I'm not sure how useful that analogy is since the few cups of additive in the swimming pool (natural CO2 in the natural atmosphere) make the difference between warm and rather cold (water vapor alone is not going to keep the earth warm). My preference in those cases is the political argument. Use the swimming pool and show us shrinking our economy when we take out a few cups of water (CO2 is proportional to economic activity). Now show China dumping gallons in (they are building two coal based power plants a week). The science is hopelessly politicized since the government has bought the research results they want (that calls for more government control). So at this point politics should be the preferred mode of argument. Huh? Keep it simple when debating, I got a headache reading your response.