DrNickBone wrote:
On 14 Jan, 09:44, William Connolley <[email protected]> wrote:
2010/1/13 Alastair <[email protected]>:
On Jan 13, 10:41 am, DrNickBone <[email protected]> wrote:
Reasonable GCMs do sometimes show runaway warming
They show a fully cloud covered earth, similar to the outward state of
Venus, but they do not show a boiling away of the Earth's oceans.
{{cn}}, both of you.
-William
I was referring to a comment by James Annan earlier in the thread
(post of 4th January)
GCMs can achieve runaway warming - in fact some informal conversations
suggest to me that this is rather more common than you might imagine
based on reading the literature - but this is generally attributed to
some nonphysical behaviour such as a parameterisation extrapolated
beyond its valid range. However, I don't believe that Pierrehumbert's
handwaving with simple approximations can really refute calculations of
state of the art climate models.
I'm not sure which models James was thinking of. But if he is right
at least some have reached the literature, with others hiding in
the filedrawer marked "Uh-oh".
Personally, I'd consider it an academic point whether the oceans
literally boil away in these models, or the Earth comes back into
a new equilibrium with very high albedo. A cloud-covered Earth with
minimal or no life under the clouds is still an awful thought.
I don't believe any have reached the literature, and none of them get
anywhere near boiling point, the models crash at much cooler temperatures.
Um....if you really need a citation, some are mentioned in
http://www.clim-past.net/5/803/2009/cp-5-803-2009.html
It is not just the perturbed parameter stuff that does this, "ordinary"
models sometimes manage it while under development, or under very high CO2.
Righty or wrongly, it seems that no-one takes it seriously in physical
terms. I expect if cpdn had found models like this it would have been
headline news, but they only found spurious cooling which was
"obviously" unphysical :-)
James
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