onsdag 8 september 2010
Climate Sensitivity 0.5 C
Frank Lanser has a guest post on WUWT arguing that climate sensitivity (global warming from doubled CO2 concentration) is at most 0.5 C. I agree and have come to the same conclusion, using similar reasoning: The simple argument goes as follows:
Out of the present total warming effect of the atmosphere of 33 C, at most 15 % may be due to CO2, say at most 5 C (probably less). Now, the warming effect of CO2 could well be logarithmic in its dependence on concentration, and thus the effect declines with each doubling. With 10 doublings to reach the present level, each doubling would correspond less than 0.5 C, as a first crude estimate of total climate sensitivity including feedbacks.
Another crude estimate is to say that doubled CO2 may give a "radiative forcing" of 1% of
total incoming radiation with a corresponding 1% change of a total temperature drop of 33 C, that is 0.3 C, according to Fourier's Law, including feedbacks.
Yet another crude estimate is to say that a "radiative forcing" of 2 W/m2 would correspond to a 2% increase of the 120 W/m2 delivered from the Earth surface by convection/latent heat
under a temperature drop of 30 C, with a corresponding 2% increase of the temperature drop of 0.6 C , including feedbacks.
This is to be compared with IPCC's first crude estimate = 2 - 4.5 C, a factor 5 - 10 bigger. Climate alarmism is solely based on this factor 5 - 10, which lacks scientific rationale.