According to a recent rash of stories in the media, the "climate sensitivity" – the extent to which temperatures respond to more carbon dioxide in the atmosphere – is lower than expected, and thus that the world won't get as hot as predicted. One story, in The Economist, based on leaked information from a draft of the next assessment by the Intergovernmental Panel on Climate Change, claims the IPCC will revise its sensitivity estimate downwards when they release their official report this September.

The sceptics have mounted a concerted campaign to persuade journalists and politicians that climate scientists now think that climate sensitivity is lower, says Bob Ward of the Grantham Research Institute on Climate Change and the Environment, London. But is there any truth to the claims?