[JasonC]

There is no "pound for pound" about it, since it isn't a linear relationship. Water vapor contributes nearly all greenhouse power, but the sky is largely saturated with water vapor - meaning, opaque from below to the wavelengths of infrared light that are absorbed by water. There are marginal differences tied to weather from variations in humidity (e.g. in deserts the sky is not opaque to those wavelengths, unless covered by cloud cover).

CO2 can matter (though only marginally because it is so trace a gas) because the sky is largely "clear" in those wavelengths. But this changes as the CO2 level rises. The response is log rather than linear; the second doubling of the concentration does much less than the first. Close your window shades. How much would it matter if you hung 4 more sets of shades behind them?

[ETL]

Thanks! Are you in the field, or did you just sleep at a Holiday Inn last night? :)

Seriously. Thanks. Sounds like you know what you’re talking about.

[ETL]

Re: CO2 greenhouse gas analogy...

Close your window shades. How much would it matter if you hung 4 more sets of shades behind them?

Expotentially less and less with each additional shade. Excellent point. Thanks again.