Why the Atmosphere is Thermally Asymmetric.

One concept which exists in Physics is, that if a surface has a greater coefficient of absorption, to one specific electromagnetic wavelength, then the degree with which this surface will emit EM radiation, at the same wavelength, due to incandescence, will also increase in a linear fashion. This is also known as Kirchhoff’s Law.

This fact seems to contradict what has been observed in the Earth’s Atmosphere, regarding how an increase in CO{2} levels has led to warming of the planet. It would be tempting just to assume casually, ‘The Earth’s Radiation of heat into space is low-temperature incandescence, Why does it not increase in-step with thermal absorption?’ And while there are several answers to this question, all of which require a more-complex analysis of what happens in the atmosphere, or of how the Sun is different from the Earth, this posting of mine will focus on one of the answers, which may also be the easiest to understand.

The temperature of the atmosphere at sea-level, may be around 20⁰C wherever it’s Summer. But at an altitude of 15km, the atmospheric temperature is close to -70⁰C. What this means is that, along with actual surfaces of the planet, the CO{2} in the lower layers of the atmosphere may be radiating electromagnetic radiation – i.e., deep infrared light – towards space. But because at an altitude of 15km the atmosphere also contains a matching level of CO{2}, those molecules in the upper atmosphere will mainly just catch this radiation again, and transform it back into stored heat. ( :1 )

So what happens among other things, is that an atmosphere differs from a surface of matter, and from the basic principle mentioned above, in being asymmetric. And what makes it asymmetric, is Gravity. It’s much more difficult for heat to escape, than it is for heat to be absorbed. Now, if there was some way to make the temperatures in the upper atmosphere not-different from those at lower altitudes, then the effect of global warming might not even take place. But the atmosphere’s CO{2} ‘which space sees’, is in the upper atmosphere, which is constantly very cold, while the atmosphere’s CO{2} ‘that humans see’, is at sea-level, which has the (increasing) temperatures we witness in everyday life.

Now, I have never been asked to provide this information. But seeing as there seems to be a question in Physics, which nobody else provides an answer for, and which nobody else seems to recognize as existing, I felt I should spontaneously provide an answer here.

(Updated 04/22/2018 : )

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