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Scattering from CO2 is where a photon hits it with an energy in one of the CO2 resonance bands and knocks it to an internal excited state of vibration. After a bit, the excited state drops back to "normal" and emits the photon at that same wavelength. If that didn't happen CO2 industrial IR lasers would not work. In the time between absorption and reemission, the CO2 molecule has rotated to a different random position and emits the photon in a random direction. If the direction is away from earth, it will continue on and hit another photon within an average distance of around 6 meters. If the photon heads for earth and is not absorbed by another CO2 molecule, it will hit earth and be absorbed. That process is all quantum mechanics. Thermodynamics does not enter at that point. That is what backscattering is. You are right that it doesn't retain that energy, it just redirects it.
Scattering from CO2 is where a photon hits it with an energy in one of the CO2 resonance bands and knocks it to an internal excited state of vibration. After a bit, the excited state drops back to "normal" and emits the photon at that same wavelength. If that didn't happen CO2 industrial IR lasers would not work.
In the time between absorption and reemission, the CO2 molecule has rotated to a different random position and emits the photon in a random direction. If the direction is away from earth, it will continue on and hit another photon within an average distance of around 6 meters. If the photon heads for earth and is not absorbed by another CO2 molecule, it will hit earth and be absorbed. That process is all quantum mechanics. Thermodynamics does not enter at that point. That is what backscattering is. You are right that it doesn't retain that energy, it just redirects it.
