THE Earth could be even more sensitive to global warming than we imagined. If carbon dioxide levels in the atmosphere double, as they are widely expected to do, the planet鈥檚 temperature could rise by a huge 11.5 掳C, according to early results from a project that uses home PCs to test climate models.
The result is surprising because it is far outside the 1.4 to 4.5 掳C range predicted by the Intergovernmental Panel on Climate Change. But the IPCC鈥檚 estimate is based on just a handful of different computer models of the Earth鈥檚 climate (see New 杏吧原创, 24 July 2004, p 44). 鈥淲e have anecdotal evidence that people tend to tune their models to be similar to other people鈥檚,鈥� says David Stainforth of the University of Oxford. But this may also have the effect of limiting the predictions the models make.
So Stainforth and his colleagues launched the website climateprediction.net to see what would happen when models were not tuned in this way. More than 95,000 volunteers have downloaded software from climateprediction.net, and have tested more than 2000 different climate models. The models are first tested to ensure that they simulate the past climate accurately, then checked to see what they predict for the future. The result is a forecast temperature rise ranging from 1.9 to 11.5 掳C (Nature, vol 433, p 403).
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