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# On the finiteness of the atmosphere

I guess the funniest thing I ever saw was a person driving down the highway in a Toyota Prius smoking a cigarette with the windows closed. It was like they were telling me, “I respect your atmosphere but not mine.” That got me thinking, does human generated, gaseous, atmospheric pollution actually make up a significant part of the total atmosphere, and can it possibly affect it? In other words, is this merely a very delicate series of calculations one must carry out to see that the atmosphere, and us, can be affected by gaseous pollution?

So, what I set out to do was determine how much pollution is generated and compare that to the volume of the atmosphere. The first aspect is easy. There are numerous sources of data on the amount of carbon dioxide (CO2) and other chemicals generated on Earth every year. We know how much power is used by all the societies on Earth and that burning fossil fuels generates a given amount of pollution, so, we can determine there is about 33,000,000,000,000 kg of CO2 produced each and every year. That is 33 with twelve zeros after it or 3.3 × 1013 kg-CO2.

This is a big number by any measure. How big is it compared to the atmosphere? The Earth is huge, as is the atmosphere, so how can even such a large amount of CO2 even compare to the size of the atmosphere?

The atmosphere is most dense at the surface and gradually decreases in density (or equivalently pressure) until it fades to nothingness. This doesn’t help much.

To find out how much atmosphere there is one must remember the definition of pressure. If I were to step on your foot with my flat soled shoe it may hurt, however, if I were to step on your foot while wearing a high heel it would certainly hurt. (I don’t have a pair of high heels, this is merely a visual metaphor…) The difference is pressure, force per unit area.

I have the same amount of mass, it’s just that I concentrate it on a smaller area when wearing high heels and the pressure is greater. I know the pressure of the atmosphere and I know the area of the Earth’s surface, so, I can easily calculate the mass of the atmosphere. It is actually 5,200,000,000,000,000,000 kg (5.2 × 1018 kg)!

The amount of atmospheric CO2 is actually measured in parts per million or ppm, in fact its ppm measured on a molar basis which is a way to compare the number of CO2 atoms to the number of atmospheric atoms. I can convert kg’s to mole’s to find that my calculation gives 4.2 ppm. This is the amount of CO2 generated every year and adds to the previous year’s total concentration since CO2 has a very long lifetime.

This can be compared to how much CO2 is in the atmosphere right now. It has been measured at the Mauna Loa volcano in Hawai’i since the late 1950s, where it was a little under 320 ppm, to now where it is approximately 400 ppm. Recently, the rise in CO2 has been about 1.7 ppm per year.

The annual emission of CO2 is 4.2 ppm, and the data shows there is a 1.7 ppm annual increase, why the difference? Firstly, it’s important the numbers are about the same validating the above estimate. Secondly, it is known the oceans acidify when CO2 is absorbed by water to make carbonic acid and accounts for some of annual reduction of CO2 in the atmosphere. Some is also absorbed by the land and trees.

One cannot deny the CO2 concentration increase is due to human activity. The atmosphere is truly finite in size despite its perceived largeness from one’s isolated view.

Featured image credit: The atmosphere outside my apartment building by Michael E. Mackay. Used with permission.