Double, Double, Toil and Trouble
Our lagomorphic friend has a post on new estimates of climate sensitivity from paleoclimate studies. The Earth, for those of us not old enough to remember the actual events (say 600 Myrs) or too old to remember our geology (somewhat less), has had an up and down climate history, temperature-wise. Right now is down, but appears to be going up fast, mainly because there is now more CO2 in the air than there has been for millions of years, and that CO2 is rapidly rising since we keep on burning gigatons of carbon. A very crucial question is how much temperature increase do we get from increasing CO2.
Since the temperature effect of CO2 is nearly logarithmic, it makes sense to define this so-called climate sensitivity as the temperature increase due to a doubling of CO2. The estimates determined from the paleoclimate data, says Herr Rabett, are 2.2 C - 4.8 C. These numbers are pretty big compared to some previous estimates, and would produce dramatic shifts in our climate patterns.