climate Change). This will certainly increase the incidence and impact of storm surges and tsunamis and-in places--raise the level of coastal erosion. Other Page 29

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consequences of a temperature rise that could reach 6

degrees Celsius by the end of the century may include more extreme meteorological events such as hurricanes, tornadoes, a n d floods, greater numbers of landslides in mountainous terrain, and, eventually, even more volcanic eruptions (see next chapter).

So is the world as we know it about to end and, if so, how?

A century from now will we be gasping for water in an increasingly roasting world or huddling around a few burning sticks, struggling to keep at bay the bitter cold of a cosmic winter? In the next chapter Iwill delve alittle further into the possibilities.

Facts to contemplate

During its earliest history, the Earth was covered in a magma ocean with temperatures--at 5,000 degrees Celsius-comparable with the surfaces of some of the cooler stars.

O u r planet's great tectonic plates move at about the same rate that our fingernails grow.

Around 1,400 earthquakes rock the planet every day.

There may be 3,000 or more active or potentially active volcanoes, about 50 of which erupt every year.

T h e tropics are battered every year by 40 or more hurricanes, typhoons, a n d cyclones.

I n 1556 a single earthquake in the Shensi province of China is estimated to have killed 800,000 people.

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At least 15 million deaths in the last millennium are attributed to natural hazards.

96 per cent of all deaths from natural hazards a n d environmental degradation now occur in developing countries.

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debate?

G lobal warming is about much more than hotter summers, winter floods, a n d farting cows. There is absolutely n o question that the Earth is warming up fast, a n d few climate scientists would argue with this. T h e dispute lies in whether or not the warming we are now experiencing simply reflects a natural turnabout in the recent global temperature trend or results from the polluting impact of human activities since the industrial revolution really began to take hold. What I find extraordinarily irresponsible is that this dispute continues to be presented, at least in some circles, as a battle between two similarly sized and equally convincing schools of scientific thought, when in fact this is far from the case. Forecasting climate change is extremely difficult, which explains why models for future temperature rise a n d sea-level change are constantly undergoing revision, but the evidence is now irrefutable: human activities are driving the current period of planetary warming.

Notwithstanding a few maverick scientists, oil company representatives, a n d the president of the world's greatest polluter, the overwhelming consensus amongst those who have a grasp of the facts is that without a reduction in greenhouse gas emissions things are going to get very bad indeed.

Amazingly, this prospect is still played down a n d intention-Page 35

ally hidden behind a veil of obfuscation by some, most recently by the-in my opinion-self-deluded Danish statistician, Blom Lomburg. In his recently published a n d widely savaged book, The Skeptical Environmentalist, Lomburg deni-grates global warming and its future impact, while at the same time, through highly selective references to scientific research, coming to the conclusion that all is right with the world. Just in case you have come across this work and been lulled by its friendly, do-nothing message into a false sense of security, let me bring you back to reality, if I may, with a few pertinent facts.

During the past 70 years, the Earth has been hotter than at any other time in the last millennium, and the warming has accelerated dramatically in just the past few decades. No doubt everyone has at least one older relative who is constantly harking back-through a rose-tinted haze-to a time when summers were hotter a n d the skies bluer. Meteorological records show, however, that this is simply a case of selective memory, and i n fact 1 5 of the hottest 1 6 years on record have occurred since 1980, with the late 1990s seeing the warmest years of all across the planet as a whole. T h e Earth is now warmer than it has been for over go per cent of its 4.6 billion year history, a n d by the end of the twenty-first century our planet may see higher temperatures than at any time for the last 150,000 years.

T h e rising temperature trend we are seeing now is not simply a climatic blip or hiccup, nor can it be explained entirely, as some would still have it, by variations in the output of the Sun, although this clearly does have a significant Page 36

effect on the climate. Rather, it is a consequence of two centuries of pollution, which is now enclosing the Earth in a n insulating blanket of carbon dioxide, methane, nitrous oxide, a n d other greenhouse gases. Since the late eighteenth century our race has been engaged in a gigantic planetary trial, the final outcome of which we can still only guess at.

Unfortunately for us the experiment has now entered a run-away phase, which, due to its inherent inertia, we cannot stop but only slow down. Even if we were to stabilize greenhouse gas emissions today, both temperatures a n d sea levels would continue to rise for many hundreds of years. T h e big question of our time is-do we have the resolve to do even this or will we r u n from the problem and let the devil take the hindmost? Let's head for the laboratory and see how things are progressing.

The p a t global warming experiment

We know from studies of polar ice cores that before the hiss of steam a n d grinding of metal on metal that heralded the arrival of the industrial world, the concentrations of greenhouse gases in the atmosphere had been pretty much constant since the glaciers retreated at the end of the last Ice Age. Since pre-industrial times, however, carbon dioxide levels in the atmosphere have risen by 30 per cent, alongside sharp increases in other greenhouse gases, in particular methane a n d nitrous oxide. Atmospheric concentrations of carbon dioxide levels are now higher than they have been Page 37

for at least 420,000 years a n d may not have been exceeded during the past 20 million years. T h e rate of increase in the gas has also been quite unprecedented, a n d was greater in the last hundred years than at any time in at least the previous 20,000. Being concoctions of the twentieth century, other polluting gases such as chlorofluorocarbons a n d hydrofluorocarbons were not even present in the atmosphere a couple of centuries ago. As these gases have accumulated in the Earth's atmosphere so they have, quite literally, caused it to act in the manner of a greenhouse, allowing heat from the Sun in but hindering its escape back out into space.

In fact, our atmosphere has operated in this way for billions of years, moderating temperature wings and extremes, but our pollution is now strongly enhancing this greenhouse effect, with the result that the Earth has been progressively warming up for most of the last hundred years.

Because the climate machine is so complex, however, n o single influence can be taken in isolation and many other factors affect global temperatures. Not least of these is the output of the Sun, which is also variable over time, a n d which must be taken into account before allocating a rising temperature trend purely to the accumulation of man-made greenhouse gases. The Sun follows a regular 11-year pattern of activity, known as the sunspot cycle, during which time its output varies by about 0 . 1 per cent. Solar output also changes over longer periods, ranging from hundreds to tens of thousands of years, a n d these can play a significant role in cooling or warming the planet and-in recent centuries-in modifying or masking the effect of anthropogenically Page 38

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derived gases. As I will address in more detail in Chapter 4, volcanic eruptions can also have a significant effect on the Earth's climate. Although the detailed picture is somewhat more complex, large explosive eruptions inject massive volumes of sulphur dioxide a n d other sulphur gases into the stratosphere, which have a broadly cooling effect through reducing the level of solar radiation reaching the Earth's surface. Significant, if short-lived, reductions in global temperatures followed the eruptions of both El Chichion (Mexico) in 1982 and Pinatubo (Philippines) in 1991. Sometimes volcanoes a n d the Sun combine to bring about longer-lasting episodes of climate change. For example, a combination of reduced solar output and elevated volcanic activity has been implicated in the medieval cold snap known by climate scientists as the Little Ice Age. This lasted from about 1450 AD to perhaps the end of the nineteenth century and saw frost fairs on the Thames and bitter winters in many parts of the world.

Attempting to pin down the true variation in global temperatures over the past thousand years is difficult, n o t least because recordsprior to the last couple of hundred years are far from reliable. A further complication arises from the fact thatwhile one part of the world might be heating up, another might be cooling down. O n e argument that is still used by opponents of anthropogenic warming is that the world underwent a pronounced cooling between 1946 and 1975, thereby invalidating the idea that elevated levels of greenhouse gases must automatically result in global warming.

More detailed examination of the record for this period reveals, however, that although much of the northern Page 41

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hemisphere cooled noticeably, the reverse was the case in the southern hemisphere, which warmed appreciably. In fact, although there was a small overall temperature fall at this time, this is now being attributed to a masking of the warming effect by sulphur gases emitted by volcanic eruptions a n d by heavy industries at the time unfettered by clean air laws.

Notwithstanding this blip, instrumental records show that temperatures have been following an inexorably upward path since such records began in 1861. The record also shows that the 1990s was the warmest decade since the mid-nineteenth century a n d 1998 the warmest year on record.

If our great experiment was designed specifically to heat up the planet then based upon the results to date it seems that we can pat one another on the back at a job well done and sit back a n d relax as the experiment grinds away of its own accord, racking up the heat a n d clocking up an ever increasing list of unexpected consequences. But of course, this was not the intention of the experiment at all. Indeed, it is only in recent decades that the polluting effect of human activities on the global environment has been thought of in these terms. T h e great experiment has never been anything other than a side effect of our race's constant thirst for more; more growth, more goods, more wealth. Now that it has become apparent that we have been messing, admittedly involuntarily, with the natural functioning of the Earth we have n o choice but to close the experiment down. Continu-ing political procrastinations a n d the muddying of the scientific waters by vested interest groups antagonistic to proposals to mitigate global warming has ensured that the Page 43

Kyoto Protocol is well and truly dead. Even had it been ratified and achieved its goal of a 5.2 per cent reduction (below 1990 levels) in greenhouse gas emissions by 2008-12, this would have had little impact on the rate of continued warming. For any real impact to be made on the rate of warming, reductions in emissions of the order of 6 0 per cent are needed now.

Rather like trying to turn around a supertanker, the enormous inertia that has already built u p in the system would still mean that, even if we came to our senses a n d made dramatic cuts in emissions within the next few years, both temperatures a n d sea levels would continue to rise for centuries to come. It seems inevitable, therefore, that we are going to face dramatic changes to our environment- some for the better, but most not. What is certain is that our children a n d their descendants are going to find the Earth avery different place.

Hothouse Earth

The world of 2 1 0 0 AD will not only be far warmer but will also be characterized by extremes ofweather that will ensure, at the very least, a far more uncomfortable life for billions.

Already, the wildly fluctuating weather patterns that are held by many to be a consequence of global warming, combined with increasedvulnerability in the developingworld, are leading to a dramatic rise in the numbers of meteorological disasters. In its 2 0 0 1 World Disasters Report, the International Federation of Red Cross and Red Crescent Societies reveals Page 44

that the annual numbers of disasters due to storms, floods, landslides, and droughts have climbed from around 200

before 1996 to almost 400 in the first year of the millennium.

Few think that the situation will get better a n d the chances are that things will get progressively worse.

Increasingly, those occupying low-lying coastal regions will be hit by rising sea levels and heavier rainfall that will mean that lethal floods become the norm rather than the exception. In contrast, more a n d more people will starve as annual rains fail year after year and huge regions of Africa and Asia fall within the grip of drought a n d consequent famine. It also looks as if the Earth will become awindier place, with warmer seas triggering more and bigger storms, particularly in the tropics. I will return to the manifold hazard implications of global warming later, but let's look now at the latest predictions for temperature rise over the next 100 years. After all, this is the critical element that will drive the huge changes to our environment in this century a n d beyond.

Earlier this year the Intergovernmental Panel on Climate Change, or IPCC, published its Third Assessment Report on global warming; three massive tomes totalling over 2,600

pages. The IPCC was established in 1988 by the UN

Environmental Programme a n d the World Meteorological Organization, with a remit to provide an authoritative consensus of scientific opinion on climate change using the best available expertise. The important word here is consensus.

Over 1,000 scientists were involved in either the writing of the report or the reviewing of its content, leaving little doubt of its validity except in the minds of the irrationally sceptical, Page 45

the eternally optimistic, or the downright Machiavellian. If the content of the third IPCC report could be summed up in a few words, they would probably be 'Did we say i n our 1995

report that things would be bad? Well, we were wrong. They are going to be much worse than that.'

Let'slook at what the panel says about rising temperatures.

Over the course of the last century, global temperatures rose by 0.6 degrees Celsius. By 2100, the IPCC worst case scenario predicts that temperatures will be almost 6 degrees Celsius higher than they are now, and even the average prediction would see us roasting as a consequence of a 4 degree Celsius rise. If this does n o t sound much, consider that just 4 or 5

degrees Celsius mean the difference between full Ice Age conditions a n d our current climate. The transition between the two involved huge changes in the Earth's environment, n o t only in the climate a n d weather but also in vegetation and animal life.

There is every reason to expect that as the post-glacial temperature rise doubles again we will experience equally dramatic changes. This time, however, there are two important differences. First, the Earth has to feed, clothe, a n d support 6 billion or more souls, rather than a few million, a n d secondly today's comparable temperature rise is taking place over the course of just a hundred years rather than thousands. Many of the consequences of such a dramatic rise in global temperatures are obvious, but others less so. T h e polar regions and mountainous areas with permanent snow a n d ice are already suffering, and warming will continue to exact a severe toll here. Over the last l o o years there has been a Page 46

massive retreat of mountain glaciers all over the world, while since the 1950s the Arctic ice has started to thin dramatically with the result that the North Pole was ice free last summer.

Furthermore, the extent of Arctic sea ice in spring a n d summer is 10-15 per cent smaller than it was 40 years ago, while ice on lakes and rivers at higher altitudes in the northern hemisphere now melts in spring two weeks earlier than a century ago. Northern hemisphere spring snow cover is already 10 per cent down on the 1966-86 mean a n d IPCC

predictions suggest that polar and mountainous regions of the hemisphere could be 8 degrees Celsius warmer by 2100.

In 1999, the concentration of carbon dioxide in the atmosphere was 367 parts per million ( p p m ) . Even if, at some future time, we managed to stabilize the concentration at 450 ppm, temperatures would continue to rise, albeit more slowly, beyond the year 2300.

Dramatically increasing the rate of melting of snow and ice means rising sea levels: tide gauge data indicate that global sea levels rose by between 10 a n d 20 centimetres during the twentieth century, and this rise is expected to escalate drastically i n the coming hundred years, with sea levels predicted to be 40 centimetres and perhaps over 80 centimetres higher by 2100. Most of the recent a n d predicted rise comes from the thermal expansion of the oceans as they warm up or by the addition of water from the rapidly melting mountain glaciers. Failure to cut back on greenhouse emissions, however, may lead in future to catastrophic melting of the Greenland and Antarctic ice sheets, resulting in terrible consequences for coastal areas. Worst case scenarios in the IPCC report Page 47

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forecast the near elimination of the Greenland Ice Sheet, generating a 6-metre rise in sea level by the year 3000. The great West Antarctic Ice Sheet appears at present to be more stable, but severe warming over the next few millennia could result in its permanent disintegration and loss. Should the Greenland Ice Sheet melt fully, then virtually all the world's major coastal cities will find themselves under water. Even without this, however, the effects of rising sea level in the next hundred years will be devastating for low-lying countries. For example, a 1-metre rise would see the Maldives in the Indian Ocean under water, while a combination of rising 1 1 Devastating floods, such as those which affected Mozambique in 2 0 0 0 , are likely to become more frequent as the Earth continues to warm

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sea level and sinking of the land surface are forecast to result in a 1.8-metre rise in Bangladesh in just 50 years or so. This will see the loss of a huge 16 per cent of the land surface, which supports 13 per cent of the population.

Coastal flooding will also be enhanced by storm surges, with the numbers affected predicted to rise by up to 200

million people by 2080. Because the oceans are so slow to respond to change, the problem of sea-level rise is not going to go away for a very long time. Even if we stabilized greenhouse gases in the atmosphere at current concentrations, sea level would continue to rise for a thousand years or more.

It has become fashionable to blame every weather-related natural disaster on global warming. While it is not possible to say that a specific storm or flood is due to warming, there is accumulating evidence for ever greater numbers of extreme weather events. Extreme precipitation events have increased by up to 4 per cent at high and mid-latitudes during the second half of the twentieth century, a n d more rainstorms, floods, a n d windstorms are forecast. Current climatic characteristics are likely to be enhanced, so regions that are already wet will get wetter and those that are dry will suffer from prolonged a n d sustained drought. Northern Europe and the UK will therefore face more floods, while the North African deserts begin to creep towards southern Europe, and Australia begins to bake beneath a blazing sun. T h e Atlantic's

'hurricane alley' is likely to get much busier in the next half-century, and predictions made in summer 2 0 0 1 in the journal Science point to more strong hurricanes battering the Caribbean islands a n d the south-eastern and Gulf coasts of Page 50

the USA. So far few are prepared to stick their necks out a n d say that this is definitely the result of global warming.

However, as a rise in sea surface temperatures has been proposed as the driving mechanism for these more powerful storms, it would seem to be a reasonable link to make; global warming means warmer seas, which in turn are likely to give us more a n d bigger storms. As the tropical Atlantic has warmed over the past five years so the rate of hurricane formation has doubled. At the same time, the storms are getting stronger, with a 250 per cent increase in storms with sustained wind speeds exceeding 175 kilometres an hour. With increased warming of the oceans expected to continue throughout the twenty-first century, prospects for the inhabitants of hurricane alley look far from rosy. Where wind leads, so waves often follow, and evidence is now coming to light of bigger a n d more powerful waves. Around the western and southern coasts of the UK, average wave heights-about 3 metres--have risen by over a metre compared to three decades ago, while the height of the largest waves has increased by an alarming 3 metres, to 10 metres. Although n o t yet attributed directly to global warming, the increased wave heights reflect changes in the weather patterns of the North Atlantic that in turn can be linked to the reorganization of our planet's weather system as it continues to warm.

More coastal erosion is already taking its toll along many sections of the UK's most exposed coastlines; a situation which is likely to get much worse a n d which will undoubtedly be exacerbated by rising sea levels a n d storms.

It also looks as if global warming is leading to more Page 51

1 2 Hurricane

Andrew caused severe destruction

in south Miami in 1992.

More and bigger hurri

canes could be o n the way

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frequent El

events; the second largest climatic 'signal'

after the seasons. An El

involves a weakening of the

westward-blowing trade winds and the resulting migration of warm surface waters from the west to the eastern Pacific, devastating local fisheries and seriously disrupting the world's climate. T h e World Meteorological Organization has just announced that another El

will be with us in 2002,

bringing heavy rains to the western USA and central a n d southern America and drought to parts of Africa a n d Asia.

T h e frequency of this particularly insidious phenomenon has risen from once every six years during the seventeenth century to once every 2.2 years since the 1970s a n d global warming is being held up as the culprit.

