FYI, I have studied the IPCC AR's in great detail and this is why I know for a fact that they are wrong. The mechanism established by the IPCC to determine the sensitivity is seriously flawed. We can start with the ambiguity in defining forcing, where 1 W/m^2 of post albedo incremental solar input power is considered 1 W/m^2 of forcing, while a 1 W/m^2 instantaneous increase in surface emissions absorbed by the atmosphere is also considered forcing. The later assumes that all power absorbed by the atmosphere is returned to the surface to warm it, as the an entire W/m^2 of solar forcing does, while the data clearly tells us that about half of atmospheric absorption by GHG's and clouds ultimately escapes into space and has no warming effect on the surface. Otherwise, clouds would not emit any power into space.
At the very least, you must concede that the sensitivity of an ideal black/gray body is given by the slope of the SB relationship, which is quantified as 1/(4*e*o*T^3), where e is the emissivity (.62 for a gray body representation of Earth and 1.0 for an ideal black body), o is the SB constant and T is the temperature of that body. To achieve a sensitivity of 0.8C per W/m^2, e must be only 0.23. Given planet emissions of 239 W/m^2, this requires the surface to be emitting over 1039 W/m^2 of Planck radiation which corresponds to a temperature close to the boiling point of water. Obviously, this is not the case, so the only other possibility is that the T^3 dependence of sensitivity on T must be about T^3.23 since e and o are otherwise known.
Please answer this question:
What physics do you propose can change the dependency of the sensitivity on temperature from T^3 to T^3.23, bearing in mind that this also requires that the radiant emissions of the surface go as T^4.23, rather than the T^4 otherwise dictated by the laws of physics? Please be specific and cite the precise physical law or laws. Arguments to authority are insufficient to establish this much deviation from first principles physics which is basically all you have done in #68 and others.