CLIMATE-change legislation, dormant for six months, is showing signs of life again in Washington, DC. This week senators and industrial groups have been discussing a compromise bill to introduce mandatory controls on carbon (see article). Yet although green activists around the world have been waiting for 20 years for American action, nobody is cheering. Even if discussion ever turns into legislation, it will be a pale shadow of what was once hoped for.

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.

But the ambiguities of science sit uncomfortably with the demands of politics. Politicians, and the voters who elect them, are more comfortable with certainty. So “six months to save the planet” is more likely to garner support than “there is a high probability—though not by any means a certainty—that serious climate change could damage the biosphere, depending on levels of economic growth, population growth and innovation.” Politics, like journalism, tends to simplify and exaggerate. Hence the advertisements that the British government has been running, using nursery rhymes: “Jack and Jill went up the hill to fetch a pail of water. There was none as extreme weather due to climate change had caused a drought.”

Such an approach may, in the short term, have encouraged some voters to support measures to combat climate change. But implying that Britain's children face some sort of Saharan future is wrong, and dangerous. This week Britain's Advertising Standards Authority slapped the government for its infantile advertisements. And there has been worse.

In November, shortly before the Copenhagen climate summit, a stash of e-mails from and to various researchers at the Climatic Research Unit of the University of East Anglia somehow found its way onto the web. They revealed an unwillingness to share data which broke the spirit, if not the letter, of Britain's Freedom of Information act, an aggressive attitude to the peer review of papers by opponents and an apparent willingness to hedge science in the face of politics. Around the same time it emerged that the most recent IPCC report had claimed that the Himalayan glaciers were going to disappear by 2035, instead of 2350. The panel's initial unwillingness to address this mistake, and the discovery of further problems with its work, raised troubling questions about its procedures.

How bad is this? Sceptics point out that each mistake has tended to exaggerate the extent of climate change. The notion that the scientific establishment has suppressed evidence to the contrary has provided plenty of non-expert politicians with an excuse not to spend money reducing carbon. So the scientists' shameful mistakes have certainly changed perceptions. They have not, however, changed the science itself.

As our briefing explains in detail, most research supports the idea that warming is man-made. Sources of doubt that have seemed plausible in the past, such as a mismatch between temperatures measured by satellites and temperatures measured at the surface, and doubts about the additional warming that can be put down to water vapour, have been in large part resolved, though more work is needed. If records of temperature across the past 1,000 years are not reliable, it matters little to the overall story. If there are problems with the warming as measured by weather stations on land, there are also more reliable data from ships and satellites.

Insuring against catastrophe

Plenty of uncertainty remains; but that argues for, not against, action. If it were known that global warming would be limited to 2°C, the world might decide to live with that. But the range of possible outcomes is huge, with catastrophe one possibility, and the costs of averting climate change are comparatively small. Just as a householder pays a small premium to protect himself against disaster, the world should do the same.

This newspaper sees no reason to alter its views on that. Where there is plainly an urgent need for change is the way in which governments use science to make their case. The IPCC has suffered from the perception that it is a tool of politicians. The greater the distance that can be created between it and them, the better. And rather than feeding voters infantile advertisements peddling childish certainties, politicians should treat voters like grown-ups. With climate change you do not need to invent things; the truth, even with all those uncertainties and caveats, is scary enough.



