Previous posts have shown that the figure for climate sensitivity (CS - the degree by which global climate varies in response to a given change in its heat balance) is centered around 3*C.
The anti-AGW lobby cannot live with this figure: their position is predicated firmly on a low CS. If they cannot substantiate it, their claim to have a scientific position is empty and void.
A sceptic tweeter points me to Fred Singer's NIPCC report. Chapter 2 - Feedback Factors and Radiative Forcing. Exactly what I need.
Singer claims that the IPCC has overestimated CS by an order of magnitude:
That is, he claims that CS for doubling CO2 will lie somewhere between 0.15 and 0.45*C.
Good. At least we have a figure. Unfortunately I cannot find anywhere in the text where he works out this figure. Maybe he has done it somewhere. On the other hand, Singer has a record of making unsubstantiated claims.
However, going with his figure of 0.15-0.45, the first problem is that if climate sensitivity were to be that small, climate would not vary at all. Any warming effect would produce strong negative feedbacks that would
oppose the warming effect, and the planet would not warm significantly. So the low CS value of the sceptics is refuted by the very fact of climate change through natural variation so beloved by the sceptics.
In other words, CS has to be greater than 1.5*C or so, simply because the planet's temperature goes up and down.
I'm tempted to leave it there, like that, and see if any sceptics come over and poke me into looking further at the NIPCC report.
Surely refuting the sceptics' case cannot be this simple?