The CRU Info Leak . . .
I’m thinking there just might be some problems in some of the GCM software.
In the middle of October 2009, Tom, Gavin, Mike, and a bunch of other people discuss models, measured data, and presentation of comparisons.
I’ve added some bolding.
See the whole thing to ensure that The Context is proper.
From: Tom […]
To: Gavin […]
Subject: Re: BBC U-turn on climate
Date: Wed, 14 Oct 2009 16:43:54 -0600
Cc: Michael […], Kevin
[…], Stephen […], Myles […], peter […],
“Philip […], Benjamin […], Thomas […], Jim, Michael […]
I just think that you need to be up front with uncertainties
and the possibility of compensating errors.
Gavin […] wrote:
> Tom, with respect to the difference between the models and the data, the
> fundamental issue on short time scales is the magnitude of the internal
> variability. Using the full CMIP3 ensemble at least has multiple
> individual realisations of that internal variability and so is much more
> suited to a comparison with a short period of observations. MAGICC is
> great at the longer time scale, but its neglect of unforced variability
> does not make it useful for these kinds of comparison.
> The kind of things we are hearing “no model showed a cooling”, the “data
> is outside the range of the models” need to be addressed directly.
> On Wed, 2009-10-14 at 18:06, Michael […] wrote:
>> Hi Tom,
>> thanks for the comments. well, ok. but this is the full CMIP3
>> ensemble, so at least the plot is sampling the range of choices
>> regarding if and how indirect effects are represented, what the cloud
>> radiative feedback & sensitivity is, etc. across the modeling
>> community. I’m not saying that these things necessarily cancel out
>> (after all, there is an interesting and perhaps somewhat disturbing
>> compensation between indirect aerosol forcing and sensitivity across
>> the CMIP3 models that defies the assumption of independence), but if
>> showing the full spread from CMIP3 is deceptive, its hard to imagine
>> what sort of comparison wouldn’t be deceptive (your point re MAGICC
>> perhaps Gavin has some further comments on this (it is his plot after
>> On Oct 14, 2009, at 5:57 PM, Tom […] wrote:
>>> The Figure you sent is very deceptive. As an example, historical
>>> runs with PCM look as though they match observations — but the
>>> match is a fluke. PCM has no indirect aerosol forcing and a low
>>> climate sensitivity — compensating errors. In my (perhaps too
>>> view, there have been a number of dishonest presentations of model
>>> results by individual authors and by IPCC. This is why I still use
>>> results from MAGICC to compare with observed temperatures. At least
>>> here I can assess how sensitive matches are to sensitivity and
>>> forcing assumptions/uncertainties.