CO2 is heavier than air (1.51 while oxygen is 1.1 and nitrogen is 0.97), however when combusted, it will initially rise until it's temperature gets closer to that of air (about 1000 feet), then it will tend to fall. CO2 is a reluctant defusser and mixer, so how does it get from 1000 to 10,000 feet - what lifts CO2 up?
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4$\begingroup$ The premise of this question is incorrect. I answered this very question years ago at physics.SE: Why does the composition of the air does not change with altitude? $\endgroup$– David HammenOct 22, 2020 at 5:30
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1$\begingroup$ @DavidHammen For the oceans without mixing, the equilibrium salt concentration goes up exponentially with depth, by a factor of e for each 10 km or so. It would be interesting to know the corresponding composition variation for an unmixed atmosphere. $\endgroup$– Keith McClaryOct 28, 2020 at 2:57
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...so how does it get from 1000 to 10,000 feet - what lifts CO2 up?
Hmm... how does it get to the mid-troposphere and higher?
Well, first, to understand that one may find some helpful information in comments below the question. Second, it always helps to review our own assumptions.
In the question, there's an implicit assumption that CO2 does not mix with the rest of the atmosphere at the molecular level. As it turns out, it does!
Also, the primary mixing mechanism in the troposphere takes place through eddy diffusion, not molecular diffusion, and that's an important distinction. Storms and jet streams, convection, and turbulence (from storms and clouds down to the nearly molecular size) all contribute to mixing.
As one goes higher in the atmosphere, the balance between the magnitude of eddy diffusion and molecular diffusion shifts. This happens above the tropopause.
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$\begingroup$ You have some good points but as a Stack Exchange answer it should focus on answering the question and not be a commentary on it or target its author. I understand that right now you can't add comments (once you reach 50 reputation points you will be able to) so you can't ask the OP to clarify their post. If you can tweak this a little bit into a more positive contribution of knowledge rather than a critique of the question, I'll give you an up vote and help you to get to that 50 threshold. Ping me by adding
@uhohto a comment here (you can always reply under your own posts). Thanks! $\endgroup$– uhohNov 6, 2020 at 2:35 -
1$\begingroup$ @uhoh, Thanks for the feedback. Positivity and encouragement is almost universally a good thing. My responses do not always come out as in line with my over-arching aspirations. :-b $\endgroup$– BruzoteNov 20, 2020 at 21:51
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1$\begingroup$ Thanks for the edit! I've made some adjustments so that this answers the question itself for the benefit of all future readers (our target audience), rather than talking to the OP directly. (generally, when we find ourselves using "you" in a sentence, we should stop and consider refactoring the sentence) If you could edit further and incorporate a few key points from the comments that you allude to but don't yet mention, this will be a perfect answer! $\endgroup$– uhohNov 21, 2020 at 1:37