As the Earth continues to heat up, it looks as if it won't only be the seas a n d the skies that become increasingly agitated: the planet's crust will also join in. Already warmer temperatures in mountainous regions such as the Alps a n d the Pyrenees are causing the permafrost to melt at higher altitudes, threatening villages, towns, a n d ski resorts with more frequent a n d more destructive landslides. As the melting ice weakens the mountains, Switzerland is already experiencing more rockfalls, landslides, a n d mudflows, but things could get much worse. Whole mountainsides, consisting of billions of tonnes of rock, could collapse, burying entire communities under massive piles of rubble. Over the last 100-150 years the tops of mountains in western Europe have warmed by one or two degrees Celsius a n d this may be accelerating. In the mountains above the Swiss ski resort of St Moritz, for example, the temperature has risen by half a degree Celsius Page 53

in just the last 15 years. Continued warmingat this rate could destabilize mountain tops right across the planet, making life both difficult a n d dangerous for the inhabitants of high mountain terrain. A colleague of mine, Dr Simon Day, has even proposed that increasing rainfall on ocean island volcanoes may trigger gigantic landslides capable of sending huge tsunamis across the Pacific or Atlantic Oceans, but more about this in Chapter 4.

Clearly then, a major consequence of global warming will be a far more hazardous world, few of whose inhabitants will escape scot-free. Already, things are getting rapidly worse, particularly along low-lying coasts and islands. In the 1990s over 40 per cent of Solomon Islanders were either killed or impinged upon by storm a n d flood. Other low-lying southwest Pacific island states such as Tonga and Micronesia are also faring badly. Over the same period 1 in 12 people in Australia and 1 in zoo in the USA were hit by natural disasters, and in the UK 1 in 2,000. But this is just the start. In the first year of the new millennium, over zoo million people were affected by natural disasters-mostly flood, storm, a n d drought-an amazing 1 in 3 0 of the planet's population, a n d global warming has not really got going yet. Without doubt, all of us will be forced to embrace natural hazards as a normal, if unwelcome, part of our lives i n the decades to come.

Furthermore, the consequences of global warming stretch far beyond making the Earth more prone to natural catastrophes. Other dramatic andwidespread changes are on the way that will have an equally drastic impact on all our lives.

National economies will be knocked sideways a n d the fabric Page 54

of our global society will begin to come apart at the seams, as agriculture, water supplies, wildlife, and human health become increasingly embattled.

A few countrieswill be able to adapt to some extent but the speed of change is certain to be so rapid as to make this all but impossible for the most vulnerable countries in Asia, Africa, and elsewhere in the developingworld. Against a background of soaring populations, falling incomes, a n d increasing pollution, there is n o question that the impact of global warmingwill be terrible. O n e of the greatest problemswill be a desperate shortage of water. Even today, 1.7 billion people

-

a third of the world's population-live in countries where supplies of potable water are inadequate, and this figure will top 5 billion in just 25 years, triggeringwater conflicts across much of Asia a n d Africa. Alongside this, crop yields are forecast to fall in tropical, subtropical, a n d many mid-latitude regions, leading to the expansion of deserts, food shortages, and famine. The struggle for food and water will lead to economic migration on a gigantic scale, dwarfing anything seen today, bringing instability and conflict to many parts of the world.

In Europe and Asia trees come into leaf in spring a week earlier than just 2 0 years ago a n d autumn arrives 10 days later than it did. While this may seem beneficial, it will also encourage new pests to move into temperate zones from which they have previously been absent. Termites have already established a base in the southern UK where, in places, temperatures are now high enough for malarial mos-quitoes to survive and breed. In the tropics there will be an Page 55

enormous increase in the number of people at risk from insect-borne diseases, especially malaria and dengue fever, while the paucity of drinkable water will ensure that cholera continues to make huge inroads into the numbers of young, old, and infirm. In urban areas, a combination of roasting summers and increased pollution will also begin to take their toll on health, particularly-once again-in poor communities where air-conditioning is out of the question. With land temperatures across all continents due to rise by up to 8

degrees Celsius by the end of the century, temperate a n d tropical forests, which currently help to absorb greenhouse gases, will start to die back, taking with them thousands of animal species unable to adapt to the new conditions. And not just the forests: grasslands, wetlands, coral reefs a n d atolls, mangrove swamps, a n d sensitive polar and alpine ecosystems will all struggle to survive a n d adapt, a n d many will fail to do so. Even our leisure activities will be affected. Not only will southern Europe become too dry for cereal crops, but it will also be too hot-in the summer months at least-for sun seekers. Prospects for the winter sports industry also look bleak, with most mountain glaciers likely to have vanished by the end of the century, a n d snowfall much reduced.

From a biodiversity point of view-as well as a tourist industry one-probably the worst recent forecast is that all the great reefs will be dead a n d gone within 50 years; some of the greatest natural wonders of the world obliterated by warmer seas just so that some of us can continue to live, or strive for, lives of conspicuous consumption.

Everything I have talked about so far is either already Page 56

happening or has been predicted by powerful computer-driven climate models that are constantly being upgraded in attempts to forecast better what global warming holds in store for us. We must always be prepared, however, to expect the unexpected; drastic consequences that so far have been regarded as possible but not likely, or others that have simply not been thought of. In the next chapter I will address one of these issues in more detail: the possibility of an island of cold in northwest Europe set amidst an overheated world. Here, though, I want to raise another frightening possibility-that large sea-level changes due to global warming might trigger more volcanic eruptions, earthquakes, and giant landslides.

Sounds crazy? Evidence from the past suggests that it might well be possible. When sealevels were rising rapidly following the end of the last Ice Age 10,000 years ago, the weight of the water on continental margins appears to have had a dramatic effect, causing volcanoes to erupt, active faults to move, a n d huge landslides to collapse from continental shelf regions.

T h e average rate of sea-level rise during post-glacial times was

-at around 7 millimetres a year-just about comparable with the rise we would see should the Greenland Ice Sheet eventually succumb to global warming.

T h e problem is that we don't know how big or how fast a rise is needed to see these effects happening again, although, interestingly, the Pavlov volcano in Alaska is induced to erupt in winter when low-pressure weather systems passing over raise sea level by just a few tens of centimetres. Perhaps then, we face not just a warm but a fiery future. There are other worries too. T h e accumulation of gases from the Page 57

decomposition of organic detritus leads to the formation of what are called gas hydrates in marine sediments. These are methane solids that look rather like water ice, whose physical state is very sensitive to changes in temperature. A warming of just one degree Celsius may cause rapid dissociation of the solid into a gaseous state, exerting increased pressure on the enclosing sediments and potentially leading to the destabilization a n d collapse of a huge sediment mass. This mechanism has been put forward for triggering the Storegga Slides--

a series of gigantic submarine landslides off the coast of southern Norway-as the Earth continued to warm up 7,000

years ago. The collapses sent huge tsunamis pouring across northeast Scotland, leaving sandy deposits within the thick layers of boggy peat. If global warming really gets going a n d continues unhindered for the next few centuries then it looks as if things may start to get very exciting indeed.

The good, the bad, and the downright mad

No one on the planet is going to escape the effects of global warming, a n d for billions the resulting environmental deterioration is going to make life considerably more difficult. It is too late now to put the clock back, but we can at least attempt to alleviate the worst impacts of warming. T h e question is, will we ever b e able to achieve a worthwhile international consensus that allows us to do this with any degree of effectiveness? The Kyoto Protocol gave us some hope in 1997, with its goal of a 5.2 per cent reduction of Page 58

greenhouse gas emissions (below 1990 levels) by 2008-12, but following the failure of the USA to ratify the agreement we are back to square one. I n fact, we are even worse off than this. Without US ratification, emissions from all the industrial countries put together could rise by about 1 2 per cent by 2008-12, which is even higher than the 'business as usual'

predictions. In terms of greenhouse gas emissions, things are getting steadily worse not better. It is difficult to see how this situation can improve until the United S t a t e c t h e world's greatest polluter, emitting a quarter of all greenhouse g a s e c together with its almost equally profligate partners in crime, Australia a n d Canada, can be persuaded to join the rest of the international community in trying to tackle the problem.

Personally, I suspect that the only persuasion that will stand any chance of working will be the persistent pounding of eastern US cities by hurricanes or perhaps a decade-long drought in Australia.

T h e more global warming continues to grab the limelight, so the more we hear from what I will call the 'techno-fix tendency'. Some of their proposals for mitigating warming are wild a n d wacky, such as placing giant reflectors in space to divert solar radiation or, even more fantastically-and heaven forbid-diverting a comet or two past the Earth, using their gravity to w i n g the planet out into a n orbit further from the Sun. Others are seriously thought-out scientific options that we may well have to utilize at some point in the future if the situation gets really out of hand. T h e latter include ways of using the oceans as a dumping ground for atmospheric carbon dioxide, either by physically discarding it in the deep Page 59

ocean via pipeline a n d tanker, or by seeding the ocean with iron to encourage the growth of marine micro-organisms that extract carbon dioxide from the atmosphere. Pilot experiments have shown that both methods can work, but to operate on a large enough scale to make any difference they would be hugely expensive a n d require a concerted international effort that is difficult to foresee unless the current position becomes untenable. Furthermore, convincing public opinion that we need to mess about with the oceans in order to repair the damage we have wrought in the atmosphere would be a considerable PR coup.

There is n o doubt that if we are to have any impact on global warmingwe will all have to change our lifestyles, moving away from a disposable society a n d towards one that promotes a n d rewards the most effective a n d efficient use of available energy and resources. Tackling global warming is inextricably linked with the widespread adoption of sustain-able development. Global warming will bring to an end the world as we have known it through dramatic changes to our environment, but if the situation is not to continue to slide it must also provide the incentive and impetus for changing the way we live. In the developed world we have n o choice but to cut fuel consumption, invest in renewable energy sources, recycle on an immensely greater scale, and produce locally as much as possible rather than flying fruit and vegetables half-way around the planet. Much as I can understand their resistance, governments of developing countries must not follow the wasteful route to industrialization that Europe a n d North America have taken, for the simple and logical reason Page 60

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that if they don't, they-and their people-will be the ones who suffer most. In particular, the developing world has to embrace renewable energy sources and recycling now, a n d the world's economic powers have a duty to support them on this path. Despite the gloom after the collapse of the Kyoto Protocol, there is an alternative plan to reduce greenhouse gas emissions on the table that mightjust start things moving on the long road to stabilization and even reduction. Called Contraction & Convergence, or simply C&C, the new way forward was thought up by London's Global Commons Institute. This ingenious plan is based upon two principles. First, that greenhouse gas emissions must be reduced and, second, that the means by which this is accomplished must be fair to all. C&C therefore proposes reducing emissions on a per capita basis. International agreement will determine by how much emissions must contract each year, and then permits to emit will be allocated to all countries on the basis of their populations. T h e emission permits would be tradable so that countries such as the USA and Australia that could not manage within their allocations could buy extra ones from populous developing countries with a surplus. This remarkably simple scheme has not yet entered the limelight, but it does have many powerful supporters in the UN, Europe, and China, a n d even amongst developing countries and US senators. It is now inevitable that we and our descendants are going to face a long a n d hard struggle as our temperate world draws to a close and we enter the time of hothouse Earth. Perhaps, however, C&C can help to make the transition a little less desperate.

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Facts

By the e n d of this century the Earth is predicted to be hotter than at any time in the past 150,000 years.

By 2100, global temperatures are forecast to rise by up to 8 degrees Celsius over land, with sea levels up to 88

centimetres higher.

Carbon dioxide concentrations in the atmosphere may be higher than at any time in the last 20 million years.

In the year 2000, 1 in 3 0 of the world's population were affected by natural disasters.

By 2025, 5 billion people will live in countries with inadequate water supplies.

Within 50 years all the world's great reefs will have been wiped out by higher sea temperatures.

T h e winter sports industry is unlikely to survive to 2 1 0 0

in its current form.

If the Greenland Ice Sheet melts, all the world's coastal cities will b e drowned, from New York to London to Sydney.

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0

n e of the main reasons for a growing disillusion-ment with science amongst the general public is the perception that scientists are always arguing with one another a n d constantly changing their minds. It is n o use explaining that this is how science progresses, through battles between competing theses until the accumulation of evidence ensures that one triumphs a n d becomes a n accepted paradigm. People want scientists to agree, to present a united front, and to tell them what is true and what is not. They want this because it makes life that much easier and gives them that much less to worry about. If you are concerned about your career or your marriage you don't want to think about whether GM crops are good or bad, or whether you have to eat your beef on the bone or off, or whether your children's children are going to fry or freeze.

Here once again, however, the scientific consensus at least appears to have done another U-turn over the last couple of decades. As we saw in the last chapter, all but the most maverick of climatologists now accept that the Earth is warming up rapidly and that our polluting activities are the cause. As recently as the 1980s, however, the big question in climatological circles was when can we expect the next Ice Age? So what has changed? Well, actually, not much. As I will explain Page 67

shortly, the glaciers are still due to advance once again a n d we should expect our planet to be plunged into bitter cold within the next few thousand years. What has changed, however, is the recognition that anthropogenic warming and its associated climatic impact may have a role to play at a critical time of natural transition when our interglacial world is due to give itself over to ice and snow for tens of thousands of years. Problematically, however, researchers are not quite sure what this role will be, a n d although, intuitively, you might expect global warming to delay or even fend off entirely the next Ice Age, some scientists have suggested that the ongoing dramatic rise in temperatures may actually accelerate the onset of the next big freeze. Even if the latter is shown not to be the case, we still have a problem. Knowing that a new age of ice is on the way should we not be trying actively to keep our planet warm? Should we not welcome global warming with open arms? In other words, we are currently faced with a stark choice that is only rarely voiced during the great global warming debate. How do we wish our familiar, contemporary world to end-by fire or by ice?

How to freeze a planet

During the Earth's early history the surface boiled with lava oceans and explodingvolcanoes, and although temperatures fell dramatically as prevailing geological processes moder-ated, our planet has been bathed in warmth for most of its 4.6 billion year history. Occasionally, however, a fortuitous Page 68

combination of circumstances has heralded the formation of enormous ice sheets that have transformed a balmy paradise into a freezing hell. Artists' impressions a n d television documentaries have ensured that most of us are familiar with the last great Ice Age, when mammoths roamed the tundra and our pelt-covered ancestors struggled to eke out an existence from afrozen world. Only recently, however, have studies of ice-related rock formations around the world brought to light a far more ancient a n d much more terrible period of refrigeration; a time when our planet was little more than a frozen snowball hurtling through space. Long, long ago, during a geological episode that is becoming increasingly a n d appropriately referred to as the Cryogenian (after cryogen for freezing mixture), the Earth found itself at a critical threshold in its history. It had cooled substantially since its formation over three and a half billion years earlier a n d now the problem was keeping itself warm. At this time, between about 800 and 600 million years ago, the Sun was weaker and the Earth was bathed in some 6 per cent less solar radiation than it is now. Furthermore, the concentrations of greenhouse gases that are now heating up our planet-primarily carbon dioxide and methane-were not sufficiently high to hold back the bitter cold of space. Huge ice sheets rapidly formed and pushed towards the equator from both poles, encasing the Earth in a carapace of ice a kilometre thick. As the blind-ingwhite shell reflected solar radiation back into space, temperatures fell to -50 degrees Celsius a n d prospects for an eternity of ice seemed strong. But something must have happened to break the ice, as it were, otherwise I would not Page 69

be here today to tell you about it; a n d in fact it seems that these 'snowball' conditions may have developed u p to six times, succumbing each time to a return of warmer climes.

Just how the Earth managed to escape the clutches of the ice n o one is quite certain, but it looks as if volcanoes might have been the saviours. After millions or even tens of millions of years of bitter cold, the enormous volumes of carbon dioxide pumped out by erupting volcanoes seem to have generated a sufficiently large greenhouse effect to warm the atmosphere a n d melt the ice. Extraordinarily, life came through this particularly traumatic period of Earth history bruised a n d battered but raring to go, and hard on the heels of Snowball Earth's final fling came the great explosion of biodiversity that marked the start of the Cambrian period 565 million years ago. Compared to the great freezes of the Cryogenian our most recent Quaternary ice ages come across as rather small beer. Nevertheless, although they affected smaller areas of the Earth's surface, these latest bouts of cold were crucial because they coincided with the appearance a n d evolution of our distant ancestors. Furthermore, they may yet have a role to play in the future of our race.

Duringrecent Earth history the Sun's output has been significantly higher than during the Cryogenian a n d the level of carbon dioxide a n d other greenhouse gases has also been higher. Why then, at the end of the Miocene period about 10

million years ago, did glaciers once again begin to form a n d advance across parts of the northern hemisphere? And more importantly, why, around 3 million years ago, did the southward march of the ice intensify? This remains a particularly Page 70

T H E I C E A G E C O M E T H

14 Snowball Earth: artist's impression of an ice-covered planet. During the Earth's early history, ice advanced from the poles to transform the planet into a great snowball

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hot topic in the fields of Quaternary science a n d environmental change and a detailed analysis of competing theories is beyond the scope of this book. Suffice it to say that explan-ations for the twenty or so ice ages that have gripped the Earth during the last 2 million years include disruption of the planet's atmospheric circulation due to uplift of the great Himalayan mountain belt, and the drastic modification of the global system of ocean currents by the emergence of the Panama Isthmus.

Although one or both of these spectacular geophysical events may have contributed to a picture of increasing cold, the ice was already on the move, a n d we need to look elsewhere for the true underlying cause. What, in other words, turns ice ages on, and-just as importantly-what turns them off! This problem has intrigued scientists for many years a n d the solution was first put forward by the Scottish geologist James Croll as long ago as 1864 and expanded upon by the Serbian scientist Milutin Milankovitch in the 1930s. T h e Croll-Milankovitch astronomical theory of the ice ages proposes that long-term variations in the geometry of the Earth's orbit and rotation are the fundamental causes of the blooming and dying of the Quaternary ice ages. In order for a n ice age to get going, the astronomical theory requires that summers at high latitudes in the northern hemisphere are sufficiently cool to allow the preservation of winter snows. As more a n d more snow a n d ice accumulates year on year, so the reflectiv-ity or albedo of the surface is increased, causing summer sun-shine to have even less impact and accelerating the growth of ice sheets a n d glaciers. But how are the northern hemisphere Page 72

summers cooled down in the first place? This is where the astronomy comes in. Cooler summers at high latitudes result from a reduction in the amount of solar radiation falling on the surface, a n d this in turn depends upon both changes in the tilt of the Earth's axis andvariations in its orbit about the Sun.

