Ten years ago, global warming was a problem far away on the horizon, something for our grandchildren to worry about. A problem that, as responsible citizens, maybe we should tackle soon. But this autumn the southeast of England was battered by the latest in a series of storms causing a once in 30-year flood to occur twice in one month. In response, UK Deputy Prime Minister John Prescott called a meeting of local authorities, the Environment Agency and emergency services to consider how Britain will prepare for these global warming-induced extreme weather events. Moreover, October this year saw the release of a draft United Nations assessment of climate change document which clearly states that the warming trends observed over the last 50 years are due to human pollution of the atmosphere, strengthening previous statements by the Intergovernmental Panel on Climate Change (IPCC). It appears there is a consensus that global warming has hit us with avengeance.

The evidence

Global warming is caused by the release of carbon dioxide and other greenhouse gases through burning fossil fuels and other industrial processes, as well as changes in land use such as deforestation. Ground temperature records for the last 50 years have shown a general increase of about 0.5°C. This alone does not prove the climate system has changed; this has been shown by much more recent changes. For example, the recent storms which hit Italy and England towards the end of this year are strong signals that the European climate is changing. On average, British birds nest two weeks earlier than 30 years ago. Insect species - including bees and termites - that need warmer weather to survive are moving north; some have already crossed the Channel from France to the UK and it is now warm enough for malaria mosquitoes to survive and breed in Sussex. Glaciers in Europe are in retreat, particular in the Alps and Iceland. Icecaps throughout the world are getting smaller; for example there was even a hole in the ice directly above the North Pole this summer.

The last 50 years have also seen a marked increase in the average wave height in the Atlantic, demonstrating a significant increase in the number of storms hitting Europe. Taking all these changes into consideration, the future effects of global warming can be split in to two major insurance nightmares; sea level rise and increased storminess.

Rising sea level

The IPCC predicts that under a “business as usual” scenario (i.e., continued increase of burning fossil fuels), sea level could rise between 30cm and 100cm in the next 100 years, primarily due to the thermal expansion of the oceans. This is a major concern to all coastal areas as it will decrease the effectiveness of coastal flood defences and increase the instability of cliffs and beaches. In Britain, the response to this danger of ever-increasing sea levels has been to add another few feet to the height of sea walls around property on the coast, abandoning some poorer quality agricultural land to the sea as it is no longer worth the expense of protecting it and adding additional legal protection to our coastal wetlands which are nature's best defence against the sea. Globally there are countries, for example small island and river delta-based nations, which face a much more dire situation than Britain.

If we first consider small island nations such as the Maldives in the Indian Ocean and the Marshall Islands in the Pacific a one metre rise in sea level would flood up to 75% of the dry land, making the islands uninhabitable. However, there is a different twist to the story if we consider nations with a significant portion of their country on river deltas, such as Bangladesh, Egypt, Nigeria and Thailand. A World Bank report in 1994 concluded that other human activities on the deltas were exacerbating the effects of global warming by causing the deltas to sink.

In the case of Bangladesh, over three-quarters of the country is within the deltaic region formed by the confluence of the Ganges, Brahmaputra and Meghna rivers. Over half the country lies less than 5m above sea level, so flooding is a common occurrence; during the summer monsoon a quarter of the country is flooded. Yet these floods, like those of the Nile, bring with them life as well as destruction. The water irrigates and the silt fertilises the land; the fecund Bengal Delta supports one of the world's most-densely populated areas, over 110m people in 140,000 square kilometres. But the monsoon floods have been getting worse throughout the 1990s. Every year the Bengal Delta should receive over 1bn tons of sediment and 1,000 cubic kilometres of fresh water. This sediment load balances the erosion of the delta both by natural processes and human activity. However, the Ganges River has been diverted in India into the Hooghly Channel for irrigation. This reduced sediment input is causing the delta to subside.

Exacerbating this is the rapid extraction of freshwater from the delta for agriculture and drinking water. In the 1980s, 100,000 tube wells and 20,000 deep wells were sunk, increasing fresh water extraction sixfold. Both these projects were aimed at increasing the region's economy, but produced a subsidence rate of over 2.5cm per year in parts of the country, one of the highest rates in the world. From the worst case scenario using estimates of subsidence rate and global warming sea level rise, the World Bank has estimated that by the middle of the 21st century the relative sea level in Bangladesh could have risen by as much as 1.8m. In a worse case scenario, it estimated this would result in a loss of up to 16% of land, supporting 13% of the population and producing 12% of the current gross domestic product (GDP) - money that Bangladesh can ill afford to lose. Things are even worse as this scenario does not take any account of the devastation of the mangrove forest and the associated fisheries. Moreover, increased landward intrusions of salt water would further damage water quality and agriculture. Though Bangladesh is the worst case globally, similar changes are observed at all other major delta regions.

IPCC estimates only consider the thermal expansion of the ocean and do not take into account the possibility of the world's ice sheets and glaciers melting. If all the ice sheets melted, their contribution to sea level rise would be:

  • Mountain glaciers = 0.3m;

  • Western Antarctic ice sheet = 8.5m;

  • Greenland = 7m; and

  • Eastern Antarctic ice sheet = 65m.

    NASA satellite measurements suggest both Greenland and the Western Antarctic ice sheets are shrinking, suggesting we could have some big surprises storing up for the future.

