Just to give an example, the mean free path length of photons in the CO2 at its current density in the atmosphere is 48 meters. (wattsupwiththat.com)
The group sought to establish a framework and tool to measure the mean free path distribution in a number of technologically interesting materials. (sciencedaily.com)
At these heights any remaining CO2 is basically irrelevant because the mean free path for absorption is of the order of kilometers. (wattsupwiththat.com)