Sunday, October 17, 2010

Denying the Catastrophe

Warren Meyer Denying the Catastrophe: The Science of the Climate Skeptic’s Position

Climate skeptics don't necessarily deny that climate is changing. What they deny is to a larger extent that it's all the fault of humans, and most of all, that it's necessarily a catastrophe.

What skeptics deny is the catastrophe, the notion that man’s incremental contributions to CO2 levels will create catastrophic warming and wildly adverse climate changes. To understand the skeptic’s position requires understanding something about the alarmists’ case that is seldom discussed in the press: the theory of catastrophic man-made global warming is actually comprised of two separate, linked theories, of which only the first is frequently discussed in the media.

The first theory is that a doubling of atmospheric CO2 levels (approximately what we might see under the more extreme emission assumptions for the next century) will lead to about a degree Celsius of warming. Though some quibble over the number – it might be a half degree, it might be a degree and a half – most skeptics, alarmists and even the UN’s IPCC are roughly in agreement on this fact.

But one degree due to the all the CO2 emissions we might see over the next century is hardly a catastrophe. The catastrophe, then, comes from the second theory, that the climate is dominated by positive feedbacks (basically acceleration factors) that multiply the warming from CO2 many fold. Thus one degree of warming from the greenhouse gas effect of CO2 might be multiplied to five or eight or even more degrees.

This second theory is the source of most of the predicted warming – not greenhouse gas theory per se but the notion that the Earth’s climate (unlike nearly every other natural system) is dominated by positive feedbacks. This is the main proposition that skeptics doubt, and it is by far the weakest part of the alarmist case. One can argue whether the one degree of warming from CO2 is “settled science” (I think that is a crazy term to apply to any science this young), but the three, five, eight degrees from feedback are not at all settled. In fact, they are not even very well supported.

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