Comment Not quite that simple (Score 3, Insightful) 547
The big spoiler that makes models a bit more difficult is water vapor. It is both more prevalent than CO2 in the atmosphere and more variable in the amount (CO2 is pretty uniform, water vapour varies a lot based on location, time of year, etc). Also when you look at the absorption spectra, water vapour absorbs larger bands of IR than CO2, particularly in the thermal IR region.
That's not the only extra bit of complexity, but it is one that confounds the situation.
Now before you fly off the handle and start screaming and ranting: I'm not challenging the validity of the theory here, I'm just saying you are oversimplifying things. Going after people for being stupid, but then showing ignorance of the complexity of the issue is rather silly.
The problem is that it is complex. If it were a simple system, we'd likely have a very accurate model for it. The complexity is precisely why despite general agreement on the theoretical mechanism of action there are such wide error bars on the predictions.