For some reason the global warming crowd doesn't talk about the fact that the primary greenhouse gas is water vapor. CO2 only makes up something like 10%, and the human caused part only about 4% of that, which is 0.4% overall.
At least according to the Wikipedia “Greenhouse gas” article, it’s hard to measure exactly how much each gas contributes to the greenhouse effect, because different gases absorb and emit radiation at different frequencies.
Regardless of how you work out the proportions, there used to be a homeostasis, where the biological and physical processes that put greenhouse gases into the atmosphere balanced the processes that took them out. The additional CO₂, CH₄, and N₂O from human activity is upsetting that homeostasis.
But is it? Where for instance does Doug Keenan go wrong?
http://www.informath.org/media/a42.htm
(an essay originally published in the WSJ 'What is arguably the most important reason to doubt global warming can be explained in plain English.'.
