A computer model of climate run on home PCs in conjunction with the BBC has yielded its first results.
Climateprediction.net uses the power of thousands of ordinary PCs
About 250,000 people downloaded software from climateprediction.net onto their home computers, each running a single simulation of the future.
The results suggest the UK could be about 3C warmer than now in 75 years' time, agreeing with other models.
Full details will be revealed at the weekend in a BBC TV programme presented by Sir David Attenborough.
Members of the scientific team say they have been staggered by the level of interest shown in the project.
"When it started, we said to ourselves that we would be happy if 10,000 people took part," said Nick Faull, climateprediction.net project co-ordinator.
"So to see more than 10 times as many signing up was fantastic," he told the BBC News website
Users were spread across 171 countries. About two-thirds were in the UK; a number of countries including Surinam, Swaziland and Togo were represented by single users.
Initial results apply to UK only; global assessment to follow
By 2020, Britain may be about 1.2C warmer than 1970s base
By 2050, temperatures could be up 2.5C; and in 2080 by 4C
Uncertainty ranges from low of 2C to high of 6C for 2080
Each downloaded a software pack from climateprediction.net which ran when their computer was otherwise idle, with results being fed back to the central server. Each simulation required about three months of computing time on an average PC.
The model itself was developed by the Hadley Centre, part of the UK Meteorological Office, and usually runs on giant supercomputers.
"The main difference is that when you run it in in-house, you can get a wider range of information out because you have much greater resources to store and transfer data," commented Vicky Pope, head of the climate prediction programme at the Met Office.
"It's mainly been done as an educational tool, although the output is useful."
Distributed computing has been used before, notably by the Search for Extra-Terrestrial Intelligence (Seti), where several million people have downloaded software enabling them to analyse data from observations of distant stars for signs of alien life.
The responses from this project have now been analysed by a team bringing together the Open University and the BBC, with funding by the Natural Environment Research Council and with close links to Oxford University.
For 2020, the prediction is that temperatures in Britain will be about 1.2C warmer than in the 1970s, chosen as the baseline for this project.
Temperatures are already almost 1C warmer than in the 1970s, so the rise over the next decade or so will be small if the model is right.
In 2050, they will be about 2.5C higher than the 1970s; while by 2080, the figure could be 4C.
The predictions are not exact; and the further from the present day you look, the greater variability there is, so that by 2080 the rise could be as low as 2C or as high as 6C.
Along with higher temperatures the model predicts greater variability in rainfall, with increased risks of floods and of long dry periods.
"These figures basically support the scientific consensus at the moment," observed Dr Faull
"What makes it especially interesting is that we have included changes to the Sun's output, based on what it has done over the last century; and we find it doesn't make much difference.
"The idea that such changes could influence climate over and above the human influence we don't find very likely."
The model also produced predictions for the climate globally, but these are under wraps at the moment as the team awaits formal publication in a scientific journal.
The state of the global consensus will become clearer in early February when the Intergovernmental Panel on Climate Change (IPCC), the body charged with collating scientific data, publishes the first segment of its fourth assessment report.
David Attenborough presents Climate Change - Britain Under Threat on BBC One at 2000 GMT on Sunday 21 January