Planck’s Law and the theory of blackbody radiation proves why low frequency/energy photons (eg 15um photons from CO2) cannot transfer any quantum energy to a higher frequency/energy/temperature blackbody because all of those lower frequency/energy microstates & orbitals are already completely filled or saturated in the hotter body. This fact alone from quantum mechanics falsifies CAGW.
As shown on these calculated Planck blackbody curves from 220K to 320K, CO2 (+H2O overlap) absorbs and emits in the LWIR [LongWave InfraRed] the same as a true blackbody would at an emitting temperature of ~217K over the LWIR band from ~12um to ~17um:
To falsely assume that a photon of any energy level can be thermalized by a blackbody at a given temperature would result in the dashed red and blue function in fig 4.8, which does not happen in nature. Therefore, Planck devised quantum theory to explain why blackbodies instead follow a Planck curve shown by the solid blue and red lines below (corresponding to different blackbody temperatures) and contain "cutoff frequencies for thermalization":