I was reading about solar radiation, and there was a part that says that the atmosphere absorbs most of the radiation emitted by the sun. I wonder if when the atmosphere absorbs the energy, where does it go since energy doesn't disappear or that's what I've been taught in high school. I'm guessing it transforms to heat. Correct me if I'm wrong, and a explanation would be very appreciated.

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    $\begingroup$ Atmosphere is pretty transparent, as you might have noticed. Most of the radiation reaches us down below and gets absorbed by the plants, soil and whatever else. What little of it is absorbed by the atmosphere does indeed transform to heat. $\endgroup$ May 29 '17 at 8:40
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    $\begingroup$ There is some detail about which molecules in the atmosphere absorb ir radiation and why in the answer to this question chemistry.stackexchange.com/questions/73565/… $\endgroup$
    – porphyrin
    May 29 '17 at 9:21
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    $\begingroup$ The atmosphere also radiates heat. $\endgroup$ May 29 '17 at 17:04

It is broadly true that some solar radiation ends up heating the atmosphere. But it isn't true that the atmosphere absorbs most of the heat emitted by the sun.

Broadly there are several ways that radiation is absorbed:

  • Some of it (but not much of it) is absorbed directly by certain molecules in the atmosphere (carbon dioxide and water vapour are biggies), directly heating them.
  • Some of it is reflected by clouds and ice and other parts of the earth and reemitted to space (quite a lot of it)
  • Some radiation is absorbed by plants and used to drive photosynthesis (important but not a lot of absorbed radiation)
  • A lot of it is absorbed by the surface of the earth (land and sea) which is the part that contributes most of the warming effect of sunlight (of course this warmer sea and earth then warms the atmosphere above it either directly be contact or by being absorbed before it is transmitted back into space, though a lot of it is emitted to space).

So, in the end, a lot of the radiation ends up as heat, but mostly via heating of earth and sea not by directly heating the atmosphere. On the other hand, the atmosphere does end up much warmer as a result. And the absorption by the atmosphere does make the difference between the earth being very cold or very habitable as a planet. The details of this are very complicated which is why people build very big computer models when they want to understand global warming which depends of the complicated details of how the atmosphere absorbs fractions of the heat.


Not sure why you think this is a chemistry problem: see https://science-edu.larc.nasa.gov/EDDOCS/images/Erb/components2.gif, for example. Note that this energy diagram ignores both biological energy flow (e.g. photosynthesis, decay, burning) as well as geothermal energy flow (e.g. volcanoes) as well as processes which take hundreds, thousands, and millions of years (cooling of core of Earth). An isolated system is one which, by definition, energy is constant (although the form that that energy takes may and often does change). In common experience, the Law of Conservation of Energy and Mass holds. In more exotic situations we have to include strain or density as also part of the conserved quantity, but unless you're dealing with relativistic velocities, or gravities far heavier than that found on Earth, or with densities far greater than those found on and within several hundred kilometers of the surface of the Earth, you can ignore that and just remember that Mass is energy, and energy is conserved. The other exception is at cosmological scales where space is expanding but our best models suggest that each cubic meter of vacuum (of space) has a constant energy density. This means that as space expands, the total energy of our Universe is increasing. This is theoretical, and is disputed among experts in the field.


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