Things are likely to get even hotter

Greenhouse gas emissions could cause global temperatures to rise by up to 11�C, according to first results from the world's largest climate modelling experiment.

The top end of the predictions, which range from two to 11�, is double estimates produced so far and could make the world dramatically different in the future.

"Our experiment shows that increased levels of greenhouse gases could have a much greater impact on climate than previously thought," said David Stainforth, the project's chief scientist, from Oxford University.

Without significant cuts in greenhouse gas emissions, scientists estimate the Earth's temperature and sea level will rise, leading to increased flooding and drastic climate changes.

The temperature range predicted is based on assumptions of carbon dioxide levels double those found before the Industrial Revolution. Scientists estimate these levels will be reached by the middle of this century if greenhouse gas emissions are not reduced.

"This is really just the beginning of the process to try and understand the uncertainty and predictions of climate change," Stainforth added.

From Uruguay to Uzbekistan and Sierra Leone to Singapore, 95 000 people from 150 countries are taking part in the climateprediction.net experiment to explore the possible impact of global warming.

By downloading free software from the site on their personal computers, participants run their own unique version of Britain's Met Office climate model.

While their computer is idle, the programme runs a climate simulation over days or weeks and automatically reports the results to Oxford University and other collaborating institutions around the world.

Together, the volunteers have simulated more than four million model years, donated 8 000 years of computer time and exceeded the processing power of the world's largest supercomputers. The first results of the continuing experiment are reported in the latest edition of the science journal Nature.

"It is entirely possible that even current levels of greenhouse gases, if stable and maintained for a long period of time, could lead to dangerous climate change," Stainforth told reporters.

The Kyoto protocol, the main United Nations scheme to reduce greenhouse gases, aims to cut emissions of carbon dioxide by 5n2 percent below 1990 levels by 2008-12.

"The danger zone is not something we are going to reach in the middle of this century. We are in it now," said Dr Myles Allen of the Met Office.

Climateprediction.net was conceived more than five years ago and launched in 2003. It is funded by Britain's Natural Environment Research Council.