The biggest global experiment yet conducted to model climate change predictions has found that global temperatures could rise by up to 11°C if emissions of carbon dioxide continue unabated.

Even if the levels of carbon dioxide in the atmosphere increase by less than forecast, temperatures may rise enough to cause problems such as sea level rises and severe weather, according to the research, published today in Nature. Myles Allen of Oxford University, one of the scientists involved, said: "The danger zone is not something we will reach in the middle of this century. We are in it now." Fiona Harvey, London