If the Earth's axis was not tilted then we would not experience the seasons. During the northern hemisphere summer, for example, the North Pole is tilted towards the Sun, allowing more direct solar radiation to reach the surface in the northern hemisphere and raising the temperatures. In contrast, during the winter, the North Pole is tilted away from the Sun and the long, balmy days of summer are replaced by the cold and dark of a northern hemisphere winter. Now the southern hemisphere receives more direct sunlight with the result that those down under bask in warmth while the north shivers beneath gloomy skies. Although the tilt of the Earth's axis averages about 23.5 degrees, it is not constant. Like a spinning top, the Earth wobbles-or precesses--

about its axis of rotation over a period of between 23,000 a n d 26,000 years. Furthermore, this wobble causes the amount of tilt to vary between 2 2 and 25 degrees over a period of 41,000 years. At times of least tilt, winters are actually milder, but more importantly, high latitudes receive less direct solar radiation and become cooler, making the survival of winter snows and the growth of ice sheets easier. O n top of this there is another so-called astronomical forczngmechanism that contributes to the onset of ice age conditions. Like all planetary bodies, the Earth follows an elliptical rather than a circular Page 73

path around the Sun, whose shape varies according to cycles of between 100,000 and 400,000 years. At the moment the Earth's closest approach to the Sun occurs in January, when the North Pole is pointing away from the Sun, resulting in slightly colder northern hemisphere winters. Just 11,000

years ago, however, this closest approach- or perihelion occurred in July, giving a small temperature boost to northern hemisphere summers.

Before this gets too complicatedlet me try and draw things together. Regular and predictable cycles-known as Milankovitch Cycles--are recognized in the behaviour of the Earth's tilt a n d its orbit over periods of thousands to hundreds of thousands of years, a n d these cycles control the amount of solar radiation reaching the Earth's surface and therefore its temperature. At times, a number of cycles may coincide so as to depress summer temperatures at high latitudes to a degree sufficient to allow the accumulation of winter snows. O n its own this could not result in the huge ice sheets that have dominated the northern hemisphere for much of the last few million years, but as the area covered by snow a n d ice grows, so more and more sunlight is reflected back into space, accelerating the cooling process. This-in essence-is how ice ages start. Conversely, at other times, the various cycles cancel one another out, the planetwarms as a result, and the ice sheets retreat to their polar fastnesses.

Although Milankovitch and later researchers who have addressed the issue have been able to explain the mechanics of the ice ages a n d their periodicity, they have been less successful in deciding why these icy episodes appeared on Page 74

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In the meantime, on the basis that there is at least a fair chance that we will have to face them again at some time in the future, let's examine what conditions were like in the depths of the last Ice Age. As temperatures started to fall around 120,000 years ago, so more a n d more of the planet's water found itself locked up in mountain glaciers, polar sea ice, a n d expanding continental ice sheets in the northern hemisphere, with the result that sea level began to fall dramatically. Ice w e p t southwards towards the equator on at least four occasions over this period, with the peak of ice cover being reached a mere 15,000-20,000

years ago.

At this time sea level was a good 120 metres or so below what it is now-about the height of a 40-storey building-exposing new land bridges between continents a n d permitting the migration of both animals a n d our distant ancestors.

O n e of these land bridges developed across the Bering Straits, allowing people from Asia to cross into North America, from which, eventually, they colonized the New World.

Just 600 generations ago, then, the north of our planet was in the steely grip of full glaciation with a third of all land covered by ice a n d 5 per cent of the world's oceans frozen.

Compared to today, the environment at the height of the last Ice Age was desperately hostile, with mean temperatures 4

degrees Celsius lower than today but far lower at high latitudes in the north. In the UK, temperatures were reduced by between 15 and 2 0 degrees Celsius, transforming the country into a frozen wasteland with great sheets of ice reaching as far south as the River Thames a n d beyond. Some of the most Page 77

inhospitable conditions were, however, to be found in North America, where temperatures over huge areas were 25

degrees Celsius lower than today a n d ice fields kilometres thick ensured that life was largely impossible. Remarkably, however, just as it seemed as if the world might be returning to the 'snowball' state of the Cryogenian, a surprising change took place. T h e planet started to warm rapidly, melting the great ice sheets at a rate far quicker than it took them to form. Meltwater poured into gigantic lakes at the margins of the ice fields, which, i n turn, emptied into the oceans, raising sea level a n d inundating land exposed just a few thousand years earlier. By 12,000 years ago, sea level was rising far more rapidly than even the most pessimistic forecasts for the next century, possibly by as much as 10 metres or so in a couple of centuries, and all the time the climate was becoming warmer and warmer-well, almost all the time that is.

The journey from the depths of ice age to the current balmy interglacial was a rather bumpy one, and on more than one occasion the ice made a concerted attempt to reclaim centre stage. Around 11,000 years ago, for example, the rapid retreat of the ice was stopped in its tracks as a new blast of cold initiated a thousand-year-long freeze, known as the Younger Dryas to distinguish it from an earlier and less severe cold phase called the Older Dryas. No one is certain what caused this sudden cold snap but one suggestion is that the culprit was a huge discharge of fresh water from long-gone Lake Agassiz, one of the gigantic glacial meltwater lakes that had accumulated in North America. The catastrophic empty-ing of this lake into the St Lawrence, and thence into the Page 78

T H E I C E A G E C O M E T H

17 Ice covered huge areas of the Northern Hemisphere land masses during the last Ice Age

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North Atlantic, may have disrupted currents carrying warmer waters into polar regions, allowing the climate at higher latitudes to cool and ice to form once again. T h e Younger Dryas and similar post-Ice Age cold snaps teach us a number of important lessons that we would do well to remember as our own world undergoes dramatic climate change. First, the witch from warm to cold a n d vice versa can occur extraordinarily rapidly-within decades-and second, the disruption of ocean currents can have serious a n d far-reaching consequences for climate change. Some worrying implications of the latter I will address in more detail later in this chapter.

Charles Dickens, White Christmases, and the Little Ice Age

It seems likely that almost everyone who has read this far is familiar with the Ice Age, but what about the Little Ice Age?

This is the term used by climatologists to describe a cold period that lasted from at least 1450--and possibly 1200--

until between 1850 a n d the start of the twentieth century.

Over this period, glaciers advanced rapidly, engulfing alpine villages, a n d sea ice in the North Atlantic severely disrupted the fishing industries of Iceland and Scandinavia. Eskimos are alleged to have paddled as far south as Scotland, while the once thriving Viking community in Greenlandwas cut off and never heard from again.

Annual mean temperatures in England during the late seventeenth century were almost one degree Celsius lower than for the period 1920--60, leading to bitter, icy winters in Page 80

which 'frost fair' carnivals were held regularly on a frozen River Thames and snowfall was common. T h e snowy winters described in many of the works of Charles Dickens may well be a reflection of this colder climatic phase, a n d they have certainly done much to nurture our constant expectation of-and wish for-an old-fashioned 'white Christmas'.

Just what was the cause of the Little Ice Age remains a matter of intense debate. Clearly, however, as most of the cold snap occurred prior to the industrial revolution there can be n o question of human activities having played a role.

Despite this, it is vital that we understand the Little Ice Age in the context of global warming, if for n o other reason than if we don't appreciate the natural variations of our planet's recent climate it is well nigh impossible to unravel the effects arising from human activities. In fact, the Little Ice Age was n o t the only significant departure from the climatic norm-if there is such a thing-in historical times. Immediately prior to this cold snap, Europe, at least, was revelling in the so-called Medieval Warm Period. This time of climate amelior-ation, between about 1000 a n d 1300 AD, saw grapes grown in England 300 miles further north than at present, while the Norse settlers of Greenland were able to graze their livestock in areas that are now buried beneath ice. T h e emergence of the world from the Little Ice Age towards the end of the last century, coincident with the acceleration of industrialization on a global scale, has contributed in n o small way to current arguments on the causes of contemporary warming.

As I noted in the last chapter, the overwhelming scientific consensus views global warming as being anthropogenic in Page 81

nature, but some still hold out for an entirely natural cause; seeing the current warming in terms of the planet coming out of the Little Ice Age and entering another warm period analogous to the Medieval Warm Period. Although the available evidence irresistibly supports a human cause rather than a purely natural warming, there can be n o question that the impact of human activities is superimposed upon a natural variability that in the recent past has resulted in significant climate change. But what is the cause? O n e of the most likely culprits is the Sun, whose output continues to vary on time scales ranging from 100 to 10,000 years. For example, the two coldest phases within the Little Ice Age corresponded closely with two periods of apparently reduced solar activity; the Sporer Minimum between 1400 and 1510 AD and the Maunder Minimum from 1645 to 1715. During these periods, virtually n o sunspots were visible a n d auroras were almost non-existent, suggesting a fall in the rate of bombardment of the Earth by solar radiation. While solar physicists estimate that the Sun during the Maunder Minimum may have been just a quarter of one per cent dimmer than it is today, this mighthave been sufficient to cause the observed cooling. Other factors may also have made a contribution, however, a n d a recent theory has given elevated levels of explosive volcanic activity at the time-including the great 1815 eruption of Indonesia's Tambora volcano-at least a supporting role in the Little Ice Age cooling. As I will discuss further in the next chapter, large volcanic explosions are particularly effective at injecting substantial volumes of sulphur dioxide and other sulphur gases into the stratosphere- that Page 82

T H E I C E A G E C O M E T H

18 During the Little Ice Age winters were often cold enough for ice fairs on the River Thames

part of the atmosphere above 1o kilometres or so. Here they mix with atmospheric water vapour to form a fine mist of sulphuric acid that cuts out a proportion of incoming solar radiation and leads to a cooling of the troposphere (the lower atmosphere) and surface.

A very British ice age

The more we learn about past climate change, the more it becomes apparent that dramatic variations can occur with extraordinary rapidity. The return-possibly within a few decades-from increasingly clement conditions to the bitter cold of the Younger Dryas, 1 1,000 years ago, demonstrates Page 83

this, as does the similarly rapid transition from the Medieval Warm Period to the Little Ice Age. Equally disturbing is the tendency for the climate to flip suddenly from one extreme to another when it is under particular stress, as it is at the moment from anthropogenic warming. This once again raises the question I posed at the beginning of this chapter-is there any way that current global warming can actually bring a return to colder conditions? While this would seem to be counter-intuitive, there is increasing evidence that this may well happen-at least as far as the UK and northwest Europe are concerned. T h e only reason why it is possible for tropical palms to thrive in western Ireland a n d southwest England is because the Gulf Stream carries northwardswarm water from the Caribbean. As a result, the UK a n d Ireland are substantially warmer than comparable latitudes in eastern Canada, which have to put u p with sub-Arctic conditions.

But what would happen if the supply of warm water from the south were shut down? It is highly likely that the British climate-and perhaps that of much of northwest Europe-would become bitterly cold, and some have suggested it could even rival that of Svalbard (formerly Spitsbergen), the ice-shrouded islands off east Greenland where the polar bear is king.

O n e of the ways of weakening or shutting down the Gulf Stream is by short-circuiting it through releasing huge quantities of cold fresh water into the North Atlantic, and this is just what is predicted by a number of different climate models developed to look at the impact of global warming in this century a n d beyond. If greenhouse gas emissions double Page 84

over the next 70 years then the warming currents could well weaken by u p to 30 per cent. Even worse, under a 'business as usual' scenario, greenhouse gas emissions will quadruple by the end of the century, leading- according to one model-to a complete shutdown of the supply of warm water to the northeast Atlantic by the middle of the next century.

In little more than half a century, then, the seas around the UK could be significantly cooler, altering prevailing weather patterns and bringing colder conditions to the region. While the rest of the world roasts, the UK and northwest Europe could conceivably start to slide into a freeze very much more bitter than the Little Ice Age. And this might be just the start.

T h e knock-on effects of changes to the ocean circulation in the North Atlantic may spread, overwhelming the current warming and bringing a return of the ice across the northern hemisphere. In conclusion, then, let's take a look at prospects for the return of the Ice Age and the role mankind may already be playing in its reappearance.

Out of the frying pan into the fridge

In terms of the Milankovitch Cycles, our planet is already primed for the end of the current interglacial a n d a return to full Ice Age conditions. Some believe that all that is needed is a trigger; a sudden shock to the system that will knock the climate out of equilibrium and set it wobbling before it collapses into an altogether less friendly state. It is questionable whether global warming can provide a shock of the Page 85

appropriate magnitude, but new research is leading to increasing concern that the legacy of warming today may be freezing tomorrow. Once again, the key seems to lie in the ocean circulation system of the North Atlantic, which appears to be closely bound up with past witches from warm to cold episodes a n d vice versa. T h e Gulf Stream that most people are familiar with is actually only one part of a system of currents known by a variety of names, of which the Atlantic Overturning Circulation is probably the most revealing. As the warm waters of the Gulf Stream head northwards they cool and consequently become more dense. As a result, by the time they have reached the Arctic Ocean they have sunk to form a cold, deep-ocean current that heads south once more to join the wider system of ocean currents known as the Global Conveyor.

It now looks as if operation of the Atlantic Overturning Circulation is seriously disrupted whenever cold conditions grip the northern hemisphere. During the Younger Dryas, for example, the circulation appears to have been severely reduced, lowering north European temperatures by as much as 10 degrees Celsius. Recent evidence on ocean temperatures a n d salinities, gleaned from studies of the shells of tiny marine organisms known as foraminifera, also points to a much weaker Gulf Stream at the height of the last Ice Age some 20,000 years ago. Then, it seems, the Gulf Stream had only two-thirds of its current strength, suggesting that the entire circulation system was comparably weakened. T h e question is, did this weakening have a role to play in the triggering of the last Ice Age, or was it merely a consequence?

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No one really knows, but there is a general feeling that a weakening of the circulation results in much colder conditions in the northern hemisphere and that such aweakening appears to be associated with large influxes of cold water into the North Atlantic. Due to melting of Arctic sea ice and the Greenland Ice Cap, this is just what is predicted to happen in the next few centuries.

During the Younger Dryas, 11,000 years ago, the release of huge quantities of water from glacial lakes resulted only in a short-lived cold snap of a thousand years or so. Then, however, the Earth was at a point in the pattern of Milankovitch Cycles when temperatures were on the way up. Now, we are poised at the transition between the present interglacial a n d the next Ice Age, a n d without the polluting effects of human activities temperatures could be expected to be on the way down. It is not unreasonable to at least consider, then, that the influx of cold, fresh water into the Arctic Ocean may trigger n o t just a brief period of cold in northwest Europe, but a new Ice Age affecting the entire northern hemisphere.

And we may not have too long to wait. In the 1990s, US

climate modellers Ronald Stouffer and Alex Hall ran a comprehensive computer model of the Earth's climate system for almost a decade to find out what it had in store for us in the next few millennia. What they discovered was seriously disturbing. T h e model predicts that, in around 3,000 years'

time, intense westerly winds over Greenland will help to push large quantities of fresh Arctic water into the North Atlantic.

Because of its low density, this bitterly cold water will remain at the surface, cooling the air above, and creating a low-Page 87

pressure weather system that will reinforce the westward gales through a positive feedback mechanism. The effect is forecast to cool the North Atlantic by up to 3 degrees Celsius and also to weaken the Atlantic Overturning Circulation, bringing colder conditions to northwest Europe. In the model, the chilly scenario only persists for 40 years or so, but the authors are concerned that if global warming promotes the melting of Greenland ice on a grand scale, this added input of cold water might amplify a brief regional cooling into a widespread a n d persistent freeze. Even more worryingly, the first signs of the coming chill may already have been detected, with recent measurements revealing that an important current running south between Scotland and the Faeroe Islands has slowed by around 20 per cent in the past 50 years. Could this be the first evidence of the breakdown of the Atlantic Overturning Circulation and the slow but steady deterioration of the climate into bitter cold?

O n e of the best means of illustrating just what a bad time this is for us to be experimenting with the global climate is by comparing the temperature profile of this interglacial with that of the last. It is rather sobering to see that the natural temperature trend is already downwards, a n d in fact this fall has been going on for several thousand years. At the moment, it looks as if the downward trend is being reversed by anthropogenic warming, and without greenhouse gas emissions the world would be around 3 degrees colder in around 8,000 years' time-well on its way to the next Ice Age. Although fending off the chill at the moment, however, the impact of global warming on the Atlantic Overturning Page 88

T H E I C E A G E C O M E T H

30"W

0" 50"N

19 Warm water from the tropics heads towards the pole to be replaced by cold Arctic waters heading south

Circulation might well ultimately accelerate the arrival of the next Ice Age.

By now I hope to have convinced you that it is at least feasible for the current global warming to trigger colder conditions, and that this may be the result of the continued and unmitigated emission of greenhouse gases. So what happens if the world comes to its senses and we cut back significantly on the amount of carbon dioxide and other gases that we pump into the atmosphere? Well, you have seen Page 89

T H E I C E A G E C O M E T H

-40,000

-30,000

-20,000

-10,000

0

10,000

20,000

Year (AD)

2 0 Comparisons of temperatures in this interglacial period and the last suggest that we are already well on the way to the next ice age the graphs-the ice will get us anyway. It is simply just a matter of whether we want to take the icy plunge on its own or spend some time baking in the sauna first. Whichever choice we make, there is no denying that life for our descendants will become increasingly hard, should the ice return. Life in Europe, North America, Russia, and central and eastern Asia will be pretty much impossible, engendering mass migrations southwards accompanied undoubtedly by bloody wars fought over living space and resources. The climate of Ice Age Earth is simply not suited to sustaining a population totalling 8-10

billion, or thereabouts, and widespread famine alongside civil strife is certain to lead to a severe culling of the human population. There is no question that our race will survive, as it did the last time that the ice left its polar fastnesses, but it is likely to be but a pale shadow of its former self.

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Facts to fret over

Between 800 a n d 600 million years ago, the Earth was a frozen snowball covered with ice a kilometre or more thick.

Just 600 human generations have passed since the end of the last Ice Age.

At the height of last Ice Age, temperatures in the UK

were 15-20 degrees Celsius lower than they are now, a n d over much of North America, more than 25 degrees Celsius lower.

Sea levels have risen by over 1 2 0 metres since the ice started to retreat around 18,000 years ago.

Unmitigated greenhouse gas emissions may lead to a shutting off of the Atlantic Overturning Circulation within a century and a half.

An Atlantic current flowing between Scotland and the Faeroe Islands has weakened by 20 per cent in the last 50 years.

Without greenhouse gas emissions, the world could be 3

degrees Celsius colder in 8,000 years.

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Hell on Earth

'magine the worst possible vision of hell. The vile stench of sulphurous gas pervading a world of darkness broken

. only by a dull red glow on a distant, invisible horizon.

