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The world of 2100 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 2001 World Disasters Report, the International Federation of Red Cross and Red Crescent Societies reveals 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 and 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 and more people will starve as annual rains fail year after year and huge regions of Africa and Asia fall within the grip of drought and 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 and 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 and 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, 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 in 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 not sound much, consider that just 4 or 5 degrees Celsius mean the difference between full Ice Age conditions and our current climate. The transition between the two involved huge changes in the Earth's environment, not only in the climate and 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, and support 6 billion or more souls, rather than a few million, and 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. The polar regions and mountainous areas with permanent snow and ice are already suffering, and warming will continue to exact a severe toll here. Over the last loo years there has been a 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 and 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 and 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 (ppm). 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 and 20 centimetres during the twentieth century, and this rise is expected to escalate drastically in the coming hundred years, with sea levels predicted to be 40 centimetres and perhaps over 80 centimetres higher by 2100. Most of the recent and 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

180 120W 60W 0 60E 120E 180

I |1 |2 □□ 3 □□ 4 □□ 5 I 16+ io Annual mean change in temperature between now and s100 (all temperatures in degrees Celsius)

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

11 Devastating floods, such as those which affected Mozambique in 2000, are likely to become more frequent as the Earth continues to warm

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, and more rainstorms, floods, and 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 and 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. The Atlantic's 'hurricane alley' is likely to get much busier in the next halfcentury, and predictions made in summer 2001 in the journal Science point to more strong hurricanes battering the Caribbean islands and the south-eastern and Gulf coasts of the USA. So far few are prepared to stick their necks out and 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 and 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 and 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 not 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 and which will undoubtedly be exacerbated by rising sea levels and storms.

It also looks as if global warming is leading to more

1 2 Hurricane Andrew caused severe destruction in south Miami in 1992. More and bigger hurri canes could be on the way frequent El Niño events; the second largest climatic 'signal' after the seasons. An El Niño 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. The World Meteorological Organization has just announced that another El Niño will be with us in 2002, bringing heavy rains to the western USA and central and southern America and drought to parts of Africa and Asia. The 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 and 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 and the skies that become increasingly agitated: the planet's crust will also join in. Already warmer temperatures in mountainous regions such as the Alps and the Pyrenees are causing the permafrost to melt at higher altitudes, threatening villages, towns, and ski resorts with more frequent and more destructive landslides. As the melting ice weakens the mountains, Switzerland is already experiencing more rockfalls, landslides, and 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 and 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 in just the last 15 years. Continued warmingat this rate could destabilize mountain tops right across the planet, making life both difficult and 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 and 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, and drought— an amazing 1in 30 of the planet's population, and 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 in 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 and the fabric 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, and increasing pollution, there is no question that the impact of global warmingwill be terrible. One 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 and Africa. Alongside this, crop yields are forecast to fall in tropical, subtropical, and 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 20 years ago and 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 mosquitoes to survive and breed. In the tropics there will be an 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 and 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 and atolls, mangrove swamps, and sensitive polar and alpine ecosystems will all struggle to survive and adapt, and 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, and 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 and 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 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, and huge landslides to collapse from continental shelf regions. The 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.

The 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. The accumulation of gases from the 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 destabil-ization and 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 and continues unhindered for the next few centuries then it looks as if things may start to get very exciting indeed.

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