The Financial Times, May 30 2008

From storms, floods and drought to the spread of disease and famine - the projected results of global warming make for grim reading. Few regions of the world will remain untouched by the phenomenon and human habitation will be affected radically.

The science of climate change can trace its roots back to the 19th century, but the body of research has multiplied in recent years as evidence of global warming has grown. Early chemists theorised that carbon dioxide trapped infrared heat, and that rising concentrations of the gas would cause the world's surface to warm. But it took many years for the necessary scientific instrumentation to catch up, and for a warming "signal" to become clear to observers through the vagaries and variations of the earth's climate. Even by the 1990s, it was hard to say whether the warming was simply a natural phenomenon.

Last year, the IPCC published the most comprehensive study of climate change science, and for the first time scientists swept away the last remaining doubts that climate change was happening, and that human actions were playing an important role in that process. The Intergovernmental Panel on Climate Change concluded that there was a 90 per cent certainty that the climate was becoming warmer and that the actions of people - in chopping down forests and burning fossil fuels - were a large part of the problem.

Ban Ki-moon, United Nations secretary-general, hailed the findings and said they should prompt radical changes in policy: "The world's scientists have spoken clearly and with one voice. I expect world policymakers to do the same."

The central findings of last year's report, which warned starkly of the probable disastrous impacts of climate change if greenhouse gas emissions

continue unchecked, will form the scientific basis for the next 18 months of negotiations on whether there is a future for a global treaty on emissions, and thus a basis of international climate change policy for decades to come.

The IPCC was set up in 1988 by the World Meteorological Organisation and the UN Environment Programme, after years of rising concerns over the possibility of global warming. Its remit was not to carry out research but to collate and summarise the latest peer-reviewed science from a wide variety of sources and to publish a report on its findings.

When its first report was published in 1990, the conclusions were necessarily tentative. The scientists predicted a rise in global average temperatures of about 0.3°C per decade in the 21st century, which would still be greater than any seen in the past 10,000 years. But they noted that such warming as had been observed was not beyond the bounds of natural variability of the climate, and that more research was needed to establish its probable cause.

Nevertheless, their warnings were enough to prompt the Earth Summit held in Rio de Janeiro in 1992, at which the world's nations - including the US, under the first President George Bush - signed up to the UN Framework Convention on Climate Change. This committed governments to the "stabilisation of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system".

The treaty did not set out how this would be achieved, or in what time frame it should be considered. These questions had to wait for the 1997 Kyoto Protocol - an addition to the Framework Convention - which required rich countries to cut their emissions by an average of 5 per cent compared with 1990 levels, by 2012.

While the US refused to ratify this treaty, the past 10 years have seen a gradual shift in thinking, and Washington, under George W. Bush, US president, has committed itself to the "roadmap" of negotiations on a successor treaty that was agreed last December in Bali.

Since its first report in 1990, the IPCC's findings have become firmer as a greater amount of scientific muscle has been brought to bear on examining climate change and new techniques have been developed.

For instance, it is now commonplace to base deductions on drilling deep into the polar ice to produce long "ice cores". These date back hundreds of thousands of years, and by examining the bubbles of gas trapped within them, scientists can make accurate guesses as to what the earth's ancient climate was like. Similar deductions can be made by examining ancient trees, whose rings hold within them data on past climate.

The IPCC's painstaking methodology means it is slow-moving, but its reports carry great credibility among scientists. Each IPCC report - last year's was the fourth - takes between four and six years to draw up. Although the process is long, this enables the panel to draw on the widest possible range of research.

The research behind last year's much-lauded fourth report involved more than 2,500 scientists. The information was edited by 174 lead authors and 222 contributing authors. The amount of ground covered was also vast - for example, in order to come to the conclusion that spring was occurring earlier across the world, the editors considered 29,000 sets of observational data. The "summaries for policymakers", containing the key findings, were agreed by all the participating governments, including the US, the European Union and leading developing nations such as China and India.

But the IPCC has also attracted its fair share of controversy. The organisation has been attacked by critics from both sides, some accusing it of adopting a political agenda far beyond its mandated role of assessing climate change, others saying it is too conservative.

