I have always believed that the "runaway greenhouse" was not possible
on earth, but from my point of view that is hearsay; I've never seen
the calculations.
Venus is cloud covered and this has not prevented a runaway greenhouse there.
The idea that increased column humidity necessarily leads to either
increased cloud cover or increased precipitation is not correct in
itself; you have to appeal to the complexities of the climate system.
(Current evidence is strong that column precipitation increases much
more slowly than column humidity; this has important implications for
the large scale circulation. I don't know what the projections are for
clouds and wouldn't entirely trust them. All of this, though, presumes
conditions much less catastrophic than Hansen is discussing.)
I think it's an unfair summary to say that Hansen is actually
predicting a Venuslike state for the earth; he is simply speculating
upon it under a reporter's questioning. He may be political enough to
be reluctant to say "a runaway greenhouse won't happen". But he didn't
say it will.
Amid all the gloom (which I think and hope is a bit excessive in what
we see of the Hansen interview), I remain amused by the common
grammatical form of earth scientists, the "second person planetary" as
in "But with continued rapid increase in greenhouse gases, you could
melt the ice sheets in less than a century". Who, me?
mt
--
You received this message because you are subscribed to the Google Groups
Global Change ("globalchange") newsgroup. Global Change is a public, moderated
venue for discussion of science, technology, economics and policy dimensions of
global environmental change.
Posts will be admitted to the list if and only if any moderator finds the
submission to be constructive and/or interesting, on topic, and not
gratuitously rude.
To post to this group, send email to [email protected]
To unsubscribe from this group, send email to
[email protected]
For more options, visit this group at
http://groups.google.com/group/globalchange
