I want to do an experiment by fixing individual GHG's one by one. How can I do this in RegCM4.6? I found an option under ICBC Global data input control but it is fixing all the GHG's at the same time. Please help.
You can make comparisons of relative effects of greenhouse gases using models, such as this one by the Univ. Chicago.
http://climatemodels.uchicago.edu/modtran/
You cannot make an experimental comparison because most of the greenhouse effect depends on specific temperature of the scale height for atmospheric escape for each gas at its near-surface location.