CO2 reflecting IR back to space?

Question

If CO2 is responsible for trapping heat as a result of IR radiation not being able to pass through the "ever thickening layer of Carbon Dioxide"

Then what happens to the IR radiation that hits earths atmosphere that has been emitted from the sun itself.

Answer 1

It is absorbed, (a lot of it by the CO2).

Thats how the CO2 traps heat.

It absorbs and emits energy in the infra-red, (heat), range.

Other wavelengths escape more easily.

Answer 2

The important thing to note is that most of the time it ISN'T IR radiation coming from the sun. The sun is much hotter than the earth, so it's blackbody radiation spectrum is closer to the visible. The earth absorbs most of this, and radiates it back at a longer wavelength (i.e. deeper into the infrared).

Think about what happens when you heat a piece of iron, or a light bulb filament. At first, you won't be able to see much (but you can feel the heat radiating off it - this is infrared). Then, as it gets hotter, it will emit a slight red glow. Hotter still, it will be white hot (such as the light bulb filament). Shorter and shorter wavelength with increased temperature.

Since the visible light from the sun is hardly absorbed at all, but CO2 absorbs the infrared light as it is being radiated by the earth, the net effect is to trap heat in the earth's atmosphere.

Edit for clarification:

I didn't say that the sun didn't emit infrared, I said it mostly isn't infrared - the spectrum is shifted to the shorter visible wavelengths.

A fairly typical photon from the sun will pass through the earth's atmosphere relatively unimpeded because it will lie in the visible portion of the EM spectrum. It will heat up the earth, a hotter earth radiates more energy back into space. A fairly typical radiated photon from the earth, however, will be deeper into the infrared, because surface of the earth is colder than the surface of the sun. This photon will likely be absorbed on its way out of the atmosphere.

Some photons from the sun lie in the infrared. Some of the visible photons will be absorbed anyway, and some of the infrared photons from either the sun or the earth will make it through anyway. But playing the averages, the net effect is to warm the earth.

Answer 3

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