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Michael McCarthy: Why let the facts get in the way of a political opportunity?

Polarisation: there is the reason, in a word, why scepticism about climate change, previously fairly muted, is now enjoying its moment in the sun. Tragically, this issue of atmospheric science, which will affect all our futures, has become politically polarised, and it is now broadly the case that, if we leave aside the scientific community, those who think climate change is a mortal threat are on the liberal-left, whereas those who profess it to be all an exaggeration are on the right.

It is fair to say that it was on the left that the polarisation began. With the collapse of socialism, the future of the climate became a substitute issue for young radicals to take up, people who were rebellious in their tenor, did not dress in suits, might eat lentils and came together in climate camps to attack power stations. More seriously, they began to express their conviction as an ideology, and treat those who dissented as heretics. Thus arose the widely-used phrase "climate deniers", which, with its evocations not only of heresy but also of Holocaust denial, seems to me inappropriate; I have never used it. (It's in the headline of a piece I wrote in 2007, but I didn't write the headline).

To this politicisation from the left, there was eventually an instinctive, hostile response from the right. If these long-haired types were supporting the climate change issue, with their unceasing puritan demands that we stop using our cars and cover the countryside in wind turbines, then those on the right were against it. It was a gut feeling as much as anything, but they were emboldened in their opposition by the fact that the warming itself has been on a plateau for the last decade (although 2009 is likely to be at least the 5th hottest year ever recorded globally, perhaps even the 3rd, and the latest forecast from the Met Office suggests that the warming will resume its progress next year).

Most recently, there has been the affair of the UEA emails – messages from the Climatic Research Unit of the University of East Anglia, which is responsible for constructing one of the main records of historical temperatures. Emails sent by the head of the unit, Professor Phil Jones, appear to show him obstructing the efforts of climate sceptics to obtain information, and most damagingly, to conceal an inconvenient piece of data.

This was the fact that tree ring growth, which is used as a proxy for temperatures in the past, ceases to show the rise in atmospheric temperatures observed in the real world after 1960; in fact it appears to show a decline. In a 1999 email, Professor Jones tells a colleague he is using "the trick" of substituting air temperatures for the inconvenient tree ring data, "to hide the decline." The phrase is chilling; no scientist should be in the business of hiding declines. You can read Professor Jones's explanation for yourself on the UEA website, but in the meantime he has stepped aside from the CRU and there will be an independent inquiry into the matter, as is entirely right.

Yet to imply, as climate sceptics are doing, that because of these emails the whole case for the reality and threat of global warming is somehow invalidated, is complete nonsense. The UEA record is not the only one; there are two others in the US, and they all agree that global average temperatures have increased over the last century and that the warming has been particularly rapid since the 1970s.

The political polarisation of the issue is tragic indeed. We should listen to the scientists; whatever you may read on any climate-sceptic blog, in any climate-sceptic comment piece, there is an overwhelming consensus among scientists who are specialists in atmospheric research that the climate is warming dangerously because of human actions, and that this will continue, with potentially catastrophic consequences, unless we move resolutely to stop it.

This analysis is accepted by every government in the world; on 17 November 2007, at a meeting in Valencia, it was even accepted by the administration of George W Bush, the climate-sceptic supreme, who had spent most of his presidency obstructing the world's efforts to cope with global warming. (If you want to see why the Bush government felt they had to accept it, look at georgewbush-whitehouse.archives.gov/news/releases/2007/11/20071116-21.html)

Hell, it is even accepted by China, one of the most hard-nosed, self-interested nations on the planet. Last week the Chinese announced their first-ever target to cut their carbon emissions. If you're a climate sceptic and you think it's all baloney, what are you saying – that the Chinese are making a Big Mistake? Try telling them that in Beijing.