Water vapor of course is the most abundant greenhouse gas in the atmosphere and is responsible for the majority of greenhouse effect. It is often left out of the debate (and its accompanying charts) altogether, which I find puzzling. The explanation for brushing aside this top contributor is the fact that water vapor is seen as a 'feedback' greenhouse gas rather than a 'forcing' green house gas. That is to say that it increases in reaction to warming as well as functioning to perpetuate and exacerbate it. Indeed, CO2 can't be excluded from this characterization, either. How is it purported that the characterization of feedback and forcing negates the fact that atmospheric H2O levels have risen, and that it is the most effective contributor to greenhouse effect? Granted a warming trend, why isn't water vapor the preeminent target for climate change study? It is also contended that water vapor remains in the atmosphere for just over a week at most, while CO2 could stay afloat for decades. Nevertheless, with water vapor levels rising on aggregate, how does this fact negate the effectiveness of atmospheric H2O as a greenhouse gas? Where the ins and outs of CO2 and CH4 are being poured over diligently, apparently for their capacity to implicate human contribution, why is there so little earnest exploration of the role good 'ol water plays? The big role.