Re: [asa] Freeman Dyson on Climate Change

I apologize for not giving the full details as to why I believe the
arguments were pure nonsense so let's explore the issues surrounding
fluid dynamics, approximations and parametrizations.

The foundation of fluid dynamics (which govern both the flow of
liquids in the oceans and gasses in the atmosphere) is given by the
Navier Stokes equations. These equations can be expanded to represent
the equations of motion on a rotating sphere. Further approximations
based on scaling arguments and other approximations based on the
(non)-compressibility lead to the basic equations which govern the
motion of fluids on a rotating sphere.
Such equations however cannot be solved in most cases and need to be
further 'approximated' via grid solvers which represent the ocean or
atmosphere as a three dimensional grid. Due to the differences of
scales, the horizontal grid distances tend to be much larger than the
vertical ones. Using a variety of solvers, one can obtain the motion
of particles on such grids.
Since the vertical distances are much smaller than the horizontal
distances, these models need to represent sub-grid processes in an
alternative way. Typically, such processes are parametrized and
related to the grid velocities.

Of course, many things can go wrong here. The approximations and
parametrizations can be insufficient to map the relevant processes, or
the grid solvers can lead to instabilities in the solutions. However,
these are all known to science and have been studied in much detail.
It's exactly that so many different methods all give matching
solutions, which makes models such useful entities.

Of course, there are many other processes that need to be modeled as
well such as cloud formation, precipitation, chemical processes, solar
radiation, and so on and so on. Any time additional processes are
added, the model becomes more complex and thus verification and
validation take more and more time.
However to suggest that just because science may not fully understand
the full details of the many processes involved, that such models have
no predictive value seems 'nonsense' and allows one to reject the hard
work of thousands of scientists who are using and validating these
models.

On 4/17/07, Bill Hamilton <williamehamiltonjr@yahoo.com> wrote:
>
> Pim wrote
>
> That just pure nonsense. They [climate models] are hardly unreliable. In
> fact they are
> based on Navier Stokes equations, which are the basic equation of
> motion. Yes there are some parameters that require some tuning because
> they capture small scale effects not adequately captured by the grid.
>
> That's like saying that the models NASA uses to predict the path of the
> space shuttle are based on Newton's equations of motion. It's true, but
> there are many more factors, like the nonlinear drag of the atmosphere,
> gravitational anomalies, the effect of the moon's gravity, etc.
> Bill Hamilton
> William E. Hamilton, Jr., Ph.D.
> 248.652.4148 (home) 248.821.8156 (mobile)
> "...If God is for us, who is against us?" Rom 8:31
>
>
>
>
> ________________________________
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Received on Sun Apr 22 14:05:22 2007