Matt Ridley, a prolific author (among many other professional accomplishments) recently name-checked by Bill Clinton as one of the “smartest, most penetrative thinkers” remains one of the highest profile skeptics toward the likelihood of catastrophic anthropogenic global warming. Last week he delivered the 2011 Angus Millar Lecture at the Royal Society of Arts in Edinburgh. The title of his talk was “Scientific Heresy,” and it detailed extensively why he remains skeptical on this issue. You can read the entire text of the talk here. A PDF with accompanying graphs and charts is here.

Here are a few excerpts, though the speech in its entirety should not be missed if you follow this debate:

Using these six lessons, I am now going to plunge into an issue on which almost all the experts are not only confident they can predict the future, but absolutely certain their opponents are pseudoscientists. It is an issue on which I am now a heretic. I think the establishment view is infested with pseudoscience. The issue is climate change.

Now before you all rush for the exits, and I know it is traditional to walk out on speakers who do not toe the line on climate at the RSA – I saw it happen to Bjorn Lomborg last year when he gave the Prince Philip lecture – let me be quite clear. I am not a “denier”. I fully accept that carbon dioxide is a greenhouse gas, the climate has been warming and that man is very likely to be at least partly responsible. When a study was published recently saying that 98% of scientists “believe” in global warming, I looked at the questions they had been asked and realized I was in the 98%, too, by that definition, though I never use the word “believe” about myself. Likewise the recent study from Berkeley, which concluded that the land surface of the continents has indeed been warming at about the rate people thought, changed nothing.

So what’s the problem? The problem is that you can accept all the basic tenets of greenhouse physics and still conclude that the threat of a dangerously large warming is so improbable as to be negligible, while the threat of real harm from climate-mitigation policies is already so high as to be worrying, that the cure is proving far worse than the disease is ever likely to be. Or as I put it once, we may be putting a tourniquet round our necks to stop a nosebleed.

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I’ve looked and looked but I cannot find one piece of data – as opposed to a model – that shows either unprecedented change or change is that is anywhere close to causing real harm.

No doubt, there will be plenty of people thinking “what about x?” Well, if you have an X that persuades you that rapid and dangerous climate change is on the way, tell me about it. When I asked a senior government scientist this question, he replied with the Paleocene-Eocene Thermal Maximum. That is to say, a poorly understood hot episode, 55 million years ago, of uncertain duration, uncertain magnitude and uncertain cause.

Meanwhile, I see confirmation bias everywhere in the climate debate. Hurricane Katrina, Mount Kilimanjaro, the extinction of golden toads – all cited wrongly as evidence of climate change. A snowy December, the BBC lectures us, is “just weather”; a flood in Pakistan or a drought in Texas is “the sort of weather we can expect more of”. A theory so flexible it can rationalize any outcome is a pseudoscientific theory.

To see confirmation bias in action, you only have to read the climategate emails, documents that have undermined my faith in this country’s scientific institutions. It is bad enough that the emails unambiguously showed scientists plotting to cherry-pick data, subvert peer review, bully editors and evade freedom of information requests. What’s worse, to a science groupie like me, is that so much of the rest of the scientific community seemed OK with that. They essentially shrugged their shoulders and said, yeh, big deal, boys will be boys.

Nor is there even any theoretical support for a dangerous future. The central issue is “sensitivity”: the amount of warming that you can expect from a doubling of carbon dioxide levels. On this, there is something close to consensus – at first. It is 1.2 degrees centigrade. Here’s* how the IPCC put it in its latest report.

“In the idealised situation that the climate response to a doubling of atmospheric CO2 consisted of a uniform temperature change only, with no feedbacks operating…the global warming from GCMs would be around 1.2°C.” Paragraph 8.6.2.3.

Now the paragraph goes on to argue that large, net positive feedbacks, mostly from water vapour, are likely to amplify this. But whereas there is good consensus about the 1.2 C, there is absolutely no consensus about the net positive feedback, as the IPCC also admits. Water vapour forms clouds and whether clouds in practice amplify or dampen any greenhouse warming remains in doubt.

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In conclusion, I’ve spent a lot of time on climate, but it could have been dietary fat, or nature and nurture. My argument is that like religion, science as an institution is and always has been plagued by the temptations of confirmation bias. With alarming ease it morphs into pseudoscience even – perhaps especially – in the hands of elite experts and especially when predicting the future and when there’s lavish funding at stake. It needs heretics.

Thank you very much for listening.

The Competitive Enterprise Institute held a joint event with Reason magazine last year for Matt Ridley’s latest book: The Rational Optimist.