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What is Endangered: Climate or Freedom? And Just How Sensitive is the Climate Anyway? |
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Written by Ronald Bailey, Reason magazine
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Wednesday, 05 March 2008 |
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Page 1 of 4 Let's start with some possible news from Heartland Institute's International Climate Change Conference.
In the context of man-made global warming, climate sensitivity asks how
much temperatures increase if one adds a specified amount of a
greenhouse gas. In general, most climatologists accept the proposition,
all things being equal, that if one doubles carbon dioxide in the
atmosphere the average temperature will go up by +1 degree centigrade.
But all things are not equal. In climate models, additional heat from
carbon dioxide boosts atmospheric water vapor which in turn acts as a
greenhouse gas. All models are dominated by this positive feedback
loop. As a consequence, the U.N.'s Intergovernmental Panel on Climate
Change (IPCC) estimated in its Fourth Assessment Report (4AR) last year that it "is likely to be in the range 2 to 4.5°C with a best estimate of about 3°C, and is very unlikely to
be less than 1.5°C." In other words, doubling carbon dioxide in the
atmosphere is likely to warm the planet by between 2 degrees and 4.5
degrees centigrade.
So how do we find out how sensitive
climate is to CO2? During his luncheon keynote, University of Alabama
climatologist Roy Spencer described how two of his new studies are
attempting to answer that question. In 2001, Massachusetts Institute of
Technology climatologist Richard Lindzen hypothesized that there might
be what he called an "adaptive infrared iris" over the tropics through which tropical storms dissipate excess heat. But other researchers looked and found no strong evidence for such a mechanism.
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