Reddit reviews Global Physical Climatology (Volume 56) (International Geophysics (Volume 56))

The problem is that there is a huge difference in the basic knowledge refuting this statement -

> It's still hard to imagine that C02 is causing that greenhouse effect, for the proportion reasons commonly stated.

and the far more complicated scientific reasoning involved with detailing this one -

> I'd really like to read a paper about the exact numbers involved in calculating the C02 impact on the greenhouse effect

That increasing atmospheric CO2 concentrations enhances the greenhouse effect is evident from basic physical climatology dating back over a century, to the work of Arrhenius, Tyndall, and Fourier. It's not "hard to imagine" in the slightest when you start digging into the nuts and bolts of radiative transfer theory. But you'll need to dig for quite some time in that body of literature to get to the direct computations of CO2 impact on the greenhouse effect. Such work is done by line-by-line radiative transfer code, like MODTRAN.