Ferenc Miskolczi has analyzed the greenhouse gas effect and come to a different conclusion than the IPCCt. The IPCC modelers use a closed form solution that was done many years ago (I forgot the name of the scientist who did it). For the closed form solution it was assumed that the atmosphere was semi-infinite, though for practical purposes only extends upward about 50 km. Modern computers make it possible to do a numerical solution for a semi-transparent atmosphere of finite extent. One objection I have always had to the IPCC analysis is the assumption in the global circulaion models that relative humidity of the atmosphere remains constant as the atmosphere is warmed by addition of CO2, thus increasing the amount of the greenhouse gas water vapor causing even more heating. This paper indicates that the amount of water vapor in the atmosphere decreases, so that radiative flux remains constant. The paper is a bit complicated.

http://met.hu/idojaras/IDOJARAS_vol111_No1_01.pdf