This morning George Will offered another in his series of reassuring columns about the "overstated" threat of climate change.  Today's version:

"When New York Times columnist Tom Friedman called upon 'young Americans' to 'get a million people on the Washington Mall calling for a price on carbon,' another columnist, Mark Steyn, responded: 'If you're 29, there has been no global warming for your entire adult life. If you're graduating high school, there has been no global warming since you entered first grade.'

"Which could explain why the Mall does not reverberate with youthful clamors about carbon. And why, regarding climate change, the U.S. government, rushing to impose unilateral cap-and-trade burdens on the sagging U.S. economy, looks increasingly like someone who bought a closetful of platform shoes and bell-bottom slacks just as disco was dying."

Will presented the lack of youthful clamor as a sign of wholesome common sense. If you would like another way to think about the evidence, this one provided not by a columnist but by a physicist at UC Berkeley who has won a MacArthur grant, I recommend Richard A. Muller's book Physics for Future Presidents. I happened to read most of it on a long plane flight yesterday, so I was all set for Will's column today. So you can be ready before his next one appears, I recommend ordering the book now.

Muller is not at all in the most-alarmist group of climate scientists; indeed, he spends a lot of time explaining why he thinks Al Gore's Inconvenient Truth exaggerated the threat in several ways. You can see the beginning of his dissection of Gore's famous "hockey stick" chart of rising temperatures, which begins on page 292 of Muller's book, through a Google book-search excerpt here. (The hockey stick, below)

HockeyStick.jpg

Muller says that the evidence behind the hockey-stick chart is wrong. (Read it yourself to see why.) "In fact, much of what the public 'knows' about global warming is based on distortion, exaggeration, or cherry picking," he says, adding:

"An example of distortion is the melting of the Antarctic ice -- something that actually contradicts the global warming model but is presented as if it verifies them. Exaggeration includes the attribution of Hurricane Katrina to global warming, even though there is no scientific evidence that they are related.  Cherry picking is the process of selecting data that verify the global-warming hypothesis but ignoring data that contradict it."

The real purpose of his book is to set out as clearly as possible the way scientists approach the inevitably-conflicting evidence on big public policy issues like climate change (or the real risks of terrorism, or dealing with nuclear waste). Before the Iraq war, it would have been useful for intelligence officials to set out the way they balance their version of inevitably-conflicting and always-incomplete facts. Muller sets out the way climate scientists weigh the evidence pro and con concerning climate change and the probabilities for each explanation.

By the end of the process he has forcefully re-established the principle that real scientists view propositions as most convincing when all the doubts, caveats, and contrary bits of evidence are admitted -- whereas politicians and the public want to hear an all-or-nothing verdict with no hems or haws. Consistent with this approach, it is all the more powerful when Muller concludes that there really are reasons to worry about man-made climate change. He also provides guidelines about sensible and fanciful ways to deal with the problem. I am not equipped to judge this argument on purely scientific grounds; but the book is addressed to lay readers and is convincing in what it says about the process of scientific reasoning. If this latest George Will opus serves to drive readers to Muller's book, it will have done some good.