How much do we really know about how CO2 works in our atmosphere?

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Offline norcalclimber

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I decided to look at how CO2 is measured in our environment, and what I learned has brought some questions to mind.

"Mole fraction in dry air

What do we need to measure? Most people assume that we measure the concentration of CO2 in air, and in communicating with the general public we frequently use that word because it is familiar. The quantity we actually determine is accurately described by the chemical term “mole fraction”, defined as the number of carbon dioxide molecules in a given number of molecules of air, after removal of water vapor. For example, 372 parts per million of CO2 (abbreviated as ppm) means that in every million molecules of (dry) air there are on average 372 CO2 molecules. The table below gives an example for 372 ppm CO2 in dry air. All species have been expressed as ppm, turning 78.09% nitrogen into 780,900 ppm. The rightmost column shows the composition of the same air after 3% water vapor has been added:"

We see from their graph, that when 3% water vapor is present we only have 360ppm of CO2.  Since the amount of water vapor varies dramatically from day to day, then the amount of infrared light which can be absorbed by CO2 in any given area must vary dramatically.  But the amount of CO2 in the atmosphere doesn't really change just because some water moved into the area, only the ppm, so where does it go? 

Or does it not go anywhere, because the water laden air simply has more molecules per square inch and therefore a given area would still have the same amount of CO2 with 3% water as with 6%?

The page goes on to say that there is more CO2 in the Northern Hemisphere than in the Southern.  Even at the Mauna Loa observatory, we see that they don't get exactly the same result for ppm on every test, in fact we see that the amounts can change dramatically. 

So it seems to me, that saying we have 372ppm of CO2 in the atmosphere is more than a bit lacking when it comes to explaining the situation.  Instead, it seems the amount of CO2 in the atmosphere over any given area changes dramatically both from air currents and displacement by water. 

Do we have any idea at all how these "flows" of different concentrations of CO2 affect weather on a global scale?

Variations in Earth's magnetic field and rotation also means that given areas receive varying amounts of cosmic radiation;  How does changing concentrations of CO2, water vapor, and cosmic radiation affect our weather on even a local scale let alone a global one?

Since we admittedly have very little understanding of all the dynamics of water vapor, which seems easier to test than CO2, and it can dramatically affect concentrations of CO2, it seems to me that we actually know extremely little about global climate dynamics.

I am far from an expert in this field, so hopefully someone can explain to me where I may have gone wrong in my understanding of the science.