[exDemMom]

It depends on the ratio of the mean time bewteen collisions to time between absorbtion and reemission. Down in the dense atmosphere, the molecules have a high probability of colliding while in an excited state, the collision converting some of the energy of oscillation to kinetic energy.

In other words--trying to calculate any effect of shining any light of an excitatory wavelength into a gas must be a bear and a half. It's especially complicated since the atmosphere is an open system, not a closed... Also, given that all gases have emission spectra, it'll be REALLY hard to separate out the total contribution of only the IR portion of the CO2 emission spectrum to the overall kinetic energy, as opposed to the contribution of all the other gasses at all wavelengths.

[Lonesome in Massachussets]

The calculations are straightforward, given the system state. No one knows the system state. The warmmongers mistake confidence in their calculations, given the system state for confidence in their knowledge of the state of the system. You are correct, it is almost impossible to know the system state, even a posteri, much less predict a day in advance.