From: John Beckett 

"Geo."  wrote in message
news::
> it's just that CO2 itselfs has some capacity to absorb/reflect sunlight
> so for that to make a difference you need a significant amount in
> comparison to the total atmosphere since you are talking about
> atmosphereic change.

Negative on that batman.

The CO2 does its stuff regardless of the rest of the atmosphere (except
that apparently there is some nonlinear interaction between the various
greenhouse-effect gases).

You could remove all the nitrogen and oxygen from the atmosphere and have
no effect on the greenhouse effect of CO2 (I think).

The proportion of CO2 is simply not relevant.

The issue merely concerns the probability of whether a photon of infrared
radiation escaping from earth would be captured by hitting a CO2 molecule.

That probability is determined by how many CO2 molecules there are per
square meter of earth. The fact that there is a huge quantity of nitrogen
and oxygen merely allows the photon to travel a long way vertically before
either hitting a CO2 molecule, or continuing to space.

John

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