Global warming is 'twice as bad as previously thought'

Global warming might be twice as catastrophic as previously thought, flooding settlements on the British coast and turning the interior into an unrecognisable tropical landscape, the world's biggest study of climate change shows.

Global warming might be twice as catastrophic as previously thought, flooding settlements on the British coast and turning the interior into an unrecognisable tropical landscape, the world's biggest study of climate change shows.

Researchers from some of Britain's leading universities used computer modelling to predict that under the "worst-case" scenario, London would be under water and winters banished to history as average temperatures in the UK soar up to 20C higher than at present.

Globally, average temperatures could reach 11C greater than today, double the rise predicted by the Intergovernmental Panel on Climate Change, the international body set up to investigate global warming. Such high temperatures would melt most of the polar icecaps and mountain glaciers, raising sea levels by more than 20ft. A report this week in The Independent predicted a 2C temperature rise would lead to irreversible changes in the climate.

The new study, in the journal Nature, was done using the spare computing time of 95,000 people from 150 countries who downloaded from the internet the global climate model of the Met Office's Hadley Centre for Climate Prediction and Research. The program, run as a screensaver, simulated what would happen if carbon dioxide levels in the atmosphere were double those of the 18th century, before the Industrial Revolution, the situation predicted by the middle of this century.

David Stainforth of Oxford University, the chief scientist of the latest study, said processing the results showed the Earth's climate is far more sensitive to increases in man-made greenhouse gases than previously realised. The findings indicate a doubling of carbon dioxide from the pre-industrial level of 280 parts per million would increase global average temperatures by between 2C and 11C.

Mr Stainforth said: "An 11C-warmed world would be a dramatically different world... There would be large areas at higher latitudes that could be up to 20C warmer than today. The UK would be at the high end of these changes. It is possible that even present levels of greenhouse gases maintained for long periods may lead to dangerous climate change... When you start to look at these temperatures, I get very worried indeed."

Attempts to control global warming, based on the Kyoto treaty, concentrated on stabilising the emissions of greenhouse gases at 1990 levels, but the scientists warned that this might not be enough. Mr Stainforth added: "We need to accept that while greenhouse gas levels can increase we need to limit them, level them off then bring them back down again."

Professor Bob Spicer, of the Open University, said average global temperature rises of 11C are unprecedented in the long geological record of the Earth. "If we go back to the Cretaceous, which is 100 million years ago, the best estimates of the global mean temperature was about 6C higher than present," Professor Spicer said. "So 11C is quite substantial and if this is right we would be going into a realm that we really don't have much evidence for even in the rock [geological] record."

Myles Allen, of Oxford University, said: "The danger zone is not something we're going to reach in the middle of the century; we're in it now." Each of the hottest 15 years on record have been since 1980.