If CO2's molecular weight is 3x heavier than air, how can it rise into our atmosphere

Perito · Dec 23, 2009, 09:55 AM

Air (nominally 80% nitrogen, 20% oxygen) and Carbon Dioxide are completely miscible in all proportions. Although it's heavier than air (air has an average molecular weight of 28.8 vs carbon dioxide's molecular weight of 44 -- so it's not three times heavier than air), it still dissolves in air and can be dispersed throughout the atmosphere of the world.

The theories behind global warming say that the CO2 molecule, wherever it is (high or low in the atmosphere) absorbs light from the sun and converts it into heat.

There is discussion of the amount of CO2 that is absorbed by the world's forests. That's one of the points of contention -- some people say it's more than others say.

(This is a question that should have been posted under Chemistry.)

Unknown008 · Dec 23, 2009, 10:55 AM

Also, if you consider the equations involved, photosynthesis converts carbon dioxide to oxygen in the ration 1:1.

$6CO_2 + 6H_2O \rightarrow C_6H_{12}O_6 + 6O_2$

At the same time, in respiration in living things, the ratio of oxygen to carbon dioxide is the same.

$C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O$

Looking at those only, adding a surplus of carbon dioxide will tend to remain in the atmosphere and not used in photosynthesis.

Now adding other factors like photosynthesis occurs only in the presence of light, things are being burnt in uncontrolled amount at times, the effect of marine organisms which also try to decrease the amount of carbon dioxide, the plants which have a higher rate of photosynthesis due to the increase in carbon dioxide... All those if considered may make anyone's head hurt. That is why, I prefer referring to those two equations first.

The overall result though, is that the amount of carbon dioxide in the atmosphere is gradually increasing.

If CO2's molecular weight is 3x heavier than air, how can it rise into our atmosphere

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