[EMAIL PROTECTED] wrote:
> It isn't obvious to me why a world that is say 3C warmer couldn't have
> a dramatically different cloud distribution/appearance, sufficiently
> so that this feedback might add/subtract 5 W/m2 in addition to the
> water vapour feedback.
>
> Is this feedback somehow excluded as well (by holding cloud albedo
> constant???), or is there a good reason to presume that cloud response
> and water vapour response to increased temperature will be smooth?
There's no proof of this, but no-one has yet managed to produce a
credible model (or perhaps any model at all) where there is a strongly
nonlinear response. The limited data make it seem unlikely (we've had
10xCO2 in the past).
Actually I should admit that we have found some models that switch into
a runaway Venus-like state when they get hot enough (by which I mean
+10C, and they had a warm bias to start with).
We haven't yet checked out the cause of this, it may just be some
implausible extrapolation of a parameterisation into a nonphysical state
(noting the extreme temperature which the model was not really designed
for). OTOH, it might make a great Nature paper about runaway warming.
Perhaps we shouldn't look too hard.
James
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