Heavy, grey ash pours from above like snow, clogging the eyes, nose, a n d ears as swiftly as you can remove it. Choking and retching you ram your fingers into your mouth to try a n d gouge out the ashy, gritty slime that forces its way in with every struggling breath, but to n o avail. Suddenly a blinding flash reveals the nightmare landscape of Tolkien's Mordor-all familiar features blotted out a n d buried by ash accumulati n g a t half a metre an hour. A titanic crash of thunder heralds the return of the darkness a n d the onset of a truly biblical deluge. Within seconds the ashy drifts are transformed into rushing torrents of mud that almost sweep your feet from under you. As the falling rain a n d ash combine, you are battered by pellets of mud that begin to weigh you down under a sticky, ever-thickening carapace of Vulcan's ordure. There is n o sign that the Sun ever bathed the landscape in itswarming rays, but it is far from cold. In fact, your body is slowly roasting in the stifling heat of nature's own oven, your sweat suck-ing you dry as it drains from every pore to mix with the muddy rivulets covering every inch of your skin.

Some of the half a billion inhabitants of the danger zones Page 95

around the world's 500 or so historically active volcanoes don't need to use their imagination. They have already experienced hell. Show the above description to survivors from the 1991 eruption of Pinatubo (Philippines) or the twin eruptions of Vulcan and Tavurvur at Rabaul (Papua New Guinea) three years later, a n d they will nod their heads a n d say 'I have been there!' However awful it might sound to those of us who live far from the slopes of an erupting volcano, there is nothing unusual about the above scene. But what if it was enacted 1,500 kilometres from the eruption?

Then it really would be something very special, because it would mean that the Earth was being rent by one of nature's greatest killers-a volcanic super-eruption. These gigantic blasts dwarf even the greatest eruptions of recent times, a n d in comparison the cataclysmic detonation that blew Krakatoa (Indonesia) apart in 1883, killing around 36,000 of the inhabitants of Java a n d Sumatra, pales into insignificance.

Even the titanic blast that tore the Greek island of Thera to pieces one and a half millennia before the birth of Christ (thereby engineering the demise of the Minoan civilization and launching the enduring legend of Atlantis) would be little more than a firecracker alongside such a n Earth-shattering event.

Fortunately for us, super-eruptions are far from common, and it is estimated that throughout the last two million years of Earth history, there have been perhaps two such blasts every hundred millennia. While natural phenomena never stick rigorously to a timetable, it is nevertheless slightly disconcerting-given this frequency-that the last such Page 96

2 1 Ash from the erupting Tavurvur volcano continues to fall across the town of Rabaul in New Britain (Papua New Guinea) Page 97

cataclysm occurred a good 73,500 years ago. T h e really scary thing, however, is that, unlike 'normal' volcanic blasts, there is n o possibility of avoiding the devastating consequences of a volcanic super-eruption. Those of us tucked away in the most geologically friendly countries will still find our cosy world turned upside down by the next super-eruption, even if it occurs in a distant land on the other side of the planet. This is because of the severe impact it will have on the climate, the ash and gas ejected high into the atmosphere dramatically reducing the solar radiation reaching the surface and triggering a freezing volcanic winterworldwide.

Before examining the truly terrifying consequences of the next volcanic winter, let me take a more detailed look at the scale of volcanic super-eruptions, compared with the common-or-garden variety of volcanic blast. A number of scales have been devised in recent years to allow the sizes of volcanic events to be compared. O n e of the earliest a n d most commonly quoted is the Volcanic Explosivity Index or VEI devised by volcanologists Chris Newhall a n d Steve Self in 1982, primarily to allow estimation and comparison of the magnitudes a n d intensities of historical eruptions. Eruption magnitude refers to the mass of material erupted, while eruption intensity is a measure of the rate at which material is expelled. The index is logarithmic (like the better-known Richter Scale for earthquakes) which means that each point on the scale represents an eruption ten times larger than the one immediately below. Thus a VEI 5 is ten times larger than a 4, a VEI 6 a hundred times larger, a n d a VEI 7 a thousand times larger. At the bottom of the index, the gentle effusions Page 98

of lava that characterize most eruptions of Kilauea a n d Mauna Loa on Hawaii score a measly o, while mildly explosive eruptions that release sufficient ash to perhaps cover London or New York in a light dusting would register at 1 or 2 . To a volcanologist, however, things don't really start to get exciting until higher values are reached. VEI 3 a n d 4 eruptions are described, respectively, as 'moderate' a n d 'large'.

This translates into blasts big enough to cause local devastation, sending columns of ash up to 20 kilometres into the atmosphere a n d burying the surrounding landscape under piles of volcanic debris a metre or more deep. In 1994, the town of Rabaul in New Britain (Papua New Guinea) was destroyed by an eruption of this size, a n d a few years later-in 1997-Plymouth, the capital of the Caribbean island of Montserrat, suffered the same fate. Eruptions that score a 5

on the scale, such as the much-televised 1980 blast of Mount St Helens (Washington State, USA) typically cause mayhem on a regional scale, while VEI 6 eruptions can be regionally devastating a n d the effects long-lasting. The 1991 Pinatubo eruption in the Philippines was probably the largest eruption of the twentieth century, ejecting sufficient ash and debris to bury central London to the depth of a kilometre a n d making hundreds of thousands homeless. For years afterwards, mudflows continued to pour down the flanks of the once-again dormant volcano, clogging rivers, burying farmland, and flooding towns a n d cities. For the last VEI 7 eruption we have to go back almost two centuries to 1815-the year of the battle of Waterloo. As the armies of Wellington and Napo-leon jostled for position across Europe, on the distant Page 99

Indonesian island of Sumbawa, the long-dormant volcano Tambora ripped itself apart i n a gargantuan eruption that may have been the largest since the end of the Ice Age 10,000 years ago. Sir Stamford Raffles, the then British Lieu-tenant Governor of Java, reported a series of titanic deton-ations loud enough to be heard in Sumatra 1,600 kilometres away. When the eruption ended, after 34 days, it left 12,000

dead. In the ensuing months, however, a further 80,000

Indonesians succumbed to famine a n d disease as they struggled to find food a n d uncontaminated water across the ash-ravaged landscape.

Utterly devastating though the Tambora event n o doubt was to the people of Indonesia, its direct effects were none-theless confined to one part of South East Asia. Indirectly, however, much of the world was to suffer the consequences of this huge blast. Along with some 50 cubic kilometres of ash, the climactic explosions of the Tambora eruption also lofted around zoo million tonnes of sulphur-rich gases into the stratosphere, within which high-altitude winds swiftly spread them across the planet. T h e gases combined readily with water in the atmosphere to form 150 million tonnes of sulphuric acid aerosols-tiny particles of liquid that are very effective at blocking out solar radiation. Within months the northern hemisphere climate began to deteriorate and temperatures fell to such a degree that 1816 became known as the 'year without a summer.' Global temperatures are estimated to have fallen by around 0.7 degrees Celsius--perhaps a seventh of the drop required to plunge the planet into full ice age-causing summer frosts, snows, and torrential rains.

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T h e miserable weather conditions may have set just the right mood for Mary Shelley's vivid imagination to spawn its most famous offspring, Frankenstein, while the spectacular ash a n d gas-laden sunsets are said to have inspired some of J. M. W.

Turner's most brilliant works.

Certainly the weather conditions in Europe and North America during 1816 were awful, but could a volcanic eruption in a far-off part of the world really change the climate so much as to cause a breakdown i n society and end the world as we know it? Evidence from the past suggests that there is n o doubt that it can. Far back in the geological record- during the Ordovician period some 450 million years ago-an enormous volcanic explosion in what is now North America ejected sufficient ash and pyroclastic flows that, if it happened today, it would obliterate everything over an area of at least a million square kilometres. This is broadly the size of Egypt or four times the area of the UK. In addition the amount of gas a n d debris pumped into the atmosphere must have been phenomenal. A little nearer our time, just 2 million years ago, a mighty eruption at Yellowstone in Wyoming was violent enough to leave behind a gigantic crater (or up to 80 kilometres across, a n d pump out ash that fell across 16 states. Another huge eruption occurred at around

million years ago a n d yet another just years ago. If this last cataclysm occurred today it would leave the United States and its economy in tatters a n d the global climate in dire straits.

T h e eruption scoured the surrounding countryside with hurricane-force blasts of molten magma a n d incandescent Page 101

THE E N E M Y W I T H I N

gases-known as

a volume sufficient to

cover the entire USA to a depth of 8 centimetres. Ash fell as far afield as sites that are now occupied by the cities of El Paso (Texas) and Los Angeles (California), and Yellowstone ash from this eruption is even picked up in deep-sea geological cores from the Caribbean

Although no eruptions

have been recorded at Yellowstone for

years, the hot

springs, spectacular geysers, and bubbling mud pools provide testimony that hot magma still resides not far beneath the surface. This is further supported by the numerous earthquakes that regularly shake the region and the periodic swelling and subsiding of the land surface. No one knows 2 2 Hot springs, bubbling mudpools, and spectacular geysers testify to magma lurking not far beneath the surface of Yellowstone Park in Wyoming, USA

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when-or even if-Yellowstone will experience another devastating super-eruption. It is a little worrying, however, to note that these huge blasts seem to occur every years

or so. Perhaps then, we are due another any time now?

It would be easy to sit back and say-that's all very well, but these horrific events took place deep within the mists of time.

Surely they can't happen today? Thinking along these lines would be a very big mistake. I n 186 AD a massive eruption at New Zealand's Lake Taupo ejected pyroclastic flows that devastated a substantial portion of the North Island.

years ago-considerably older but still well within the time span of modern humanity- perhaps the greatest volcanic explosion ever tore a hole

kilometres across at Toba in

northern Sumatra. This huge caldera, which is now lake filled, is very much a tourist attraction, but there is evidence of a much more sinister legacy. T h e eruption of Toba may have come within a

breadth of making the human race

extinct. Estimates of the size of the blast vary, but there is n o question that-along with the Yellowstone qualifies as a VEI 8 super-eruption. It was thought that the total amount of debris ejected during the eruption was of the order of 3,000 cubic kilometres, sufficient to cover virtually the whole of Indiawith a layer of ash one metre thick. Recent evidence from deep-sea geological cores suggests, however, that the eruption might have lasted longer than previously thought a n d ejected considerably more debris, perhaps up to cubic kilometres. Almost unbelievably, this would be enough to bury the entire United States to a depth of two-thirds of

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Any of our ancestors living on Sumatra at the time would without question have been obliterated. For the human race as a whole to suffer the threat of extinction, though, the effects of the eruption would have to have been severe across the whole planet, a n d this they seem to have been. Along with the huge quantities of ash, the Toba blast may have poured out enough sulphur gases to create up to million tonnes of sulphuric acid aerosols in the stratosphere.

Thiswould have been sufficient to cut the amount of sunlight reaching the surface by go per cent, leading to global darkness and bitter cold. Temperatures i n tropical regions may have rapidly fallen by u p to

degrees Celsius, wiping out

the sensitive tropical vegetation, while over the planet as a whole the temperature drop is likely to have been around or 6 degrees Celsius, broadly the equivalent of plunging the planet into full ice age conditions within just a few months. Temperature records from Greenland ice cores suggest that the eruption was followed by at least six years of such volcanic winter conditions, which were in turn followed by a thousand-year cold 'snap'. Soon afterwards the planet entered the last Ice Age, a n d there is some speculation that in this respect, the cooling effect of the Toba eruption may have been the final straw, tipping an already cooling Earth from a n interglacial into a glacial phase from which it only fully emerged around

years ago.

What then of our unfortunate ancestors: could this period of volcanic darkness a n d cold really have brought them to their knees? It certainly seems possible. Studies of human DNA contained in the sub-cellular structures known as mito-Page 104

T H E E N E M Y W I T H I N

The gigantic eruption of Toba

years ago excavated a crater

kilometres long and plunged the world into the depths of volcanic winter

chondria reveal that we are all much too similar-genetically speaking-to have evolved continuously and without impediment for hundreds of thousands of years. The only way to explain this extraordinary similarity is to invoke the occurrence of periodic population bottlenecks during which time the number of human beings was, for one reason or another, slashed and the gene pool dramatically reduced in size. At the end of the bottleneck, all individuals in the rapidly expanding population carry the inherited characteristics Page 105

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petual darkness a n d cold for years. Photosynthesis would slow to almost nothing, destroying the food sources of both humans and the animals they fed upon. As the volcanic winter drew on, our ancestors simply starved to death leaving fewer a n d fewer of their number, perhaps in areas sheltered for geographical or climatological reasons from the worst of the catastrophe. It has been suggested that for millennia

or so there may have been only a few thousand individuals on the entire planet. This

about as close to extinction as a

species is likely to get and still bounce back, and-if must have placed our ancestors in as vulnerable a position as today's White Rhinos or Giant Pandas. Against all odds it seems that the dregs of our race managed to struggle through both the aftermath of Toba a n d the succeeding Ice Age, bringing our numbers up to the current 6 billion.

Could a future super-eruption wipe out the human race? It is highly unlikely that any eruption would be of sufficient size to completely obliterate today's teeming billions, but it is perfectly possible that our global technological society would not survive intact. Before the fall of the Berlin Wall, many national governments were quite prepared to plan for the terrible possibility of all-out nuclear war. With the threat now largely dissipated, however, there has been little enthusiasm for maintaining a civil defence plan to address the threat of a global geophysical catastrophe. In the absence of such forward thinking, the impact of a future super-eruption is likely to be appalling. With even developed countries such as the United States, the UK, Germany, a n d Australia having sufficient stores to feed their populations for a month or two at Page 107

most, how would they cope with perhaps another six years without the possibility of replenishment? In the world's poorer countries, where famine and starvation are never far away, the situation would be magnified a thousand times, a n d death would come

a n d terribly. From London to

Lagos the law of the jungle would quite likely prevail as individuals a n d families fought for sustenance a n d survival.

When the skies finally cleared and the Sun's initially feeble rays brought the first breath of warmth to the frozen Earth, maybe a quarter of the current population would have died through famine, disease, a n d civil strife.

Bearing in mind that over

millennia have elapsed since

the Toba cataclysm it would be n o surprise, statistically speaking, if another super-eruption struck within the next hundred years. But where? Restless calderas, which are constantly welling a n d shaking, are clear candidates, a n d both and Toba belong in this category. Large volumes of magma still reside beneath these sleeping giants that may well be released in future cataclysms. It is likely, however, that the warning signs of these giants' awakening-large earthquakes and severe welling of the surface-will continue for decades or even centuries before they finally let loose. As neither volcano is displaying such ominous behaviour at the moment we need not lose too much sleep over the imminence of a super-eruption at either Toba or Yellowstone.

Only a tiny percentage of the Earth's or so active

volcanoes are currently, however, being monitored. Furthermore, the next super-eruption may blast itself to the surface at a point where n o volcano currently exists. Perhaps even as Page 108

I write this some gigantic mass of magma that has been accumulating deep under the remote southern Andes may be priming itself to tear the crust apart-and our familiar world with it.

T h e super-eruptions I have talked about so far have all been cataclysmically explosive affairs. There is, however, another much less common species. O n e that-every few tens of millions of y e a r c e r u p t s even greater volumes of magma, but with relatively little violence. Flood basalt eruptions involve the effusion of gigantic volumes of low-viscosity lava that spread out over huge areas. These spectacular outpourings have been identified all over the world, including India, southern Africa, the northwest United States, a n d northwest Scotland, but the greatest breached the surface nearly 250 million years ago in northern Siberia. Estimates vary, but it looks as if the lavas erupted by this unprecedented event covered over 25 million square k i l o m e t r e c a n area three times that of the United States.

Several similar outpourings have occurred throughout the Earth's long history and have been correlated with mass extinctions. Before the Siberian outburst, for example, the Earth of the Permian period teemed with life. During the succeeding Triassic period, however, when the great flows had cooled and solidified, fully

per cent of all species had

vanished from the face of the planet. A similar mass extinction 6 5 million years ago, at the end of the Cretaceous period, has been linked to the huge Deccan Trap flood basalt eruption in northwestern India. As I will address in the next chapter, however, there is incontrovertible evidence that the Page 109

Earth was struck at this time by a comet or asteroid, a n d many scientists now believe that this was the primary cause of the extinction of the dinosaurs and numerous other species at the end of the Cretaceous. Nevertheless, the Deccan lavas may also have had a role to play, pumping out gigantic quantities of carbon dioxide that may have led to severe greenhouse warming a n d the demise of organisms that were unable to adapt quickly enough. As our polluting society continues to do the same, perhaps we should take this as a salutary warning of what the future might hold for us, our world, a n d life upon it.

A watery

Although by n o means the largest volcanic event of the twentieth century, the spectacular

eruption of Mount St

Helens, in Washington State (USA), was certainly the most filmed. Perhaps because it occurred in the world's most media-attuned country, the explosions as the volcano blew itself apart were almost drowned out by the whir of cameras and the scribbling of journalists' pencils. From a scientific point of view, however, the eruption was awatershed, because it drew attention to a style of eruption that had previously attracted little interest from volcanologists. Most eruptions involve the ejection of volcanic debris from a central vent, but the climactic eruption of Mount St Helens was quite different. Lava a n d debris from the previous eruption-all of years earlier-had blocked the central conduit ensuring Page 110

T H E E N E M Y W I T H I N

that the fresh magma rising into the volcano could not easily escape. Instead it forced its way into the volcano's north flank, causing it to swell like a giant carbuncle. By mid-May the carbuncle was

kilometres across and

metres high,

and very unstable. Just after 8.30 in the morning on 8 May, a moderate earthquake beneath the volcano caused it to shrug off the bulge, which within seconds broke up and The climatic eruption of Mount St. Helens (Washington State, USA) was triggered by the collapse of the north flank of the volcano Page 111

crashed down the flank of Mount St Helens as a gigantic landslide. With this huge weight removed from the underlying magma, the gases contained therein decompressed explosively, blasting northwards with sufficient force to flatten fully grown fir trees up to

kilkometres away a n d

obliterating, in all, over 600 square kilometres of forest. T h e landslide material rapidly mixed with river a n d lake water forming raging

that poured down the river valleys

draining the volcano, while pyroclastic flows tore down the flanks a n d ash fell as far afield as Montana kilometres

away.

T h e Mount St Helens blast killed 57 people and was a disaster for the region, but its scientific importance lies squarely in its elucidation of the mechanism known as volcano lateral collapse. Most of us view volcanoes as static sentinels: bastions of strength a n d rigidity that are unmoving a n d unmovable. In fact, however, they are dynamic structures that are constantly shifting and changing. Far from being strong they are often rotten to the core; little more than unstable piles of ash and lava rubble looking for an excuse to fall apart. The numerous studies that followed the Mount St Helens eruption revealed that collapse of the flanks a n d the formation of giant landslides is a normal part of the lifecycle of many volcanoes, and probably occurs somewhere on the planet around half a dozen times a century. Furthermore, they showed that the Mount St Helens landslide was tiny compared to the greatest known volcano collapses--with a volume of less than a cubic kilometre compared with over cubic kilometres for the prodigious chunks of rock Page 112

that have, in prehistoric times, sloughed off the Hawaiian Island volcanoes.

