The blame game

The IPCC, and many other official bodies prefer to place most of the blame on CO₂. Elsewhere, it argued that Φ is the main cause of global warming: "Whenever three or more contrarians are gathered together, one will inevitably claim that water vapour is being unjustly neglected by 'IPCC' scientists. Why isn't water vapour acknowledged as a greenhouse gas?", "Why does anyone even care about the other greenhouse gasses since water vapour is 98% of the effect?", "Why isn't water vapour included in climate models?"...Long-wave (or thermal) radiation is emitted from the surface of the planet and is largely absorbed in the atmosphere. Water vapour is the principle absorber of this radiation (and acknowledged as such by everybody). But exactly how important is it?

In terms of mass, water vapour is much more prevalent (about 0.3% of atmospheric mass, compared to about 0.06% for CO₂), and so is ~80% of all greenhouse gasses by mass (~90% by volume)....it's clear that water vapour is the single most important absorber (between 36% and 66% of the greenhouse effect), and together with clouds makes up between 66% and 85%. CO₂ alone makes up between 9 and 26%, while the O3 and the other minor GHG absorbers consist of up to 7 and 8% of the effect, respectively [w03].