yellow, and the peak emission range of outgoing radiation is colored blue (though of course some emission occurs from both sources outside those ranges)[1].
Fig. 4.2
Note the fact that incoming solar radiation is not absorbed efficiently by any molecule, whereas outgoing radiation is efficiently absorbed by a number of molecules, particularly carbon dioxide, nitrous oxide, water vapor, and ozone. This is the source of the greenhouse effect.
A more apt metaphor for the effect, then, might be the “one-way mirror” effect. Rather than acting like a greenhouse (which suppresses convection), the presence of a heterogeneous atmosphere on Earth acts something like an array of very small one-way mirrors, permitting virtually all incoming radiation to pass relatively unimpeded, but absorbing (and later re-radiating) much of the energy emitted by the planet itself. Of course this too is just a metaphor, since true mirrors are reflective (rather than radiative), and changing the reflection profile of the system (as we’ve seen) changes the albedo, not the radiative values. Moreover,
- ↑ Figure adapted from Mitchell (op. cit.)
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