Nicholas Lewis (who with Jeff Id and Ryan O’Donnell rebutted Steig et al and the flawed Antarctica surface temperature analysis) writes in with a note about a post on Climate, Etc. (Judith Curry’s blog) related to the IPCC AR4 and their estimate of climate sensitivity.
The IPCC Third Assessment Report (TAR), said it was “likely to be in the range of 1.5 to 4.5°C” (from . “Technical Summary: F.3 Projections of Future Changes in Temperature”
More recent work continues to support a best-guess value around 3°C (from “The equilibrium sensitivity of the Earth’s temperature to radiation changes”)
There’s been a lot of talk about this as of late, and the number that I keep hearing repeated again and again is in the range of 1.1 to 1.4°C per doubling of CO2. Recently at ICCC6 in Washington, Dr. Roy Spencer suggested in his debate with Dr. Scott Denning that the value seems to be 1.3°C per 2xCO2 based on his analysis of temperature observations.
Nicholas Lewis has found what may be an error with IPCC’s calculation of climate sensitivity and writes: (WUWT)