Lord Lawson, the former UK chancellor of the exchequer who has written a book casting doubt on climate change science, has called for reform of the IPCC, arguing its processes are flawed and open to political manipulation. The same position is taken by many on the right in the US, who also accuse Rajendra Pachauri, the IPCC's chairman, of taking a political stand.

Mr Pachauri's response is to point to the methods used to produce the IPCC's report. "Everything [included in the report] is by consensus, so the implication is that it has the stamp of acceptance by all governments in the world," he says.

From the other side, critics have argued that the IPCC processes are too bureaucratic to take account of the latest science in each report. They say this leads to an unacceptable time lag of several years before new research is incorporated into IPCC reports.

Some also protest that the processes are open to political manipulation from large countries such as the US and China, who have been accused of seeking to water down some of the more striking conclusions. Some scientists have even threatened to withdraw their support on the basis that their findings, showing strong risks to the climate, have been underplayed.

Whatver its merits and shortcomings, the IPCC is the leading international body that can claim to speak with authority on climate change science. Last year's report was the biggest the body has produced. It was published in three parts: the first dealt with updates in core climate change science, laying out what the likely changes in global temperatures and climate would be in the next century.

The second surveyed the likely impacts these changes would have, for instance, on the availability of water and food, and on human migration.

The third examined ways of avoiding these effects and the likely costs of cutting greenhouse gas emissions. An additional publication, summarising the chapters, was created for the negotiators meeting at Bali.

The central finding of the first section of the report was that global average temperatures were likely to rise about 3°C by 2100. This figure pinpointed the "best estimate" of a range from 2°C to 4.5°C, though some outlying estimates predicted the world could warm by more than 6°C, which would occur if the rainforests died. However given that scientists estimate global average temperatures during the last ice age were only about 5°C-6°C colder than at present, this still represents a remarkable shift.

Such warming would bring with it water shortages, heatwaves, storms and floods. Diseases now confined to tropical regions would spread, and agriculture would become impossible in some areas that are already arid. Millions of people would be put at risk of flooding from sea level rises.

Some regions could see benefits - areas of Europe, North America and Russia that are currently barren or offer marginal agricultural returns could be cultivated with a range of crops. Farmers in Canada and northern Europe, for instance, could look forward to crop yield increases of between 5 per cent and 15 per cent. But these gains might be offset by an increase in extreme weather - more storms, more droughts, shifting rainfall patterns.

"It's exactly what you don't want," says Martin Parry, co-chairman of the IPCC. "Where it's already moist you don't want more [water]. And it is decreased in latitudes [that are dry]."

Largely missing from the IPPC's report was a discussion of the potential of "feedback loops", by which the effects of climate change intensify warming, and "tipping points", or natural thresholds of environmental change, beyond which it is difficult for natural systems to adjust (see page 22).

One feedback loop that some scientists think is already in operation is the effect of the melting polar ice caps on the earth's albedo (its ability to reflect the rays of the sun). Ice reflects the sun's rays, meaning a great deal of their heating effect is lost. But as the ice caps melt under a warming atmosphere, they give way to water, which is dark and thus absorbs more heat. This in turn leads to more warming and a rapid acceleration of the melting.

One of the tipping points that scientists have begun to investigate is the melting of permafrost. In regions such as Siberia, large tracts of frozen bog lie under the frozen ice, but as this begins to thaw, it releases methane - a greenhouse gas more than 20 times as powerful as carbon dioxide. This could trigger a similar feedback loop, which could lead to runaway global warming.

Studying past temperatures shows that shifts in the climate can occur quite suddenly, which some scientists attribute to the existence of these tipping points and feedback loops.

Scientists are only beginning to gauge the possible impacts of such phenomena. It is too early to say what effect they will have on climate change over the coming decades - or whether some of the tipping points have already been reached.

Source: http://www.ft.com/cms/s/0/38ab6542-2ca0-11dd-88c6-000077b07658,dwp_uuid=4cd2f1a2-28d6-11dd-96ce-000077b07658.html?nclick_check=1