At this stage you might be asking yourself, so what? Surely a h u n k of rock-however large-falling off a volcano can't have a global impact-can it? Well it probably can, provided that the collapse occurs into the ocean. In a relatively

small landslide flowed down the side of Japan's Unzen volcano a n d into the sea. T h e water displaced formed tsunamis tens of metres high that scoured the surrounding coastline, killing over

inhabitants in the small fishing villages that lined the shore. Just over a century later, in 1888, part of the Ritter Island volcano off the island of New Britain (Papua New Guinea) fell into the sea, generating tsunamis up to metres high that crashed into settlements on neighbouring coastlines taking over 3,000 lives. Clearly, the combination of a volcanic landslide and a large mass of water is a lethal one, but-you are n o doubt thinking-how can it affect the vast majority of the Earth's population who live far from an active volcano? T h e answer lies partly in the size of the largest collapses and partly in the scale of the tsunamis they generate.

Underwater images of the

surrounding the Hawai-

ian Islands shows that they are surrounded by huge aprons of debris shed from their volcanoes over tens of millions of years. Within this great jumbled mass of volcanic cast-offs, nearly

individual giant landslides have been identified, some with volumes in excess of

cubic kilometres. T h e

last massive collapse in the Hawaiian Islands occurred just over

years ago from the flanks of the Mauna Loa volcano on the Big Island. Giant tsunamis resulting from Page 113

entry of this huge mass of rock into the Pacific Ocean have been held responsible for carrying coral-reef debris to a n altitude of over 300 metres above sea level on the neighbouring island of Lanai- three-quarters of the height of Chica-go's Sears Tower. Deposits of a similar age, which may be tsunamis-related, have also been recognized metres above

sea level a n d

kilometres away on the southern coast of New South Wales in Australia. While the nature and proven-ance of both deposits is still debated, the scale of the waves generated appears to be realistic, and computer models developed to simulate the emplacement of giant volcanic landslides into the ocean come up with similar sized tsunamis.

It seems, then, as if major collapses at ocean island volcanoes are perfectly capable of producing waves that are locally hundreds of metres high a n d remain tens of metres high even when they hit land half an ocean away. T h e next collapse in the Hawaiian Islands is likely, therefore, to generate a series of giant tsunamis that will devastate the entire Pacific Rim, including many of the world's great cities in the United States, Canada, Japan, a n d China. In deep water, tsunamis travel with velocities comparable to a Jumbo Jet, so barely

hours will elapse before the towering waves crash with the force of countless atomic bombs onto the coastlines of North America a n d eastern Asia.

Nor is the problem confined solely to the Pacific. Scientific cruises around the Canary Islands, together with detailed geological surveys on land, have revealed a picture very similar to that painted for Hawaii. Huge masses ofjumbled rock Page 114

stretching for hundreds of kilometres across the a n d

gigantic cliff-bounded collapse scars on land, testify to enormous prehistoric collapses from the islands of Tenerife a n d El Hierro. Of more immediate concern, it looks as if a new giant landslide has recently become activated on the Canary Island of La Palma, a n d is primed and ready to go. During the eruption before last, in much of the

western flank of the island's steep a n d rapidly growing volcano-the Cumbre Vieja-dropped

metres towards the

North Atlantic and then stopped. Some

US scientists

believe that this gigantic chunk of volcanic rock-with an estimated volume of a few hundred cubic kilometres, just about double the size of the

Isle of Man-is now

detached from the main body of the volcano and will eventually crash enmasseinto the sea. T h e problem at the moment is that we don't have a clue when this will happen. It will probably be soon-geologically speaking-but whether it will be next year or in

years we simply don't know. Measure-

ments undertaken during the late

using the satellite

Global Positioning System proved somewhat inconclusive but suggested that the landslide might still be creeping slowly seawards, perhaps at only a centimetre a year or even less.

Even if this is the case, however, the rock mass is unlikely to complete its journey into the North Atlantic without the trigger of a new eruption.

What is certain is that at some point in the future the west flank of the Cumbre Vieja on

will collapse, a n d the

resulting tsunamis will ravage the entire Atlantic rim. Steven Ward of the University of California at Santa Cruz a n d Simon Page 115

THE E N E M Y W I T H I N

26 The west flank of La Palma's Cumbre volcano is on the move

and will eventually collapse into the North Atlantic Day of University College London's

Greig Hazard

Research Centre created quite a stir recently when they published a scientific paper that modelled the future collapse of the Cumbre Vieja and the passage of the resulting tsunamis across the Atlantic. Within two minutes of the landslide entering the sea, Ward and Day show, an initial dome of water an almost unbelievable

metres high will have been

generated, although its height will rapidly diminish. Over the next 45 minutes a series of gigantic waves up to metres

high will pound the shores of the Canary Islands, obliterating the densely inhabited coastal strips, before crashing onto the African mainland. As the waves head further north they Page 116

Page 117

will start to break down, but Spain a n d the UK will still be battered by tsunamis u p to metres high. Meanwhile, to the west of La Palma, a great train of prodigious waves will streak towards the Americas. Barely six hours after the landslide, waves tens of metres high will inundate the north coast of Brazil, and a few hours later pour across the low-lying islands of the Caribbean and impact all down the east coast of the United States. Focusing effects in bays, estuaries, and har-bours may increase wave heights to

metres or more as

Boston, New York, Baltimore, Washington, and Miami bear the full brunt of Vulcan a n d Neptune's combined assault.

The destructive power of these skyscraper-high waves cannot be underestimated. Unlike the wind-driven waves that crash every day onto beaches around the world, a n d which have wavelengths (wave crest to wave crest) of a few tens of metres, tsunamis have wavelengths that are typically hundreds of long. This means that once a tsunami hits the coast as a towering, solid wall of water, it just keeps perhaps for ten or fifteen minutes or more-before taking the same length of time to withdraw. Under such a terrible onslaught all life a n d all but the most sturdily built structures will be obliterated.

Without considerable forward planning it is unlikely that the nine hours it will take for the waves to reach the North American coastline will permit effective, large-scale evacu-ation, a n d the death toll is certain to run into millions if not tens of millions. Furthermore, the impact on the US

economy will be close to terminal, with the insurance industry wiped out at a stroke and global economic Page 118

following swiftly on its heels. In this way, a relatively minor geophysical event at a remote Atlantic volcano will affect everyone on the planet. Like volcanic super-eruptions, these giant tsunamis constitute perfectly normal, albeit infrequent, natural phenomena. At some point in the future one will certainly wreak havoc in the Atlantic or Pacific Basins, but when? T h e frequency of collapses on the Hawaiian volcanoes has variously been estimated to be between 25,000 a n d years, but if giant landslides at all volcanic islands are considered, it may be that a major collapse event occurs every ten millennia or so. O n a geological timescale this is very frequent indeed a n d should provide us with serious cause for concern. Even more worryingly, the rate of collapse may not be constant a n d the current episode of global warming engendered by human activities may in fact bring forward the timing of the next collapse. My own research team has linked increased incidences of past volcano collapse with periods of changing sea level, while others have suggested that a warmer a n d wetter climate might result in greater numbers of large volcanic landslides. Given that sea levels are forecast to continue to rise for the foreseeable future, while studies of past climate change show that a warmer planet results in heavier rainfall on many of the world's largest volcanic island chains, perhaps we should all be thinking of moving inland and uphill, or at least of investing in a quality wet suit.

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The

waiting to die

It is extraordinarily difficult to get across to someone who has never experienced it the sheer, mind-numbing terror of being caught in a major earthquake. Even in California, where the population is constantly bombarded with information about what to do in the event of a quake, coherent, sensible thought ceases when the ground starts to tremble.

Following the Loma Prieta quake that struck northern California in

a survey by the United States Geological Survey revealed that only 13 per cent of the population of Santa Cruz sought immediate protection, while close to per cent either froze or ran outside. This is aperennial problem with earthquakes; however well educated the people, when the ground starts bucking like a bronco a n d the furniture starts to hurl itself across the room, blind instinct takes over and tells them to 'get the hell out of Unfortunately, this serves only to increase the death toll as terrified homeowners rushing screaming into the street provide easy targets for falling masonry a n d other debris crashing down from above. What they should b e doing is diving beneath the nearest piece of furniture or

sheltering beneath the lintel of a convenient doorway.

Earthquakes are immensely destructive, mainly because most cities in regions of high seismic risk are dominated by buildings that are simply not built well enough to withstand the severe ground shaking of a major quake. Modern construction methods in California follow stringent building codes that ensure they can withstand earthquakes that would Page 120

be devastating elsewhere, and this policy has borne considerable fruit by dramatically limiting death, injury, a n d damage during major quakes in the last

years. Even so, the

ridge earthquake that struck southern California in credited with losses totalling 35 billion US$, largely accruing from damage to older structures. Other earthquake-prone countries also have in place building codes designed to min-imize damage due to ground shaking, but often these codes are simply n o t enforced. T h e terrible legacy of such a lack of commitment by government a n d local authorities became all too apparent when a magnitude

quake struck the Izmit

region of Turkey in

obliterating

buildings a n d

taking over

lives. Many apartment blocks simply

caked; successive floors collapsing to form a pile of concrete slabs beneath which opportunities for survival were minimal.

More recently, in January 2001, a severe earthquake shook the Bhuj region of Gujarat state in northwestern India, flattening

homes a n d killing perhaps

people.

Many of the deaths resulted from the traditional construction methods used in the region, which involved the building of homeswith enormously thick walls made of great boulders held together loosely with mud or cement, beneath stone roofs. When the ground started to shake these buildings offered little resistance, collapsing readily to crush those inside.

During the last millennium, earthquakes were responsible for the deaths of at least 8 million people. Terrifying as this sounds, the rapid growth of megacities in regions of high seismic risk is set to ensure that this figure is surpassed, Page 121

T H E E N E M Y W I T H I N

maybe in just the next few centuries, and some seismologists are already warning of the potential, in the near future, for a single large quake to take 3 million lives. If the unfortunate target were Karachi or Mexico City then, although the catastrophe would have appalling consequences for the host countries, the global impact would be minimal and would barely impinge upon the lives of most of the world's population. On the other hand, if ground zero were to be the Japanese capital, Tokyo, then the story would be very different.

Projections to

suggest that by this time the Tokyo-Yokohama conurbation will be the greatest urban concentration on the planet, with a population a shade under 2 9

28 Buildings, not earthquakes, kill people.

poorly constructed

buildings succumbed to severe ground shaking during the 2 0 0 1

Gujarat earthquake in India

Page 122

million. T h e city is located in one of the most quake-prone parts of the planet, where the Pacific a n d Philippine plates to the east plunge beneath the giant Eurasian plate, a n d was obliterated by a massive earthquake less than 80 years ago.

While things have been ominously quiet since, it can't be long now before another huge quake devastates one of the world's great industrial powerhouses. When it does, the economic shock waves will hurtle out across the planet, bringing country after country to its knees. In order to provide a n impression of the fate awaiting the Japanese capital, let m e take you on a trip back to one of the great disasters of the twentieth century, the terrible event the Japanese call the Great

Earthquake.

September

dawned like any other day for the

inhabitants of Tokyo and Yokohama, but for many it would be their last. T h e quake struck just before noon, when the a n d beer halls were packed with hungry workers a n d as families sat down at home to their midday meal. A low, deep rumbling grew rapidly to a monstrous roar as a fault below Sagami Bay ripped itself apart a n d sent shock waves tearing northwards towards the twin cities, crashing first into hama and then-a bare

seconds later-into the heart of

the capital itself. T h e quake registered a massive 8.3 on the Richter Scale, a n d so severe was the ground shaking that it was impossible even to stand. Within seconds, thousands of buildings, many with the traditional wooden walls and tiled roofs, collapsed into heaps of rubble, bringing sudden oblivion to those inside. The great cacophony of grinding rock and falling buildings eventually gave way to the quieter Page 123

Page 124

but equally terrifying crackling of flames as fires started by thousands of overturned stoves began to devour the wood out of which many of the buildings were constructed.

Whipped up by a brisk wind, a million small fires swiftly merged to form unstoppable walls of flame that marched across the ruins. Shocked men, women, a n d children cowered before them in open spaces, but to n o avail. T h e firestorms roasted them alive. In one area of waste ground were immolated by the conflagration, so packed together that their charcoaled bodies were found still upright. T h e fires continued to consume what remained of the cities for two days and nights, before finally burning themselves out to reveal a post-apocalyptic scene of utter devastation. The true total will never be known but up to people may have lost their lives in the quake itself and the fires that followed. The cost to the Japanese economy was phenomenal- around

billion US$ at today's

and a combination of the quake a n d the Great Depression six years later led to economic collapse and severe hardship.

Some have even suggested that these circumstances, as in the German Weimar Republic, helped stoke the fires of national-ism and the rise of the military, leading to conquest, imperi-alism, and ultimately war.

In the early years of the new millennium, the twin cities of Tokyo

again await their fate, only this time it will be far, far worse, both

and the rest of the world.

Now the industrial and commercial might of the region constitutes one of the major hubs of the world market, with spokes reaching out to the far corners of the Earth, helping Page 125

Page 126

to bind together a global economic machine upon which the wealth of all nations now depends. When Tokyo falls, so will Japan, and the rest will follow-but when? Strains have now been accumulating in the rock beneath a n d around the capital for 78 years and, apart from a relatively magnitude 5.9-quake in

the region has been

ally silent. Both the government a n d the population know, however, that this can't last a n d money is being poured into constructing earthquake-proof buildings, improving education a n d emergency planning, a n d even trying to predict the precise timing of the next 'big one'. So far, however, the accurate prediction of earthquakes has proved to be out of reach, a n d prospects for a breakthrough in the near future are slim. Furthermore, a substantial proportion of the older building stock remains vulnerable, a n d an estimated one million wooden buildings continue to provide an excellent potential source of fuel for the post-quake fires. Just seven years ago,

people died in the Kobe earthquake, kilometres south of Tokyo, which can be viewed perhaps as a mini version of the catastrophe awaiting the capital. At Kobe serious fire damage contributed significantly to the overall destruction and to the huge economic losses of zoo billion US$, a n d it was clear that emergency preparedness a n d response were far from effective, and certainly well below the rest of the world's expectations, given the general perception of Japanese society as a model of efficiency. For one reason or another, the authorities were simply unable to cope with the chaotic aftermath of the event. Planswere n o t in place to ensure transport of emergency supplies a n d equipment to Page 127

where they were needed, once roads were blocked by debris and railways out of commission, and many of the city's hundreds of thousands of homeless received little or n o help for several days after the quake. It is fair to say that some at least of the problems encountered at Kobe reflect the hierarchical structure of Japanese society, which stifles independent decision making a n d action a n d hinders rapid response in emergency situations. Without significant changes it is difficult to see how any earthquake emergency plan for the Tokyo region could function effectively within the strait-jacket imposed by such a deeply ingrained a n d restrictive social etiquette.

T h e geological setting of Tokyo

is complex,

with three of the Earth's great tectonic plates converging here. T h e enormous strains associated with the relative movements of these plates are periodically relieved by sudden displacements along local faults, which in turn lead to destructive earthquakes. In fact, there are so many active faults in the vicinity that the region is at risk from major quakes occurring at four different locations, all of which are thought by seismologists to be overdue or at least imminent.

Some

kilometres south of Tokyo

close to

the city of Odawara, seismologists expect a magnitude 6 . 5 7

quake to strike at any moment. Although causing serious damage locally, a n d moderate damage in the twin cities, this isunlikely to hit the capitalwith the force of the quake.

Similarly, another so-called Tokai earthquake is imminent beneath Suruga Bay,

kilometres to the southwest. Scien-

tists forecast that this will be a huge, magnitude 8 event that Page 128

will undoubtedly batter the coastal city of Shozuoka, but will probably again be too far from the capital to have a serious impact. Far more worrying are two other expected quakes that pose a much greater threat to the Tokyo region, a n d which are awaited with much trepidation. Scientists predict that a quake as large as magnitude could strike at any

time-directly beneath the capital. This event, known locally as a chokka-gata quake, will cause severe damage in the capital,

is likely to be less badly hit. Worst of all, a repeat of the

Great Kanto Earthquake itself is only

thought to be a few decades away. This is likely to take the form of a massive magnitude 8 event resulting from the tearing open of a fault beneath Sagami Bay to the south. As was the case almost 80 years ago, the shock waves will race northwards, rolling first into Yokohama and barely half a minute later into Tokyo itself.

T h e national government still maintains that its scientists will detect in advance the warning signs that the 'big one' is on

Such faith in science is both rare a n d touching but in this case entirely misplaced. Retrospectively, it has been noted that some earthquakes have been preceded by falls in the water levels in wells and boreholes, a n d in elevated concentrations of radioactive radon gas issuing from the rock, but this is not always observed. Furthermore, such changes can occur without a following quake, making them notoriously unreliable for prediction purposes. A group of Greek scientists claim that they can detect electrical signals in the crust prior to an earthquake, but there is n o convincing evidence for this and the method is derided most

Page 129

seismologists. O n the other hand, there does appear to be something in the idea that animals, birds, and fish behave strangely before a quake, a n d the Japanese are actually undertaking serious research to find out if catfish-amongst other organisms-can help them forecast the next big one.

The problem here is that n o one knows how animals can detect a quake before it happens, although it has been suggested that strain in the rocks generates electrical charges in fur and feathers, and perhaps even scales, that trigger small electric shocks, making the animals understandably restless and irritable. But this begs the question, how do you decide whether, for example, a pig is behaving strangely?

In the absence of a n alert from a precognizant catfish, it is likely then, that the next great quake will strike the Tokyo region with n o warning whatsoever. Recently constructed buildings will fare reasonably well, but many older properties will crumble. Notwithstanding an automatic gas shut-off device that is fitted to some buildings, exploding fuel tanks, fractured gas mains, a n d oil and chemical spills will ensure n o shortage of fires to feed on

wooden buildings. As

in

huge conflagrations are expected to cause at least as much destruction as the quake itself, a n d to inflate the death toll hugely, which some suggest could easily top the of the Great

quake. While it is difficult to estimate in advance the economic losses resulting from the next big one, a modelling company that services the insurance industry has come up with the extraordinary figure of 7 trillion US$.

This would make the cost of the next Tokyo quake 35 times greater than Kobe, so far the most expensive natural disaster Page 130

ever, and 2 0 0 times more than California's Northridge

quake-the costliest natural catastrophe in US history.

