Generally, the temperature increase due to a doubling of CO2 (280 ppm to 560 ppm) should result in a global average temperature increase of about 1.5 degrees C.
Most of the predictions for future warming lie in the 3 to 11 degree C range, although a few people predict that we could have uncontrolled warming.
Given this difference between CO2 forcing and predicted temperature increases, there is an implication that there is some sort of positive feedback mechanism.
Is it reasonable to assume that there is a positive feedback mechanism at work? Especially in light of the fact that almost all natural systems exhibit negative feedback mechanisms (broad generalization) that tend to dampen the effects of perturbations to a system.
I realize that H2O is often cited as the mechanism, but there is a high degree of uncertainty due to the fact that water vapor can be a driver of cooling AND warming.
Is there historical precedence for assuming that these positive feedbacks exist?
2007-08-29
05:59:59
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9 answers
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asked by
Marc G
4
in
Global Warming