[ROCKLOBSTER]

I would be more persuasive, which requires some kind of art.

OK.

78% = Nitrogen (is that a "greenhouse gas"?)
21% = Oxygen (is that a "greenhouse gas"?)
.9% = Argon
99.9% is the total so far

Is the rest of that 0.1% (1/10th of a percent) CO2?

[aspasia]

And an image mapping the layers of the atmosphere for a 2-page summary.