Water vapor is the predominant greenhouse gas in the atmosphere and mostly maintains the planet’s temperature; however, as carbon dioxide, methane and other non-condensable greenhouse gases are added, this further amplifies the greenhouse effect and raises temperatures further. Besides increasing evaporation rates, the warmer air is able to hold additional water vapor (a condensable greenhouse gas). Warmer temperatures, also, ramps up the rate at which permafrost and oceanic hydrates melt, thus releasing more and more ‘methane’. This further amplifies the greenhouse effect and, thus, increases temperatures that again, in turn, causes increased levels of evaporation and melting. The even warmer atmosphere can now hold even more water vapor, which, of course, is a greenhouse gas... repeat... repeat...
Note: To read about what happens when greenhouse gas levels are decreased to abnormally low levels, search:
‘Snowball Earth + cyanobacteria’
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