T h e impact on the Japanese economy

expected to

be shattering. Japan is enormously centralized, and the Tokyo region hosts not only the national government but also the stock market and

per cent of the headquarters of the the world's-largest companies. Currently, the GDP of the region is comparable to that of the entire UK, and despite its current economic woes, it is likely that be substantially larger when the big one eventually strikes. In order to rebuild and regenerate it is highly likely that the Japanese will have to disinvest from abroad on a massive scale, dumping government bonds in Europe a n d the States, selling foreign assets, and shutting down overseas factories. It is well within the realms of possibility that as country after country finds itself fighting to cope with the swift unravelling of the global economy, a recession deeper than anything since the

would soon set in. Neither would it be any great surprise to find unemployment reaching staggering proportions a n d the political a n d social fabric of many states starting to pull apart. No one knows how long a post-Tokyo quake depression would last-it could be years or even how bad it would be. Equally importantly, how long do we have to wait until such a speculative scenario is played out for real? T h e frightening consensus amongst seismologists is 3 0

best.

Despite occasionally being depicted in the media as I would hate you to regard me purely as a harbinger of doom, a n d close the book at this point with a feeling of Page 131

hopelessness about the future. Yes, the Earth is geologically very dangerous, a n d the more geologists study our planet the more potentially serious the tectonic threat to the survival of our civilization appears to be. O n the other hand, we are learning all the time; collecting data that can be utilized to counter or at least mitigate the impact of the next eruption or gigantic tsunamis. Eventually, it probably will be possible to predict earthquakes with some accuracy and precision, and certainly within a century it is likely that nowhere on the planet will a volcanic island become unstable or a huge new batch of magma swell the surface without our satellites spotting them well in advance of catastrophe. O n an almost daily basis Earth scientists are tackling some of the greatest threats to our society and incrementally they are getting to grips with them. At the very least, the next time our planet shudders on a grand scale we will be far better prepared than our distant ancestors, who faced the might of Toba with incomprehension a n d sheer terror.

Facts

O n average there are two volcanic super-eruptions every millennia.

Following the Toba super-eruption

years ago, the

world would have been held in the grip of volcanic winter for at least six years.

I n the aftermath of Toba the human population may have been reduced

a few thousand individuals.

Page 132

In

a gigantic landslide on the western flank of the Cumbre Vieja volcano o n La Palma (Canary Islands) dropped

over night.

When the Cumbre Vieja collapses into the sea, the coastal cities of the eastern USA will be battered by tsunamis up to

metres high.

T h e next great Tokyo earthquake is expected to cause damage totalling at least trillion US$ a n d may trigger a global economic collapse.

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The astronomical

of the

' n

a discovery by the late a n d greatly lamented planetary scientist Eugene Shoemaker- along with his wife

. Carolyn and colleague David

to change for

ever our perception of the Earth as a safe and cosy haven insulated from the whizzes and bangs of a violent and capricious universe. The Shoemaker team had spotted huge

chunks of rock that had once been part of a comet torn apart by the enormous gravitational field of the planet Jupiter-a giant sphere mainly made up of hydrogen and helium gas that is large enough to contain over

Earths. Instead of

orbiting the Sun, like most comets, however, this one had been captured by Jupiter's gravity and the rocky fragments now orbited the King of Planets itself. As Jupiter already had a large retinue of moons, the addition of a few more would have been mildly interesting, if not surprising. What was extraordinary, however, was that these new 'moons' were very much ephemeral. T h e following year they would end their lives by crashing into the surface of Jupiter, providing scientists on Earth with a grandstand view of just what happens when a planet is struck by large hunks of space debris.

O n

July 1994- appropriately the

anniversary of the

launch of Apollo 11,

the first manned lunar landing

mission-the first fragment of Comet

struck

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T H E T H R E A T F R O M S P A C E

the planet, sending up a gigantic plume of gas a n d debris and blasting outwards a rapidly expanding shock wave. As fragment after fragment hammered into the planet, spectacular images were gathered by the Hubble Space Telescope in Earth orbit and by the unmanned Galileoprobe on its way to Jupiter. Two days after the initial impact, a chunk of rock kilometres across a n d rather unromantically named fragment G smashed into the planetwith the force of million

million tonnes of TNT-roughly the equivalent of eight lion Hiroshima-sized atomic bombs. T h e flash generated by the collision was so brilliant that many infra-red telescopes trained on the event were temporarily blinded. T h e glare soon faded, however, to reveal an enormous dark impact scar wider than the Earth. Inevitably, everyone who saw this awe-some image had the same thought. What would have happened if fragment G had struck the Earth instead Almost overnight our planet seemed a much more vulnerable place a n d the hold of our race upon it that much more tenuous. Suddenly both scientists and the public, and even politicians, began to take the threat from space seriously.

Two Hollywood blockbuster films fed growing interest in impact events by showing-with various degrees of scientific rigour-what we might all be in for if a comet or asteroid headed our way.

In

just two years after the Jupiter impacts, an international body known as the

Foundation was

formed, with the dedicated aims of promoting the search for potentially dangerous asteroids and comets a n d raising the general level of awareness of the impact threat. In the United Page 138

T H E T H R E A T F R O M SPACE

States, NASA and the Department of Defence began, albeit at a low level, to fund Spaceguard-related projects and the UK

government established a task force to examine the risk of asteroids and comets hitting the Earth. All of a sudden everyone wanted to know what the chances were of the Earth being 31 The spectacular impact of one of the fragments of Comet Shoemaker-Levy impacts on Jupiter in

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T H E T H R E A T F R O M S P A C E

struck at some point in the future and what effect such a collision would have on our planet and our race. T h e answer to the first question is easy: the chances are per cent. T h e

Earth has been bombarded by space debris throughout its long history, a n d although such collisions are now far less common than they were billions of years ago, our planet will be struck again. T h e vital question is-when? And as regards how bad this will be for the human race: that depends largely upon how big a chunk of rock hits us.

The cosmic sandstorm

To get a better idea of how frequently the Earth is likely to be hit, we need to find out how many rocks are hurtling around our solar system and, in particular, how many of these come close enough to the Earth to start us worrying. Although a vast amount of debris was w e p t up by the embryonic planets during the early solar system, countless dregs remain, ranging upwards in size from tiny specks a few millimetres across to gigantic rocks, such as the minor planet Ceres, over a kilometres in diameter. Like someone battling through a desert sandstorm, the Earth is constantly bombarded in the course of its journey through the solar system.

Fortunately for us, most of the billions of colliding fragments are tiny a n d flash into oblivion as soon as they come into contact with our planet's atmospheric shield. Every now a n d again, however, the Earth collides with something larger.

A fragment of debris the size of a pea burns up in the Page 140

T H E T H R E A T F R O M S P A C E

Earth's atmosphere every five minutes, while a soccer-ball sized lump will light up the sky with its death throes around once a month. Larger objects may run the gauntlet of the atmosphere and reach the surface, but this is rare and only happens a few times a year. Perhaps once or twice a century, the Earth collides with a rock in the metre size

range-an object large enough to obliterate a city if it scores a direct hit. T h e last well-documented impact of this size occurred as recently as 1908-ofwhich more later.

While the entire solar system teems with debris, from a hazard point of view we are only really interested in those fragments that threaten to end their existence through collision with our planet. T h e majority of these Earth-threatening objects are rocky asteroids that have orbits around the Sun that intersect the Earth's. T h e true numbers of these Crossing Asteroids

are impossible to determine, but

current estimates are pretty frightening.

In all, up to

million pieces of rock over

metres across

may be hurtling across our planet's path during its journey around the Sun. Up to

of these are thought to be

over

metres in diameter-big enough to obliterate London or New York given a direct hit-and maybe are

half a kilometre across, sufficient to wipe out a small country if they strike land, or generate devastating tsunamis if they impact in the ocean. Fewer in number, but enormously more destructive if they hit, are those asteroids kilometre or

more in diameter. O n e kilometre is widely recognized as the critical size threshold at or above which a collision would have devastating consequences on a global scale. Although Page 141

T H E T H R E A T F R O M S P A C E

barely equivalent in diameter to ten soccer pitches laid end to end, such is the tremendous level of kinetic energy-or energy of motion-involved in the collision that an object of this size striking land would leave a crater kilometres or so

across a n d loft sufficient pulverized debris into the atmosphere to block out the Sun's rays a n d plunge the Earth into a freezing cosmic winter for years.

A range of estimates have been published for the number of Earth-Crossing Asteroids in the kilometre a n d above size range, with the most recent suggesting there are somewhere between

a n d

Over

of these have now been

identified and their orbits projected forward in time to see if they pose a threat to the Earth in the medium term, and the search continues to find them all-a task that will take at least a couple more decades. Once this has been accomplished, and assuming that one does n o t have our name on it, we can sleep a little safer in our beds. T h e problem does not, unfortunately, end there. We still have the comets to worry about.

Comets are enormous masses of rock and ice that can be up to

kilometres or more across. In contrast to the circular orbits of the asteroids, most comets follow strongly elliptical paths that carry them from the freezing outposts of the outer solar system, or beyond, in close to the Sun a n d then out again. I n the depths of space, comets are enigmatic objects a n d not easy to spot. As they enter the inner solar system, however, they undergo a remarkable transformation as sunlight starts to evaporate gas a n d dust particles from the central nucleus to form a spectacular tail that can stretch Page 142

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3 2 Orbits of known Earth-crossing Asteroids provide a clear picture of just how crowded the space around our planet really is. The orbits of Mercury

Venus 3. Earth

Mars are also shown

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across space for

million kilometres or more. T h e stunning apparition of a comet's tail was long regarded as a portent of doom a n d disaster, a n d in a way this is not too far from the mark. Comets have typical velocities of kilometres

a second-a hundred times faster than Concorde, a n d around three times that of the Earth-Crossing Asteroids. As a result, a collision between a comet and the Earth is hugely more energetic

and

therefore

tremendously

more

destructive.

Another problem with comets is that, unlike their asteroid cousins, their orbital parameters are often poorly known a n d therefore difficult to project into the future to see if they pose any threat. Halley's Comet, undoubtedly the most famous of all, follows a n orbit around the Sun that takes only 7 6 years to complete. Consequently, it has been observed dozens of times over thousands of years and its orbit is well enough known to make it possible to calculate its path far into the future. This shows that, at least until AD,

ley's Comet will not even come close to threatening the Earth. Other comets, however, follow parabolic orbits that take them on immeasurably long journeys far beyond the limits of the solar system. Some of these may have been observed once or twice by our distant ancestors, but others may be making their first ever visit to the inner solar system.

In these circumstances, there has been n o opportunity to predict their orbits on the basis of earlier visitations, and our first view of one of these objects heading our way may provide us with just six months respite before an unavoidable a n d calamitous collision. Furthermore, because such comets have Page 144

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been confined to deep space, they are huge- perhaps kilometres or more across. This is because they have not suffered attrition from the solar wind, the hurricane of solar particles that evaporates parts of a comet to produce the characteristic tail, as it forges its way through the inner solar svstem.

When

collide

It has been something of a struggle over the last few centuries for exponents of the theory to convince both scientists a n d the public that the millions of craters that pockmark the face of the Moon are the result not of volcanic explosions but of collisions with objects from space. As long ago as the early nineteenth century, the German natural philosopher Baron von Paula Gruithuisen's declaration that the lunar craters were a consequence of 'a cosmic bombardment in past ages' was treated with contempt by 'serious' scientists.

(No doubt his further claims to have uncovered evidence for the existence of humans and animals o n the surface of the Moon had a little to do with this.) At the other end of the nineteenth century, the US geologist Grove Karl Gilbert tried to simulate in the laboratory the formation of the lunar craters by firing objects into powder or mud. Gilbert was perplexed, however, by the observation that only objects fired vertically produced circular craters like those that cover the lunar surface. In light of this, W. M. Smart proclaimed, in that the craters of the Moon could not be caused by Page 145

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impacts because 'there is no a

reason why meteors should

always fall vertically'. It was only after observing the effects of the billions of tonnes of bombs dropped i n the War that it began to dawn on geologists that given a violent enough explosion, a circular crater would always be whatever the angle of the trajectory. In other words, the tremendous explosion generated when a n object hit the Moon virtually always resulted in a circular crater. Remarkably, it took another quarter of a century for the impact origin of lunar craters to gain widespread acceptance, a n d even today one or two maverick scientists still support a volcanic origin in the face of overpowering evidence to the contrary. Getting any new paradigm accepted in science is a battle, a n d geology is n o exception. Just as the proponents of the revolutionary theory of plate tectonics had initially to fight hard against reactionary forces, so those scientists who claimed that the Earth, as well as the Moon, had also taken a battering found the going difficult.

As long ago as

Tilghman proposed that

Arizona's famous Barringer Crater (also now known as Meteor Crater) was the result of 'the impact of a meteor of enormous and hitherto unprecedented size'. This suggestion failed to convince, however, because a quarter of a century of excavation by Tilghman a n d his engineer colleague D. M.

Barringer failed to find the

itself. We now know

that this had been essentially vaporized by the enormous heat generated by the collision, but at the time the absence of a 'smoking gun' simply lent credence to those who suggested a n alternative mechanism of formation.

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Until well after the end of the Second World War, many Earth scientists suffered an extraordinary failure of the imagination, accepting an impact origin for the lunar craters but grabbing at any straw in order not to support an impact origin for crater structures on the surface of our own planet. Given that, due to the Earth's much greater size a n d stronger gravity field, it must have been struck perhaps 3 0

times more frequently than its nearest neighbour, this denial is even more extraordinary. Perhaps not entirely surprising, however, when we consider that the enormously dynamic nature of our planet is far from suited to the preservation of impact craters, particularly those of any great age. Because of plate tectonics, and in particular the process of subduction, through which the basaltic oceanic plates are continuously being consumed within the Earth's hot interior, some two-thirds of the Earth's surface is only a few hundred million years old. Bearing in mind that the most intense phase of bombardment occurred during the first few billion years of our planet's history, then evidence for this can now only be found in the ancient hearts of the granite continents that are immune to the subduction process. Because they have succumbed to erosion and weather-ing, perhaps for aeons, these craters are notoriously difficult to spot. Also, the oldest rocks, which are likely to support the most craters, are in remote areas such as Siberia, northern Canada, a n d Australia, a n d some craters are so big that their true form can only be seen from space. Today, satellites have helped in the identification of over 165 impact craters all over the world, and the idea that the Earth is Page 147

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susceptible to bombardment from space is now as accepted as plate tectonics.

Controversy has certainly not gone away, however, a n d argument continues amongst the scientific community, particularly about the frequency a n d regularity of impacts probably of most interest to the layman-about the effects of the next large impact on our civilization. The question of frequency is far from straightforward a n d serious disagreement exists between schools of thought that, on the one hand, support a constant flux of impactors and, on the other, advocate so-called impact clustering. Notwithstanding the very bombardment of the Earth's early history, followers of impact

support a strike rate that is uniform

and invariable. This is at variance with rival groups of tistswho are promoting an alternative theory of coherent trophism, within which the Earth, for one reason or another, periodically comes under attack from increased numbers of asteroids or comets.

If we are realistically to assess the threat of future impacts to our civilization, then clearly it is vital that we resolve as soon as we can whether the number of collisions continues at its current rate or whether we have a nasty shock i n store somewhere down the line. If the former proves to be correct, we can expect business as usual, meaning a collision with a potential city-destroyer every

years or so, a

kilometre small-country obliterator every ten millennia, a n d a 1-kilometre global impact event every

to

years-depending on whose figures you accept. Fortunately for us, gigantic extinction level such as that

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caused by the

monster that ended the reign of

the dinosaurs 6 5 million years ago, appear to happen every to

million years, so the chances of one striking the Earth soon are tiny. Based upon the above strike

rates, proponents of the threat from asteroids and comets come up with probabilities of dying due to a n impact that really make one think. If you were able to construct a time machine and hurtled forwards to the year 1,000,2002 where you sought out a n d consulted the Centre for Planetary Records you would come up with a fascinating fact. T h e number of people killed in air (and n o doubt space) crashes during the intervening million years-probably between and

billion-would be less than those killed by impact events, which could total 3 billion or more, assuming two or three collisions with 1-kilometre objects. What this amounts to is that during your lifetime your chance of dying due to a n asteroid or comet impact could be twice as great as being killed in an air crash; a pretty sobering thought if ever there was one. Looked at another way, if you gamble, your chance of being killed during an asteroid or comet strike is 750 times more likely than winning the UK lottery. Maybe this scares the wits out of you, but the true situation may actually be worse. If the coherent catastrophists are correct then there are certain periods in the Earth's history when our planet, or perhaps even our entire solar system, travels through a region of space containing substantially more debris than normal, resulting in a significant increase in impact events on all scales.

A number of theories lay the blame for this periodic Page 150

T H E T H R E A T F R O M SPACE

increase in Earth-threatening space debris on the episodic disruption of the so-called Oort Cloud, a great spherical cloud of comets that envelops the entire solar system far beyond the orbit of Pluto. Typically, comets in the cloud travel along such huge orbits, which take some a quarter of the way to the nearest star, that they rarely visit the inner solar system, and then only in ones and twos. However, if some external influence were to interfere with the cloud, so the thinking goes, hundreds or thousands could have their orbits changed encouraging them to plunge Sunwards, greatly raising the threat of collision with the planets-including our own. A number of suggestions have been put forward for how the 34 The Barringer Crater (also known as Meteor Crater) in Arizona is the legacy of a collision with a small asteroid years ago

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Oort Cloud might be periodically disrupted, including due to the passage through the cloud of the mythical a n d much sought after planet

which some scientists think may be

orbiting far beyond frozen Pluto, or to a dark a n d distant stellar companion of our own Sun.

An alternative a n d intriguing theory, known as the Shiva after the Hindu god of destruction a n d renewal, has been vigorously promoted by Mike

of

University and his colleagues, who believe that the great extinctions recognized in the Earth's geological record are the result of major impact events that happen pretty regularly every 26-30 million years.

a n d his colleagues

link this to the orbit of our solar system-including the Earth-about the centre of our Milky Way galaxy, an orbit that moves up and down in a wave-like motion. Every 3 0

million years or so, this undulating path takes the Sun a n d its offspring through the plane of our disc-like galaxy, when the gravitational pull from the huge mass of stars at the galaxy's core provides an extra tug. This, say the school, is

sufficient to disturb the orbits of the Oort Cloud comets to an extent sufficient to send an influx of new comets into the heart of the solar system, dramatically raising the frequency of large impacts on the Earth. It

a few million years now

since our system last plunged through the galactic plane-could a phalanx of comets be heading for us at this very moment? By the time we find out it might very well be too late.

