That means the emission probability for excited CO2 (and
water vapor) is significantly greater
than zero and explains the observed emission
spectra which show strong CO2 (and
water vapor) emission spectral features rather
than the continuum emission that would be expected if nitrogen emission dominated.
It is easy to see that the
spectrum of outgoing IF at CO2 and
water vapor absorption wave lengths are lower
than what would be expected from the surface temperature of the earth.