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Old 21st June 2010, 03:54 PM   #20
Trakar
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Originally Posted by Ziggurat View Post
It's got a hell of a lot to do with atmospheric pressure (and thickness). Atmospheres circulate. When air rises, it expands and cools, and conversely, when air drops, it compresses and heats. Air at lower altitudes is hotter than air at higher altitudes in large part because of adiabatic expansion and compression. This works out to roughly 10 deg. C per km, both on Earth and on Venus. So the fact that Venus's atmosphere is so much thicker than Earth's atmosphere is the primary cause of its dramatically higher surface temperature. Conversely, Mars has a much thinner atmosphere, and is much colder, despite being primarily CO2.
Surely, you aren't echoing Mr Goddard and trying to bring WUWT woo pseudoscience into a legitimate discussion of Venus,...are you?

"adiabatic" - occurring without loss or gain of heat

Highly unlikely with respect to Venus and the issue of its atmospheric and surface heat content. There are some adiabatic processes playing important roles in the atmospheric physics of Venus, but by definition, adiabatic processes are energy neutral, and don't seem particularly relevent to issues of Venus' surface/atmosphere heat, nor any proposed nullification of the CO2 greenhouse effect.

I'd recommend "The Recent Evolution of Climate on Venus" Bullock & Grinspoon as a good reference on Venus's heat.
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