T h e Shiva hypothesis calls for a periodicity operating on truly geological timescales, and for this reason is rarely Page 152

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addressed in discussions of the immediate threat from impact events. Much more relevant to considerations of our own safety a n d survival-and that of our immediate descendants-is a proposal by UK astronomers Victor Clube and Bill Napier that the Earth is struck by clusters of objects every few thousand years, and that our planet took a serious pounding as recently as the Bronze Age-just years

ago. To find out what might cause such a worryingly recent bombardment we need to return to the Oort Cloud in deep-est space. Leaving aside disturbance of the cloud due to the passage of the solar system around the galaxy, normality sees a new comet from the cloud every now a n d again falling in towards the inner solar system-maybe as frequently as every 20,000 years. T h e newcomer is rapidly 'captured' a n d torn apart by the strong gravitational fields of either the Sun or Jupiter, forming a ring of debris spread out along its orbit, but concentrated particularly around the position of the original comet itself. A large comet, broken up in this way, can

'seed' the inner solar system with perhaps a million kilometre sized lumps of rock, dramatically increasing the numbers of Earth-threatening objects, a n d significantly raising the chances of our planet being hit. Clube, Napier, a n d others of this particular coherent catastrophist school propose that the last giant comet from the Oort Cloud entered our solar system towards the end of the last Ice Age-a mere years or so ago-breaking up to form a mass of debris known as the

Complex. Every December the Earth passes through part of this debris stream, resulting in the sometimes spectacular light show put on by the Page 153

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meteor storm, as small rocky fragments a n d gravel-sized stones burn up in the upper atmosphere. These innocuous bits and pieces only represent the tail e n d of the Complex, however, the heart of which contains a 5-kilometre wide Earth-crossing comet known as

a n d at least

accompanying asteroids any one of which would create global havoc if it struck our planet.

T h e distribution of debris along the Complex orbit

about the Sun is rather like that of runners in a race; while the majority are clustered together in a pack, the rest are dotted here and there around the track. Most according to the coherent catastrophists-the Earth's orbit crosses that of the

Complex at a point where there is

little debris, resulting in a pre-Christmas spectacle a n d little else. Every

years or so, the Earth passes through

the equivalent of the runners' pack-and finds itself on the receiving end of a volley of rocky chunks perhaps up to metres across. Benny Peiser, a social anthropologist at Liverpool's John Moores University, thinks such a

bombardment around

years ago led to the fall of many

early civilizations during the third millennium BC. H e a n d others have interpreted contemporary accounts in terms of a succession of impacts, too small to have a global impact but quite sufficient to cause mayhem in the ancient worlds, largely through generating destructive atmospheric shock waves, earthquakes, tsunamis, and wildfires. Many urban centres in Europe, Africa, and Asia appear to have collapsed almost simultaneously around

BC, and records abound

of flood, fire, quake, and general chaos. These sometimes Page 154

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fanciful accounts are, of course, open to alternative interpretation, a n d hard evidence for bombardment from space around this time remains elusive. Having said this, seven impact craters in Australia, Estonia, and Argentina have been allocated ages of

years and the search goes on

for others. Even more difficult to defend are propositions by some that the collapse of the Roman Empire a n d the onset of the Dark Ages may somehow have been triggered by increased numbers of impacts when the Earth last passed through the dense part of the

Complex between

and 600 AD. Hard evidence for these is weak a n d periods of deteriorated climate attributed to impacts around this time can equallywell be explained by large volcanic explosions. In recent years there has, in fact, been a worrying tendency amongst archaeologists, anthropologists, a n d historians to attempt to explain every historical event in terms of a natural catastrophe of some sort-whether asteroid impact, volcanic eruption, or earthquake- many on the basis of the flimsiest of evidence. As the aim of thisvolume is to shed light on how natural catastrophes can affect us all, I would be foolish to argue that past civilizations have not suffered many times at the hands of nature. Attributing everything from the English Civil War and the French Revolution to the fall of Rome a n d the westward march of Genghis Khan to natural disasters only serves, however, to devalue the potentially cataclysmic effects of natural hazards and to trivialize the role of nature in shaping the course of civilization.

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How would you like to die?

If supporters of the

Complex model are to be

believed, a n d I should say now that their views remain very much i n the minority amongst advocates of the impact threat, then we may have only another thousand years or so before a series of blinding flashes and crashing sonic booms heralds the arrival of the next batch of fragmented comet.

Alternatively, we could face oblivion tomorrow or have to wait

years before a city is obliterated or the world plunged into cosmic winter beneath a cloud of pulverized rock. But whenever the skies next fall, how will it affect us?

depend upon three things: (i) size of the object, (ii) how quickly it is travelling, and (iii) whether it hits the land or the ocean. Everything else being equal, the larger the the more devastating a n d widespread will be its effects. To reiterate, a body in the 50-loo-metre size range carries enough destructive power

out amajor city or a

small European country or US state. T h e level and extent of associated devastation will increase progressively with larger impactors until the critical

kilometre size is reached. In

addition to causing appalling destruction on a regional or sub-continental scale, the arrival of a n object of this size will affect the entire planet through engendering a period of dramatic cooling and reduced plant growth. For impactors larger than kilometre the effects on the planet's ecosystems become progressively more severe until mass extinctions wipe out a significant percentage of all species. The kilometre object that struck the Earth off the Mexican coast Page 156

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at the end of the Cretaceous period, 65 million years ago, not only finished off the dinosaurs but also two-thirds of all species living at the time. Even more disturbingly, there is evidence of a major impact event at the end of the Permian period some 250 million years ago that left fewer than per

cent of species alive. In all, at least out of major

tions in the geological record have been linkedwith evidence for large impacts, although as I mentioned in the previous chapter there is a school of thought that plays down the environmental effects of impact events a n d prefers to implicate huge outpourings of basalt lava in the great extinctions of the past.

T h e destructive potential of a chunk of rock hurtling into the Earth is directly related to the kinetic energy it carries, and this reflects not only the size of the object but also the velocity of the collision. Because they travel substantially faster, therefore, impacts by so-called comets,

whose orbits carry them far out into interstellar space, cause more destruction than either Earth-Crossing Asteroids or local comets that follow orbits confined to the heart of the solar system. Both the nature a n d scale of devastation also depends upon whether the

hits the land or the

sea. Two-thirds of our planet's surface is covered by water, so statistically this is where the majority of asteroids a n d comets strike. In such cases, the amount of pulverized rock hurled into the atmosphere might be reduced, compared to a land collision. However, this small benefit is likely to be at least partly countered by the formation of giant tsunamis capable of wreaking havoc across a n entire ocean basin.

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Furthermore, the gigantic quantities of water and salt injected into the atmosphere may severely affect the climate and even temporarily damage the ozone layer. Most of the evidence for the environmental effects of impacts comes from studies of just two events, one small and the other enormous.

At the low end of the scale, in

a small asteroid, esti-

mated at around

metres across, penetrated the Earth's atmosphere a n d exploded less than

kilometres above the

surface of Siberia in a region known as Tunguska. This huge blast, which expended roughly the energy equivalent of 800

Hiroshima atomic bombs, was heard over an area four times the size of the

flattened over

square kilometres

of full-grown forest. The blast registered on seismographs thousands of kilometres distant a n d the atmospheric shock wave was picked u p by barographs time a n d again as it travelled three times around the planet before dissipating. T h e gas a n d dust generated by the explosion led to exceptionally bright night skies over Europe, sufficient-according to one contemporary report-to allow cricket to be played in London after midnight. Because of its inaccessibility, the first Russian expedition did not reach Tunguska until a quarter of a century later, when Leonid Kulik and his team were perplexed by the absence of the huge crater they were expect-ing. Instead they found a circular patch of badly charred a n d flattened trees 6 0 kilometres across, caused by the as

the rock disintegrated explosively due to the huge stresses caused by entry into the atmosphere. As the region was sparsely inhabited, casualties due to the impact were small, Page 158

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35 Trees flattened by the explosion in the atmosphere of a small asteroid over Tunguska (Siberia) in 1908

with perhaps a few killed and up to injured, although

reports are understandably sketchy. Four hours later, however, and the Earth would have rotated sufficiently to bring the great city of St Petersburg into the asteroid's range and the result would have been catastrophic.

The Tunguska events pale into insignificance when compared to what happened off the coast of Mexico's Yucatan Peninsula 65 million years earlier. Here a o-kilometre asteroid or comet-its exact nature is uncertain-crashed into the sea and changed our world forever. Within micro-seconds, an unimaginable explosion released as much energy as billions of Hiroshima bombs detonated Page 159

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taneously, creating a titanic fireball hotter than the Sun that vaporized the ocean a n d excavated a crater 180 kilometres across in the crust beneath. Shock waves blasted upwards, tearing the atmosphere apart a n d expelling over a hundred trillion tonnes of molten rock into space, later to fall across the globe. Almost immediately an area bigger than Europe would have been flattened a n d scoured of virtually all life, while massive earthquakes rocked the planet. T h e atmosphere would have howled a n d screamed as five

times more powerful than the strongest hurricane ripped the landscape apart, joining forces with huge tsunamis to batter coastlines many thousands of kilometres distant.

Even worse was to follow. As the rock blasted into space began to rain down across the entire planet so the heat erated by its re-entry into the atmosphere irradiated the surface, roasting animals alive as effectively as an oven grill, a n d starting great conflagrations that laid waste the world's forests and grasslands a n d turned fully a quarter of all living material to ashes. Even once the atmosphere and oceans had settled down, the crust had stopped shuddering, and the bombardment of debris from space had ceased, more was to come. In the following weeks, smoke and dust in the atmosphere blotted out the Sun a n d brought temperatures plunging by as much as

degrees Celsius. I n the growing gloom

and bitter cold the surviving plant life wilted a n d died while those herbivorous dinosaurs that remained slowly starved.

Life in the oceans fared little better as poisons from the global wildfires and acid rain from the huge quantities of sulphur injected into the atmosphere from rocks at the site Page 160

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of the impact poured into the oceans, wiping out three-quarters of all marine life. After years of freezing conditions the gloom following the so-called Chicxulub impact would eventually have lifted, only to reveal a terrible Sun blazing through the tatters of an ozone layer torn apart by the 36 A reconstruction of the 65 million-year-old Chicxulub impact crater, now buried beneath younger rocks off Mexico's Yucatan Peninsula

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chemical action of nitrous oxides concocted in the impact fireball: an ultraviolet spring hard on the heels of the cosmic winter that fried many of the remaining species struggling precariously to hang on to life. So enormously was the natural balance of the Earth upset that according to some it might have taken hundreds of thousands of years for the post-Chicxulub Earth to return to what passes for normal.

When it did the age of the great reptiles was finally over, leaving the field to the primitive

distant

ancestors-and opening an evolutionary trail that culmin-ated in the rise a n d rise of the human race. But could we go the same way? To assess the chances, let m e look a little more closely at the destructive power of an impact event.

At Tunguska, destruction of the forests resulted partly from the great heat generated by the explosion, but mainly from the blast wave that literally pushed the trees over a n d flattened them against the ground. T h e strength of this blast wave depends upon what is called the peak

that is

the difference between ambient pressure a n d the pressure of the blastwave. In order to cause severe destruction thisneeds to exceed

pounds per square inch, an overpressure that results in wind speeds that are over twice the force of those found in a typical hurricane. Even though tiny compared with, say, the land area of London, the enormous sures generated by a

object exploding low overhead

would cause damage comparable with the detonation of a very large nuclear device, obliterating almost everything within the city's orbital motorway. Increase the size of the and things get very much worse. An asteroid just Page 162

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250 metres across would be sufficiently massive to penetrate the atmosphere; blasting a crater

kilometres across a n d

devastating an area of around

square

that is about the size of the English county of Kent. Raise the size of the asteroid again, to 650 metres, a n d the area of devastation increases to

square kilometres-about

the size of the US state of South Carolina.

Terrible as this all sounds, however, even this would be insufficient to affect the entire planet. In order to do this, a n has to be at least

kilometre across, if it is one of

the speedier comets, or

kilometres in diameter if it is one

of the slower asteroids. A collision with one of these objects would generate a blast equivalent to

million tonnes of

TNT, which would obliterate an area

kilometres a c r o s c

say the size of England-and kill perhaps tens of millions of people, depending upon the location of the impact.

T h e real problems for the rest of the world would start soon after as dust in the atmosphere began to darken the skies a n d reduce the level of sunlight reaching the Earth's surface. By comparison with the huge Chicxulub impact it is certain that this would result in a dramatic lowering of global temperatures but there is n o consensus on just how bad this would be.

T h e chances are, however, that an impact of this size would result in appalling weather conditions a n d crop failures at least as severe as those of the

a

followed the 1815 eruption of Indonesia's Tambora volcano.

As mentioned in the last chapter, with even developed countries holding sufficient food to feed their populations for only a month or so, large-scale crop failures across the planet Page 163

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in the

kilometre size range. Anything bigger a n d photosynthesis stops completely. Once this happens the issue is not how many people will die but whether the human race will survive. O n e estimate proposes that the impact of an objectjust kilometres across will inject sufficient quantities of dust and debris into the atmosphere to reduce light levels below those required for photosynthesis.

Because we still don't know how many threatening objects there are out there nor whether they come in bursts, it is almost impossible to say when the Earth will be struck by an asteroid or comet that will bring to an end the world as we know it. Impact events on the scale of the Chicxulub dinosaur-killer only occur every several tens of millions of years, so in any single year the chances of such an impact are tiny. Any optimism is, however, tempered by the fact should the Shiva hypothesis be true-the next swarm of Oort Cloud comets could even now be speeding towards the inner solar system. Failing this, we may have only another thousand years to wait until the return of the dense part of the Complex and another asteroidal assault. Even if it turns out that there is n o coherence i n the timing of impact events, there is statistically n o reason why we cannot be hit next year by an undiscovered Earth-Crossing Asteroid or by a period comet that has never before visited the inner solar system. Small impactors on the Tunguska scale struck Brazil in

and Greenland in

a n d will continue to pound

the Earth every few decades. Because their destructive foot-print is tiny compared to the surface area of the Earth, however, it would be very bad luck if one of these hit an urban Page 165

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area, a n d most will fall in the sea. Although this might seem a good thing, a larger object striking the ocean would be very bad news indeed. A

rock landing in the Pacific

Basin, for example, would generate gigantic tsunamis that would obliterate just about every coastal city i n the hemisphere within

hours or so. T h e chances of this happening are actually quite high-about

per cent in the next

years-and the death toll could well top half a billion.

Estimates of the frequencies of impacts in the kilometre size bracket range from

to

years, but the

youngest impact crater produced by an object of this size is almost a million years old. Of course, there could have been several large impacts since, which either occurred in the sea or have not yet been located on land. Fair enough you might say, the threat is clearly out there, but is there anything on the horizon? Actually, there is. Some 13 asteroids-mostly quite small-could feasibly collide with the Earth before 2100. Realistically, however, this is not very likely as the probabilities involved are not much greater than in

although bear in mind that these are pretty good odds. If this was the probability ofwinning the lottery then my local agent would be getting considerably more of my business. There is another enigmatic object out there, however. Of the or so

Near Earth Asteroids spotted last year, one-designated at first as if it might actually hit us. T h e object is small, in the

metre size range, a n d its orbit is so similar to the earth that some have suggested it may be a booster rocket that sped one of the Apollo spacecraft on its way to the Moon. Whether h u n k of rock or lump of Page 166

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originally scraped into category

events meriting

careful monitoring. Let's hope that many years elapse before we encounter the first category

event-defined as 'a cer-

tain collision with global consequences'. Given sufficient warning we might be able to nudge an asteroid out of the Earth's way but due to its size, high velocity, and sudden appearance, we could do little about a new comet heading in our direction.

Facts

Perhaps

or more asteroids a kilometre or greater in diameter regularly cross the Earth's orbit and about a third of these will end their lives by colliding with our planet.

Collision with a 1-1.5-kilometre

could result in

the deaths of a quarter of the world's population.

We may get just six months warning of a future comet impact.

An asteroid large enough to destroy London, or Paris strikes the planet a couple of times a century.

Ancient impacts may have wiped out up to go per cent of all life on Earth.

There is a

per cent chance of a

object hit-

ting the Pacific Ocean in the next

years.

According to some, we only have to wait another thousand years or so before our planet begins to take another pounding from space

Page 168

Epilogue

Now

been ten thousand years

M a n has

a

tears

For what he

knew

Now

through

I n

Zager

Evans

P ondering in isolation upon the consequences of global warming, the imminence of the next Ice Age, or the timing of a future super-eruption or asteroid impact can engender fleeting concern. Consideration the

future threats to our planet and our race is quite capable, however, of contributing to bouts of severe depression. Let m e summarize our current position. We are now well into a cycle of warming that is certain to lead to dramatic geophysical, social, a n d economic changes during the next hundred years that will impinge-probably largely detrimentally-on everyone. At the same time our planet is teetering on the edge of the next Ice Age, whose start global warming might actually bring forward, but which is likely to arrive within the next several thousand years even without our help. Asteroids sufficiently large to wipe out a quarter of the human race continue to hurtle across the Earth's orbit undetected, while who knows when we will detect the next great comet coming our way. There are now so many of us Page 169

that the next giant tsunamis or volcanic super-eruption cann o t fail to result in millions of deaths a n d the enormous disruption of our so-called advanced global society. So inter-connected is our social a n d economic framework a

single quake in Japan could lead to global economic disaster.

There are other trends too that will ensure a n end to the world as we know it, and within this century. Although the world's population is still rising, the rate started to slow in 1968 and numbers will peak at around g billion-half as great again as today-in about

After that they will

begin to fall and will be down to 8.4 billion just 3 0 years later.

Welcome as this trend is, its legacy will be an ageing population a n d a so-called 'grey' future. By the e n d of the century a n extraordinary

per cent or so of people in Japan a n d western Europe will be 6 0 or older, and a full third of the planet's populationwill be over this age. In aworldwhere the elderly hold increasing sway over the young, some believe that intergenerational conflicts may come to dominate the political scene.

Not only will the future of our descendants be greyer, also be dull and barren. I n one of the greatest mass extinctions ever, our activities are currently wiping out between 3,000 and 30,000 species a year, from an estimated total of just

million. Up to one-third of flowering plants could be at risk, while between

a n d

per cent of all animal species

could disappear before the chimes ring in the new century on January 2100. As more and more species are obliterated their places will quickly be taken by the pests, weeds, a n d diseases that live cheek-by-jowl with the human race. Instead Page 170

of a world of gorillas, pandas, birds of paradise, and corals, our descendants will have to make do with rats, cockroaches, thistles, and nettles. Furthermore, biodiversity is such a fragile thing-tenderly and incrementally reared by that it may take million years or more for it to restore itself.

