"CO2 as a greenhouse gas is such a small part of the equation by itself."

I just explained to you that under average conditions, the wavelength of a photon is 330 times larger than the average spacing between CO2 molecules in our atmosphere, that's a hell of lot of chances for interaction. Seriously Richard, go read the link I posted from a P Chem professor and get back to me. Your comment is like saying arsenic isn't poisonous because it only takes a little to kill me. 

"We need to include other forcings that drive climate, and for the most part they are left unmentioned."

Richard, richard, richard, this dead horse has been beaten ad naseum. CO2 is the primary driver of the observed planetary energy imbalance. I'm serious, this is something you can directly measure. The energy that's being absorbed in the top of the atmosphere shows CO2's fingerprints. 

http://shadow.eas.gatech.edu/~kcobb/warming_papers/Hansen05.pdf