The drafting of reports by the world's pre-eminent group of climate scientists is an odd process. For months scientists contributing to the Intergovernmental Panel on Climate Change tussle over the evidence. Nothing gets published unless it achieves consensus. This means that the panel's reports are conservative - even timid. It also means that they are as trustworthy as a scientific document can be.

Then, when all is settled among the scientists, the politicians sweep in and seek to excise from the summaries anything that threatens their interests.

The scientists fight back, but they always have to make concessions. The report released on Friday, for example, was shorn of the warning that "North America is expected to experience locally severe economic damage, plus substantial ecosystem, social and cultural disruption from climate change related events".

This is the opposite of the story endlessly repeated in the rightwing press: that the IPCC, in collusion with governments, is conspiring to exaggerate the science. No one explains why governments should seek to amplify their own failures. In the wacky world of the climate conspiracists no explanations are required.

The world's most conservative scientific body has somehow been transformed into a conspiracy of screaming demagogues. This is just one aspect of a story that is endlessly told the wrong way round. In the Sunday Telegraph and the Daily Mail, in columns by Dominic Lawson, Tom Utley and Janet Daley, the allegation is repeated that climate scientists and environmentalists are trying to "shut down debate". Those who say that man-made global warming is not taking place, they claim, are being censored.