I was looking at a Hansen article from the 1980s, and think I am starting to understand where his bloated theories about climate sensitivity come from.
Look at his calculations for radiative and convective equilibrium temperature on Venus. The convective equilibrium numbers make sense – it is a simple calculation of lapse rate times height of the atmosphere – and yields the correct value for the surface temperature. As the atmosphere convects, falling air compresses and heats – while rising air expands and cools. He shows the lapse rate of Venus (7) not much different from Earth (5.5.) (This in itself should be enough information to convince someone that the idea of a runaway greenhouse effect is nonsensical.)
But the problem lies with the radiative equilibrium calculation (1.) He starts with a WAG (Wild Ass Guess) of atmospheric infrared opacity – 100 times greater than Earth.
The statement below is unpalatable, because it assumes no convection.
A quantitative estimate of the greenhouse effect can be obtained under the assumption that only radiation contributes significantly to vertical energy transfer.
Then he assumes that he can calculate the surface temperature based on the total atmospheric opacity? That is ridiculous. The atmosphere of Venus is very thick and is covered with a layer of thick opaque clouds. The total opacity tells us little or nothing about the temperature profile or surface temperature, particularly since he assumes that Venus atmosphere is not convecting – which obviously it is.
Equation 2 is adequate and correct. His usage of equation 1 looks useless to me and apparently is the basis of his theories about climate sensitivity.