@crandles... probably this should qualify as a "silly question" - if so, apologies - but going by the diagram you posted above, most of the atmospheric absorption of reflected energy is due to co2 ( in the near IR) and water vapor ( in the far IR). Is it the case that the 100% long-wavelength absorption shown in the diagram is independent of temperature/humidity, or does some proportion of this energy escape back into space when the air is too cold to harbor much water vapor?
The reason I ask is that I'm wondering if arctic far-IR absorption increasing with air temperature (especially close to 0 degrees C) , is a positive-feedback mechanism that comes into play with the presence of early melt-season open water?
I think reflected energy is the same wavelength as incoming. So I assume 'reflected' in the first sentence quoted is just a mistake and you are really talking of Earth radiating heat in infra-red.
I am not certain of the meaning of the pink, black and blue curves but assume these are something like radiation from earth at temperatures appropriate to equator, 45 degrees N or S and pole (maybe tropics, mid latitudes and Arctic/Antarctic circles).
Water vapour absorbs at near and far infra-red wavelengths. The window between these is partly covered by CO2 absorption. The window will be slightly larger for the poles because the atmosphere can hold less water vapour at polar temperature causing less widening of absorption bands with concentration of water vapour. There is also more outgoing radiation at the wavelengths covered by CO2 absorption in the window because Earth is colder at the poles as shown by black versus pink curve.
I am a bit unsure of even the above let alone speculating further.
I assume that virtually all radiation from earth escaping to space will be in or near the window. Is it fully 100% absorbed at longer wavelengths? From surface I would expect it is as near as makes no difference fully 100% absorbed. However, I would think that there must
mbe some height from which some small part escapes - this will then be atmosphere emitting to space rather than
re-absorption by atmospheredirect from earth. The distribution between wavelengths will then depend on atmosphere temperature rather than surface temperature so where atmosphere is warmer with temperature inversion there may be less radiation at those longer wavelengths. I expect this would only be a small effect near the top of the atmosphere for radiation emission.
There are bound to be others far more expert on this than me.