To
understand how cloud feedback might work, you have
to understand some facts about clouds:
(1)
Clouds absorb radiation in the infrared, and therefore
have a greenhouse effect on the climate.
If you
put a cloud high in the
atmosphere, it will have a stronger
greenhouse effect than if you put it low in the atmosphere.
(2)
Clouds reflect sunshine back to space.
So more clouds
means less sunshine for earth. If
you put a cloud
high in the atmosphere, it will reflect about the same
amount of sunshine as if you put a cloud low in the
atmosphere.