date: Thu, 01 Jul 2004 08:35:15 -0600
from: Tom Wigley <wigleyatXYZxyz.ucar.edu>
to: Sarah Raper <sraperatXYZxyz-bremerhaven.de>
By the way, I would expunge the alternative title.
The fact that we can use MAGICC with a standard
(and constant) sensitivity and get excellent results
demonstrates that it is a very useful concept. Further,
my work with volcanoes and PCM (and all the other
forcing cases we have done with PCM that I have
considered) shows that it works for different forcings
and for forcings operating on very different timescales.
Are you trying to get IPCC to reject MAGICC? This
is what it looks like with that subtitle.
I don't think we understand variable sensitivity, but this
is a secondary and relatively minor problem. Constant
sensitivity usually works well. If some models appear to
have a changing sensitivity then so what -- is this just a
model artifact, or is it something that may apply to the
Another issue is that, because sensitivity varies spatially,
if the pattern of forcing varies in time then the global
senstivity will appear to change in time -- unless one
is careful in how the global sensitivity is extracted from
the AOGCM results.
I would urge caution in what you say.