The drizzle of allegations that climate scientists have fudged data, drawn on dodgy sources, withheld information and frozen out dissenters has now become a downpour. Just before the Copenhagen summit there was the damaging leak of documents from the University of East Anglia’s influential Climate Research Unit, revealing less than honest research practices there. In January the UN’s International Panel on Climate Change was forced to retract its claim that the Himalayan glaciers could melt by 2035 after a piece in the New Scientist revealed that it was based on a single interview, given by one glaciologist to the science journalist Fred Pearce in 1999. The IPCC has said it "regrets" the error, but its chairman Rajendra Pachauri at first dismissed questions about the claim as "voodoo science."

This week, in an extensive Guardian investigation of the CRU emails, the same Fred Pearce (who was as surprised as anyone to find his old article taken as gospel, or at least peer-reviewed science, by the IPCC) has reported serious holes in a 1990 research paper by Phil Jones of the CRU and an American colleague, Wei-Chyung Wang. That paper, another key source for the IPCC, claimed to prove that urbanization’s impact on warming is negligible, using data from 84 Chinese weather stations. But Jones and Wang have been unable to say where most of the stations are, and at least 18 are know to have moved during the study–possibly from the outskirts of a sweltering city to the breezy countryside.

So what’s going on? Are these revelations part of an evil conspiracy by the deniers of man-made climate change to discredit climate science? Or do they show (as my learned colleague Alexander Cockburn argues) that anthropogenic warming is just one big snow job?

Science is a way of asking questions, but policymakers demand instant answers. On a subject as politicized as this, it’s not surprising that scientists have been found guilty of hoarding data, smoothing a graph or two, shutting each other’s work out of peer-reviewed journals; the same goes on in far less controversial fields, where what’s at stake is only money and careers. On this topic there’s pressure from both sides–from campaigners and politicians who believe that climate change is the most pressing threat to humankind and from sceptics (or deniers–all these words are loaded) who think it’s a left-wing fantasy, or a threat to the oil industry, or a mere misguided manufactured panic. Many of the CRU emails have a beleaguered tone, as if the scientists clutching secrets to their chests were protecting their work from misuse or unscrupulous attack–as they well may have been. Why, they might ask, do they have to be Caesar’s wife, always and impeccably above suspicion?

Unfortunately that response isn’t nearly good enough. Their sloppy use of data and fudging of evidence has set back efforts to understand climate change and harmed the wider cause of sustainable development. We know that the earth is warming; the evidence convincingly suggests that human activity plays a significant part in this. (Take a look at the blog www.realclimate.orgfor informed, accessible commentary on what we know so far.) But whoever released the CRU documents just before Copenhagen knew what they were doing: nothing makes people angrier than the feeling that they’ve had the wool pulled over their eyes. Every research paper and data set produced by climate scientists or cited by the IPCC is now fair game for the fine-toothed comb, whether it’s wielded honestly or with malicious intent. Nit-picking takes the place of conversation.

Some campaigners have called for a purge at the IPCC and heads may be sent rolling, but I’m not sure that will help, or even if it should. The deeper problem has to do with how science is practiced–not collaboratively but competitively, not following questions but seeking profitable answers–and with its skewed relationship to politics. As Professor Mike Hulme of the University of East Anglia wrote in a Guardian forum,

"The scientific process offers a wonderful method for probing, critical and fearless inquiry into the way the physical world works. But scientific knowledge can never determine policy. Policy emerges through political processes, where interpretations, judgments and compromises are made by individuals and groups of individuals as they weigh uncertain and changing scientific knowledge against normative criteria. It is foolish to state ‘the science demands’ anything. It is people who demand things, not science."

We expect scientists to be arbiters of truth instead of model makers, shrugging off responsibility for deciding what we want. Of course it matters whether warming is caused by human agency; we need to have evidence on which to base rational policies. But we can’t know for sure how climate change will develop; there are too many variables. (For a glimpse of what the science might look like if it wasn’t so politicized, take a look at Wikipedia’s article on the Ice Age.) The experts have to open up the research, be honest about the uncertainties, known knowns and known unknowns, and the rest of us have to stop expecting them to tell us what to do. The argument over global warming stands in for conflicts about many other things: the relationship between the developed and developing worlds, the economic model of infinite growth, extractive versus sustainable use of natural resources, who pollutes and who gets polluted. There is little to lose (except, perhaps, for oil and mining corporations) and everything to gain by switching to sustainable energy, gradually consuming less, leaving the odd tree standing. It is much easier to bicker about botched graphs–important as they are–than it is to confront the politics.