The continuing large traffic on previous threads on the topic of radiative transfer (and increasingly on threads with unrelated topics) has demonstrated the need for a new thread. Here are some posts to start the new discussion over here:
From Arfur Bryant:
In answer to your question; yes, I suppose I do have a problem believing the radiative transfer models as it appears to me that they are based on an assumption. Even the uchicago site states it assumes a deltaT figure in order to run the program. I have gone back over more threads here, and found some excellent information on the ‘best of greenhouse’ thread, although nothing which answers my question in a quantitative sense. maxwell makes a lot of sense but there are some other inputs – mostly regarding adiabatic lapse rates where I think people are confusing the adiabatic lapse rate with the environmental lapse rate. Either way, I can find no real-world measurement of the contribution of CO2 to the GE. This, to me is absolutely crucial to the debate. If one doesn’t know how much effect CO2 has initially (I take ‘initially’ to be circa 1850), how can one know how much effect an increase is likely to have?
Also, there is a very interesting discussion at the end of the thread Confidence in Radiative Transfer Models, between Vaughan Pratt, Fred Moolten, Pekka Perilla, Jan Pompe, Jeff Glassman, and others. Not sure where to pick up this conversation, but here are a few excerpts:
For a weak isolated line with a broad band source, the response is linear with concentration or mass path. That isn’t B-L either. As the center of the line becomes saturated, the response becomes square root as long as the bandwidth of the radiation is much wider than the line wings. But that’s an isolated line with a Lorentz line shape in a homogeneous medium with constant temperature and pressure. The behavior in the wings of the CO2 band in the atmosphere is complex with contribution from different altitudes with different temperature and pressure resulting in different line widths. Below 10 ppmv, the response becomes linear. Above 10 ppmv, the emission is a logarithmic function of partial pressure up to at least 1000 ppmv and possibly much higher.