The mess at Copenhagen is one reason. So much effort went into the event, with so little result. The recession is another. However much bosses may care about the planet, they usually mind more about their bottom line, and when times are hard they are unwilling to incur new costs. The bilious argument over American health care has not helped: this is not a good time for any bill that needs bipartisan support. Even the northern hemisphere's cold winter has hurt. When two feet of snow lies on the ground, the threat from warming seems far off. But climate science is also responsible. A series of controversies over the past year have provided heavy ammunition to those who doubt the seriousness of the problem.

Three questions arise from this. How bad is the science? Should policy be changed? And what can be done to ensure such confusion does not happen again? Behind all three lies a common story. The problem lies not with the science itself, but with the way the science has been used by politicians to imply certainty when, as often with science, no certainty exists.

What went wrong and what did not

When governments started thinking seriously about climate change they took the sensible step of establishing, in 1989, the Intergovernmental Panel on Climate Change. It was designed to get scientists to work out what was happening to the climate, and to get governments to sign off on the scientists' conclusions. It has done the job of basic science pretty well. There have been occasional complaints both that it has overstated the extent of the problem, and that it has understated it. Its reports trawl through all recent climate science. The wide range of the outcomes it predicts — from a mildly warming global temperature increase of 1.1°C by the end of the century to a hellish 6.4°C — illustrate the uncertainties it is dealing with.