    Though the best way to prevent global warming is to cut emissions, its effects are already having an impact, so we must plan for sea level rise. This way, many valuable areas can be protected and insurance losses kept to a minimum. Adaptation to the rapid sea rise is by far the cheapest long-term option, if global warming cannot be prevented. The diagram below shows some key ways suggested by IPCC that we could protect our coastlines and reduce damage to property and infrastructure. These need to be instigated at a governmental level and it is in the interest of the insurance industry to lobby for this forward planning. This must happen now, as the diagram on the next page shows how long it can take to make these changes, many of which will take at least the next 50 years to implement.

    Increasing storminess

    We know from historic records that during periods of rapid climate change weather patterns become erratic and the number of storms increase. The Little Ice Age, which lasted from the end of the 16th century to the beginning of the 18th century, is mainly remembered for ice fairs that were held on the frozen River Thames in London. However, what is not remembered is that going into and coming out of the Little Ice Age produced some apocalyptic tempests. For example, at the end of Little Ice Age, as climate was finally warming, in 1703 there was the worst recorded storm in British history, which killed over 8,000 people.

    Similarly there is evidence for increased storminess over the last 50 years. Wave height in the North Atlantic Ocean has been monitored since the early 1950s, from lightships, ocean weather stations and, more recently satellites. Between the 1950s and the 1990s the average wave height increased from 2.5m to 3.5m, an increase of 40%. Storm intensity is the major control on wave height so we have clear evidence for a major surge in storm activity over the last 40 years.

    However, global warming is especially bad news for hurricanes. In August 1992, Hurricane Andrew hit the US and caused record damage, estimated at $20bn. In 1998, Hurricane Mitch hit Central America and killed at least 20,000 people, made 2,000,000 people homeless and set back the economic growth of the region by decades. These are, not isolated freak storms, however; the last ten years repeatedly have seen the worst hurricanes around the world for a century. Hurricanes and their cousins cyclones and typhoons form in the tropics when the sea surface temperature is at least 26°C down to 60m below the surface. All it then takes is a further increase of 1°C in sea surface temperature to reduce atmospheric pressure enough to start the convective cell. This rapidly rising air, which sucks in air at sea level and produces the powerful hurricane vortex. With increasing global warming, achieving the critical temperatures in the oceans will be easier than ever before, spawning more hurricanes with more energy to be unleashed upon our coastlines.

    The message is clear. The Caribbean and US in our ‘Greenhouse World' will be hit more often and by bigger, meaner hurricanes. The good news is that by knowing this, it should possible to improve the evacuation procedures and consequently save lives. As an illustration, when 1988's Hurricane Gilbert - the same size and power as Hurricane Mitch a decade later - hit Jamaica, the evacuation procedures were so effective that only 44 people died (11 of whom were shoot by police for looting). However, the damage to property was huge as most of the emphasis was on saving lives not preventing economic loss. Now in Jamaica, all new buildings must be able to withstand three-second gusts of up to 200kph without serious damage and the easily damaged aluminium roofs are slowly being replaced.

    This intensification of the climate system is, however, not just isolated to the North Atlantic. There is evidence that the El Niño - Southern Oscillation (ENSO) is speeding up. The ENSO is caused by the fluctuating balance between the warm and cold surface waters, thus atmospheric pressure, either side of the Pacific. El Niño should return every three to seven years, but since 1991 it has returned in 1991-2, 1992-3, 1994-5 and 1997-8. The 1997-8 El Niño conditions were the strongest on record and caused droughts in the southern US, East Africa, northern India, north-east Brazil and Australia. In Indonesia, forest fires burned out of control in the very dry conditions resulting from the El Niño episode. In California, parts of South America and east central Africa there were torrential rains and terrible floods.

    Hot off the press results in the leading journal Nature, scientists at the University of Colorado have shown that El Niño has changed and the only culprit is global warming. By drilling a 150-year long core from the coral reefs in the Western Pacific, they were able to obtain a continuous record of the sea surface temperature beyond our historic records. There have been two major changes in the frequency and intensity of El Niño events. First was a shift at the beginning of the 20th century from a 10-15 year cycle to a three-to-five year cycle. The second shift was a sharp threshold in 1976 when a marked shift to more intense and even more frequent El Niño events occurred. These are sobering results considering the huge weather disruption and disasters caused by last year's El Niño. Modelling results also suggest that the current “heightened” state of El Niño can permanently shift weather patterns. For example, it seems that the drought region in the US could be shifting eastward.

    Conclusion and future opportunities

    While most of the international political focus has been on reducing carbon dioxide emissions to avert future global warming, governments and the insurance industry must work on the equally important second area of work - local adaptation to the effects of global warming. For example, in the UK there have been (so far largely unheeded) warnings about not building on flood plains, plus unreported changes to building regulations so that tall buildings can withstand higher wind speeds. So things need to change.

    As to future opportunities, the global insurance market should keep an eye on the global warming negotiations which were started at the Kyoto meeting and continued albeit unsuccessfully in mid-November in The Hague. Leaders of all the world's nations are aiming to ratify the international climate change agreement that will stabilise carbon dioxide emissions at 1990 levels. Under discussion is what is each country's carbon budget, and how both emissions and increased storage of carbon in forests and plants will be taken into account. It has already been discussed that these carbon credits could be bought from another country, reducing the required cuts in emissions. So, for example, the US could increase its carbon dioxide emissions but buy the right to help another country manage its forests better and thus increasing the storage or “sink” of atmospheric carbon dioxide in plants. These of course could be traded to the highest bidder. And, most importantly, these carbon credits would have to be insured. Because if the US had just invested millions of dollars in part of the Bolivian rainforest and it was damaged by a freak wildfire, it would will want compensation.

    Mark Maslin is a climatologist and oceanographer at the Department of Geography, University College London.

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