For years, climate-change activists such as myself have been fond of asserting that "the time for debate on global warming is over - and the time for action is now". But the debate hasn't ended, despite our attempts to suggest otherwise: it rages on. And its contin uation raises fundamental questions, not just about the effect that humankind might have on the atmosphere, but about the nature of science, reason and democracy itself.
Here in Britain, the ever-controversial Channel 4 weighed in on 8 March with a film by Martin Durkin, provocatively titled The Great Global Warming Swindle. In New York, just over a week later, National Public Radio organised an Oxford Union-style spat between the climate scientists Gavin Schmidt, Richard Somerville and Brenda Ekwurzel, and the climate sceptics Richard Lindzen (also a scientist), the novelist Michael Crichton and the retired geographer Philip Stott. The transcript makes depressing reading: according to the voting roster, the net result was that there were fewer people convinced about global warming at the end of the debate than there were at the beginning.
Liberals such as myself tend to assume that debates are always a good thing: that if enough facts can be marshalled in support of a particular case, then the truth will out. It is this assumption that drives us to write books and talk on the radio about important issues such as global warming. "If everyone knew what I know," is the underlying mental reasoning, "everyone would think like me." Wrong. Competing world-views will determine different stances on an issue, particularly where "facts" are disputed. Moreover, argu ments about science may simply be obscuring debates about something far more fundamental.
As Gavin Schmidt pointed out in the New York debate: "Creationists have argued that the eye is too complex to have evolved - not because they care about the evolution of eyes, but because they see the implications of evolution as somehow damaging to their world-view." And he concludes, rightly: "If you demonstrate the evolution of eyes, their world-view won't change. They'll just move on to something else."
In Channel 4's case, Durkin has amply de-monstrated his antipathy to environmentalism in previous programmes, and most of his interviewees have similar track records. Despite the graphs, none of this has much to do with greenhouse gases: what is happening is that a scientific debate has become politicised - or perhaps a political debate has become scientised.
So does this mean that objective truth - or at least its closest approximation - is impossible to discover via the scientific method? I would argue not, though such relativism is obviously appealing to the postmodernists who run Channel 4. Indeed, without core scientific principles - the possibility of falsification, the repeatability of experiments, the open sharing of data, and so on - we are left with little more than faith and assertion. Indeed, scientists such as Schmidt do strive to be values-free, objective and rational, and base their claim to credibility on this: "We are scientists, we talk about science, and we're not going to start getting into questions of personal morality and wider political agendas," he writes on the RealClimate blog.
But, for non-scientists such as myself, that claim would be more than a little disingenuous. While my latest book, Six Degrees, is a review of the science, and is in my opinion an honest assessment of the state of the expert literature, I cannot deny that my concern about global warming is rooted in a world-view that sees a planet overexploited by humans, and that this world-view long predates any knowledge I now have about climatology.
I should also admit that on occasion I have been quite happy to resort to the kind of tactics used by today's climate sceptics - when battling the introduction of genetically engineered crops a few years ago, for example, I constantly asserted that science had been distorted by financial interests. Today, when I hear the same arguments used to undermine the credibility of climate scientists, I explode with righteous fury. (In my defence, the two things aren't directly comparable: GM was the introduction of a new technology with inherent risks; while climate science seeks to identify the risks inherent in modifying the atmosphere's chemistry as a result of burning fossil fuels.)
But the last word should go to a Swiss correspondent on the RealClimate site, who pointed out why such science-about-values debates - such as that between climate scientists and sceptics, or worse, environmentalists and sceptics - are essentially pointless.
"In a field where uncertainties are everywhere around," writes Urs Neu, "it is much easier to confuse people than to convince them." So unfortunately my liberal assumption is probably wrong: the truth will not necessarily out, and debates are not always beneficial to those who seek it. In a democracy, appeals to public ignorance may be just as successful as appeals to public wisdom.