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Originally Posted by Starfury
If these clouds are clean (i.e. consisting of evaporated water), they will keep in more energy than they keep out, causing a rise in temperatures.
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but about all clouds consist of
condensated and
frozen water. and they cause less energy to be absorbed from the sun, which is easily understandable: in the sun it is warmer than under cloudcover; also from space cloudcover is white and water/land rather dark. bodies with dark surfaces get hotter in the sunlight than bright ones do.
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Originally Posted by Starfury
If, on the other hand, the clouds are dirty, they'll block out more sunlight than they'll keep in, causing a drop in temperatures (extreme example: nuclear winter).
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rather rare. the best example is the eruption of the st. helens in 1980, the dust it carried into the atmosphere actually caused colder weather for a few years. that way we had more white christmases in the early 80s. it was great, we had so much fun in snowball battles, sleighing and i built the most wonderful snowmen:-)
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Originally Posted by Starfury
So if we have a global warming, we can't count on the generated clouds to cool us back down, they'll do exactly the opposite.
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that is not true.
clouds make it colder, however water
vapor in the atmosphere that is
not condensated into clouds does work as a greenhouse gas like CO2, CH4..., letting VIS range EM pass but absorbing in the IR range.