Re: Open Source Climate Modeling was Re: [asa] Crop Yields Face Non-Linear Effects Due to Climate Change

From: Dave Wallace <>
Date: Tue Sep 15 2009 - 08:36:58 EDT

Rich Blinne wrote:
> The study used CCSM3 (Common Climate System Model 3). This is an open
> source model so that differential studies can do true apples to apples
> comparisons. As with all weather and climate circulation models CCSM3
> solves Navier-Stokes fluid flow equations which as you probably know
> is notoriously sensitive to proper initial conditions. When used in
> climate modeling the approach used by thermodynamics is used in order
> to get useful results far into the future, averaging. The model is run
> multiple times, with slightly different initial conditions, and then
> an average is computed. The spread of the runs gives a sense of how
> accurate the results are.
Another good way is to run the models with floating point precision
doubled for example 128bit float rather than 64 bit float. I realise
that not many processors support 128 bit float but some do, Power PC/AIX
does and I can't remember but possibly Sun, Alpha or SGI as well.

> Climate models are counter-intuitive in that they are less accurate on
> shorter time scales than on longer ones. We want them accurate at
> *all* time scales, short, medium, and long.
How do we know they are more accurate on longer scales? How long is

Dave W

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Received on Tue Sep 15 08:37:56 2009

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