In the meantime, we will have committed an estimated trillion of our descendants to life on a dull and-in terms of variety-largely lifeless planet. Just as importantly, we are actually playing God with evolution itself and the entire future prospects of life on Earth. By wiping out the bulk of species that exist today, we are destroying much of evolution's raw material and severely limiting the planet's ability to generate the species of the future. For millions of species throughout geological time the end of the world has already come, and our activities are ensuring that the same fate will shortly face many of the life forms with which we currently share our planet.

T h e picture I am painting of the future, seems to

get worse a n d worse. An ageing population, perhaps lacking the dynamism a n d innovation of the past, battling with climate change a n d its consequences a n d ensuing economic, political, a n d social upheaval, a n d struggling-maybe too late-to right the environmental wrongs wrought by their ancestors-us. Somehow, against this background Carter's 'doom soon' scenario does not sound so far-fetched.

Others too have come to the conclusion that things must come to a dramatic head soon. Anders Johansen and Didier Sornette of the University of California, for example, have recently predicted-on the basis of trends in population a n d Page 171

economic a n d financial indices-that some sort of abrupt witch to a new 'regime' will occur in years or so, the

nature of which remains to be seen, but which is unlikely to be pleasant.

Probably the only piece of good news that can be taken away from my brief look at the e n d of the world know it

is that although this is going to happen- and soon-the survival of our race seems to be assured, for now at least.

Leaving aside the possibility of a major comet or asteroid impact on a scale of the dinosaur-killer 65 million years which only happen every few hundred million years-it is highly unlikely that anything else is going to wipe out every single last one of

6 billion plus-in the foreseeable future. Even the replacement of the world with which we have become so familiar with one of sweltering heat or bitter cold might n o t seem as scary for those of our descendants likely to be in the thick of things. After all, we are a remarkably adaptable species, and can change to match new circumstances with some aplomb. Familiar 'worlds' have certainly ended many times before, as n o doubt a centenarian born and raised while Queen Victoria sat on the throne of the United Kingdom, a n d who lived to see man land on the moon, would testify. T h e danger is, however, that the world of our children and those that follow will be a world of struggle a n d strife with little prospect of, and perhaps little enthusiasm for, progress as the Victorians viewed it. Indeed, it would not be entirely surprising if, at some future time, as the great coastal cities sink beneath the waves or below sheets of ice, the general consensus did not hold that there Page 172

had been quite enough progress thank you-at least for a while.

While I have tried in these pages to extrapolate current trends and ideas to tease out and examine somewhat depress-ing scenarios for the future of our planet a n d our race, I am sure that, to some extent at least, you would be justified in accusing me of a failure of the imagination. After all, I have rarely looked ahead beyond a few tens of thousands of years, and yet our Sun will still be bathing our planet in its life-giving warmth for another

billion years or more. Who knows,

over that incomprehensible length of time, what Homo a n d the species that evolve from us will do a n d become.

O u r species and those that follow may be knocked back time and time again in the short term, but provided we learn to nurture our environment rather than exploit it, both here on Earth-before the Sun eventually swallows it up-and later, perhaps, in the solar system and the galaxy and beyond, then we have the time to do and be almost anything. Maybe now is the right time to start.

Page 173

Page 174

Page 175

Page 176

Page 177

Page 178

Further Reading

Alexander,

Natural Disasters. UCL Press.

Edward. Tsunami: The Underrated Hazard. Cambridge University Press. 2001.

Burroughs, William.

Climate Change. Cambridge University Press.

2001.

Dawson,

G. Ice Age Earth. Routledge.

Intergovernmental Panel o n Climate Change (IPCC) Working Group Climate Change

Impacts, Adaptation, a n d Vulnerability.

Cambridge University Press.

Lamb, H. H. Climate, History, a n d the Modern World. Routledge.

Legett,

T h e Carbon War. Penguin.

Lovelock,

Gaia: The Practical Science of

Medicine.

Gaia.

1.

McGuire, Bill. Apocalypse: A Natural History of Global Disasters.

McGuire, Bill. Raging Planet: Earthquakes, Volcanoes a n d the Tectonic Threat to Life o n Earth.

2002.

McGuire, W. J., Kilburn, C. R. J., a n d Mason, I. M. Natural Hazards a n d Environmental Change.

L. The Atlas of the World's Worst Natural Disasters. Dorling Kindersley.

Steel,

Target Earth. Readers Digest.

Zebrowski, E. Jr. Perils of a Restless Planet: Scientific Perspectives o n Natural Disasters. Cambridge University Press.

Page 179

Page 180

Index

accretion process

hurricane alley

acid rain

Overturning Circulation 84,

aerosols

African plate

atmosphere

ageing population

auroras 82

agriculture

81,

Australia

Alabama

axial rotation

Alaska

53

Bangladesh

animal species 56,

deaths caused by storm

flooding

Antarctic ice sheets

population 28

anthropogenic warming

rising sea levels and

84,

alsoglobal warming

Barringer, D. M.

Apollo

Barringer Crater, Arizona

166

Arctic

8 7

basalt lava

Argentina

Arizona

Bay of Bengal

Armero, Columbia 23

Straits

asteroids

6, 8, 25-6,

earthquake, India

Chicxulub impact

biodiversity 56,

earth-crossing

blast waves

162

Brazil 18,

potential impacts

Bronze Age 153

Complex

building codes 22,

buildings

badly constructed urban 28

astronomy

collapsed by volcanic ash 23

Atlantic Ocean

during earthquakes 22, 120,

giant tsunamis

121, 123, 127,130

Page 181

C

C (Contraction

climate change

46

Convergence) 62

following volcanic eruption

Calcutta, India

increased natural disasters

California

29-30

Little Ice Age

Cambrian period 6

precipitation

volcanoes

Islands

climate records

43

carbon dioxide

Clube, Victor and

Bill

biggest polluters of

coastal areas 28, 45

high concentrations of

erosion

39

ice ages and

tsunamis

166

techno-fix tendency

coherent catastrophism

Caribbean

18,

84,

Columbia 23

99

Comet Shoemaker-Levy 26,

Carter,

catfish

comets

8,

Chicxulub impact (near Mexico)

Chicxulub impact

Chile

long-period

China

Oort Cloud

earthquakes

Shoemaker-Levy 26,

river floods

plate margins

13

Shanghai population

constructive plate margins

chlorofluorocarbons 38

consumption 56

quake

continental plates

also

cities

plate tectonics

coastal

convection currents

mega 28-9, 1 2

coral-reefs 56,

at risk from giant tsunamis

cosmic winter 26,

156,

civil defence

craters 26,

civil strife go,

clean air laws 43

Cretaceous period

Page 182

Croll,

DNA

crop failures

doomsday argument

crop yields

Clyogenian period 69

Cumbre

volcano

Earth

Islands) 15-18

bombardment from space 26,

cyclones

Dark Ages

post-Chicxulub impact

Day, Dr Simon

rotation

death tolls

Snowball

earthquakes 22, 1 2

space debris impacts

firestorms

temperature 36, 38,

also ice

floods 18

ages

impact events

earthquakes

landslides

following Chicxulub impact

23

natural disasters cumulative 27

g

flows

intraplate 2 2

tsunamis

Japan

volcanoes 96, loo,

landslides caused by

Trap flood basalt

large sea-level changes

plate margins

2 2

dengue fever 56

prediction of

132

plate margins

13,

tsunamis

2 2

Turkey

developing countries

(Earth-Crossing Asteroids)

economic toll of natural

143,144,

disasters

55

(Earth-Crossing Comets)

famine

population growth

economic costs

tackling global warming

giant tsunami

urbanization 28

Great

Earthquake

Dhaka, Bangladesh 28,

natural disasters

20,

Dickens, Charles 81

54-5

dinosaurs 6, 8,

of next Tokyo earthquake

disease 56,

Page 183

economic migration

Germany

ecosystems 56,

geysers

El

volcano (Mexico)

Gilbert, Grove

E1

Islands)

glaciation

68,

53

80

E1 Paso (Texas)

Global Commons Institute

electrical charges

(London) 62

(extinction level events)

Global Conveyor 86

Global Positioning System

Encke (ECC)

global warming

Equator

adapting to 59-60

emption

Little Ice Age

ocean currents

Estonia

return to

conditions 84

Eurasian plate

glowing avalanches

evolution

Great Depression

exploration g

Great Kanto Earthquake

Faeroe Islands 8 8

Great Storm (southern England

famine

55, go,

164

fault lines

greenhouse gases

firestorms

C & C 62

fish

effect on warm ocean currents

flood basalt emptions

84-5

flood plains 28

globalwarming and

food shortages

(marine organisms)

Kyoto Protocol

62

86

Greenland

forcing mechanism 73

icesheets

57, 87, 88

France, winter storms in

impactors

(Shelley)

Gmithuisen,

frost fairs

81, 83

Galileo unmanned probe

India

Ganges river system

Gulf of Mexico

gas hydrates 5 8

84, 86

Page 184

Halley's Comet

insurance

Hawaii

113

conflicts

health problems caused by

International Federation of Red

global warming

Cross

volcanic ash

intraplate quakes 2 2

volcanic gases

IPCC (Intergovernmental Panel

Himalayas

on Climate Change)

Hollywood films 138

Honduras

Ireland 84

hot springs

iron g

Hubble Space Telescope

Istanbul

human race

162,

Italy 2 2

Hurricane

Izmit region, Turkey

Hurricane Mitch

hurricanes

18,

51,

Japan

earthquakes

hydrofluorocarbons 38

tropical storms

volcanic activity

Java 86,

and Sornette,

ice ages

Didier

effect on 84-5

Jupiter 26,

Little

Pakistan 28,

1 2 2

next 67-90, 169

Kentucky

impact events

Hawaii 22,

clustering

Kobe earthquake

craters 26,

effect of

96

Torino Scale

Leonid

India

Kyoto Protocol

62

earthquakes

22, 1 2

flooding

La

Islands)

volcanic activity

Indian Ocean

16,

Lagos

Indonesia

loo, 163

Lake

78, 80

industrialization 8 1

Lake

(New Zealand)

Page 185

Lanai (Pacific Ocean)

mass extinctions

xii, 8,

land bridges

dinosaurs

landslides

28

early civilizations

earthquakes causing 2 2

impact events

large sea-level changes

Toba emption

mountainous regions 53

Loa, Hawaii

13

submarine 5 8

Minimum 82

tsunamis

Medieval Warm Period 81, 84

volcano lateral collapse

28-9, 1 2

112-19

meltwater 78

lava

Memphis, Tennessee 3

(living space)

,

Mexico

leisure activities 56

Mexico City 28,

1 2 2

Leslie, John viii

Miami

137

Micronesia (Pacific Ocean)

lithosphere

13,

Mid-Ocean Ridge system 13,

Little Ice Age

migration

Loma

earthquake,

economic

California

land bridges

Lomburg, Blom 36

south to escape Ice Age go

London

Milankovitch, Milutin

long-period comets

Milankovitch Cycles

76, 85,

Los Angeles, California

Lothar, France 18

Milky Way

minerals

magma 8,

Minoan civilization 96

11- 12

Miocene period

magnetic fields

g

Mississippi River

malaria

56

Missouri River

Islands

mitochondria

mammals 162

molten rock

Mammoth, California 3

Mont

volcano

mantle

(Martinique)

mantle plume 13

volcanic emption

marine organisms 86

99

Martinique

Moon

Page 186

Mount St Helens emption

northern hemisphere 73, 74, 79,

(1980)

mountainous regions 4 6 7 , 53-4

Northridge earthquake,

Mozambique

California

1,

Norway 58

Mumbai, India 28,

nuclear war

Munich Re (reinsurance

nuclear winter

company)

oceanic plates

alro

natural disasters

plate tectonics

economic cost

16, 18, 20,

oceans

circulation system 80, 84-5,

explanation for historical

events

E1 Niiio 53

increasing rate of

impact events

plate margins and

Mid-Ocean Ridge system

potential comet or asteroid

plans for dumping atmospheric

impact

carbon dioxide in

World Disasters Report on

thermal expansion of

alro earthquakes;

Japan 128

floods; impact events;

Older

cold phase 78

landslides; volcanoes

Oort Cloud

navigation g

Ordovician period

del

volcano

India

(Columbia) 23

ozone layer

mountain

Andes)

Pacific Ocean

Pacific plate

New Zealand

Chris and Self,

98

Panama Isthmus

nickel g

New Guinea

nitrous oxide 37, 39,

tsunamis 2 1, 2 2

North America 78,

alro

volcanic activity 23, 96,

Canada; United States

North Anatolian Fault (Turkey)

parabolic orbits

volcano (Alaska)

47,

74

peak

Page 187

Benny

radon gas 129

perihelion

Raffles, Sir Stamford

Permian period

rainfall

El

effect on 53

(Potentially Hazardous

floods

Asteroids) 8

landslides

54

Philippine plate

Mike

Philippines 11,

96,

Mike and

photosynthesis

Stanley

Pinatubo, Philippines

rationing

recycling 60, 62

plate tectonics

23,

Red Crescent Societies

reefs 56,

renewable energy sources 60, 62

Plymouth,

resource exploitation

polar ice cores 37

Reunion island (Indian Ocean)

polar regions 46-7,

8 7

Richter Scale 123

also greenhouse gases

Ring of Fire (Pacific Rim)

population

Ritter Island volcano (Papua New

ageing

Guinea)

bottlenecks

river floods

growth 27-9

Roman Empire

Ice Age go

Russia,

precession 73

precipitation

rainfall;

Bay, Japan

snow

San

Fault, California

Pyrenees 53

2 0

flows

Santa

California

satellites

period

science

148

Scotland

emption, Papua New

sea levels 16,

Guinea

falling

potential to trigger seismic

radiation g

activity

radioactivity 8, g,

47,

Page 188

seasons

72-4

Ronald and Hall,

Second World War

Shanghai, China

stratosphere 82,

Shelley, Mary

Stromboli, Italy 2 2

Shensi province, China

subduction process

Shiva hypothesis

165

sulphur dioxide

shock waves

sulphur gases

loo,

Shoemaker,

and Carolyn

sulphuric acid loo,

86, loo,

Japan

Sumbawa, Indonesia

Siberia

silicates g,

silicosis

after Chicxulub impact

organisms

asteroids

Sissano, Papua New Guinea 2 2

higher output of

Smart, W. M.

sunspot cycle

Complex orbit

Snowball Earth 69-70,

Bay, Japan 128

solar radiation 69, 73, 98

Svalbard 84

solar system

Switzerland 53

asteroids

comets

Taiwan

space debris in

emption, Indonesia

solar wind

Complex

Solomon Islands

southern hemisphere 73

volcano, Papua New

space debris

Guinea

'techno-fix tendency'

Foundation

temperature falls

Minimum 82

St Lawrence River 78

cosmic winter 26,

156,

St Moritz, Switzerland 53-4

St Pierre,

Earth's rotation

Storegga Slides 5 8

effects on population

storm surges 28,

ice ages 75-83,

storms 16, 18,

ocean currents 86-9

Page 189

sulphuric gas

(Near Earth

volcanic gas

Asteroid)

temperature rises

typhoons

accelerate next Ice Age 68

IPCC report on 45-9

ultraviolet spring 162

mountainous regions

53-4

uniformitarianism

47

United Kingdom

primordial Earth 8

coastal erosion

sea 51

flooding

Tenerife

Gulf Stream 84-5

Tennessee 2 0

research into asteroid impact

termites

Thames, River

81, 8 3

winter storms 18

Greece 96

United States

thunderstorms

earthquakes

Tilghman,

greenhouse gas emissions

Toba (Sumatra)

hurricanes

Tokai earthquake 128

Meteor Crater

Tokyo-Yokohama conurbation,

potential giant tsunami

Japan 122-31

river floods

Tonga (Pacific Ocean)

San

Fault, California

Torino Scale

10

tornadoes

Spaceguard projects

tourism 56

tornadoes 18, 2 0

period

tropical storms

tropical cyclones

23

volcanic activity 22, 57,

troposphere 8 3

tsunamis

2 1 , 2 2 , 28,

volcano, Japan

urbanization 28-9

impact events

submarine landslides causing

vegetation 56,

.

impact

volcano lateral collapse

impact event

Mount St Helen's

asteroid, Siberia

(Volcanic Explosivity Index)

Turkey

Turner, M. W.

Venezuela 27

Page 190

volcanic winter xi,

98,

wars go

water shortages

volcanoes 3,

6, 22-3

waves

tsunamis

ash

West Antarctic Ice Sheet

climate

wind

ending Ice Age

cyclones

23

flood basalt eruptions

hurricanes

18,

61,

large sea-level changes

speeds

lateral collapse

storms 16, 18,

Little Ice Age 82

tornadoes 18, 2 0

plate margins

winter sports 56

flows

winter storms 18

super-eruptions xi-xii,

World Disasters Report

44

widespread effects of

World Meteorological

100

Organization

5 3

in

New

Guinea)

Yellowstone, Wyoming

Ward,

and Day, Simon

Younger

cold phase

Page 191

Document Outline

- A Guide To The End Of The World : Everything You Never Wanted To Know

- Front Cover

- Title Page

- Copyright

- Foreword

- Table Of Contents

- List Of Illustrations

- 1 A Very Short Introduction To The Earth

- Danger: Nature At Work

- The Earth: A Potted Biography

- Hazardous Earth

- Natural Hazards And Us

- Facts To Contemplate

- 2 Global Warming: A Lot Of Hot Air? 33

- Debate, What Debate?

- The Pat Global Warming Experiment

- Hothouse Earth

- The Good, The Bad, And The Downright Mad

- Facts To Fret Over

- 3 The Ice Age Cometh 65

- How To Freeze A Planet

- Charles Dickens, White Christmases, And The Little Ice Age

- A Very British Ice Age

- Out Of The Frying Pan Into The Fridge

- Facts To Fret Over

- 4 The Enemy Within: Super-eruptions, Giant Tsunami, And The Coming Great Quake 93

- Hell On Earth

- A Watery Grave

- The City Waiting To Die

- Facts To Fret Over

- 5 The Threat From Space: Asteroid And Comet Impacts 135

- The Astronomical Event Of The Century

- The Cosmic Sandstorm

- When Worlds Collide

- How Would You Like To Die?

- Facts To Fret Over

- Epilogue 169

- Appendix A: Threat Timescale 175

- Appendix B: Geological Timescale 177

- Further Reading 179

- Index 181