Analysis carried out by a distributed network of more than 90,000 PCs has warned that the greenhouse effect and resultant global warming may pose a much more serious threat than scientists previously believed.

The results, which formed the biggest climate monitoring project ever, came from the Climateprediction.net project.

The scheme used a SETI-style model with individuals downloading software that uses the spare capacity of their computers to run global climate simulations.

Published today in the scientific journal Nature, the project paints a grim picture of worldwide temperatures soaring by more than 10 degrees Centigrade if carbon dioxide levels double when compared to pre-industrial times.

In addition to warning of greater maximum temperature rises than previously estimated, the study also pointed to a dramatically greater variance in possible greenhouse-induced increases.

Experts at the Intergovernmental Panel on Climate Change had pegged this possible increase as between two and five degrees Centigrade, but the Climateprediction.net results indicate a possible range of 1.9 to 11.5 degrees.

Project leader David Stainforth, of Oxford University, said that it was not possible to predict when the temperature increases would occur.

However, he pointed out that the doubling of carbon dioxide levels compared with pre-industrial levels, which the simulation had predicted, would occur half way through this century at the current rate of pollution.

Stainforth appealed for computer users to continue helping with the Climateprediction.net project. "There's lots and lots more to do," he told Nature.