Re: [asa] Creation Care

David Opderbeck wrote:

> It
> would be interesting to see how many authors and academic institutions
> are represented in those 900 articles, how many of those articles
> present truly new models or approaches to modeling, how extensively the
> models have been cross-checked through work in other disciplines, etc.
> It's not a trivial amount, I'm sure, but it doesn't approach the volume
> of work that's been done, say, on biological evolution.
>
I took a couple of undergraduate courses in numerical methods and a
graduate course. As best I can tell, as an outsider, the climate
models, at least the better ones involve solving differential equations
numerically (ie programs on computers) using the techniques of numerical
methods. One thing I learned is that for these computationally
intensive numerical modeling programs that one needs a really good
numerical analyst who can perform a very though error analysis, much
more knowledgeable and experiences than I ever was. My experience
working at a university for a while after graduation is that very few
scientists approached the numerical experts for help.

Climate and weather modeling also tends to be chaotic where small errors
in initial and boundary conditions can effect the result dramatically.
A frequently overlooked point however, is that each floating
point computation is only an approximations and introduce the same
kinds of effects that imprecision in constants... does.

As a programmer for 40 years I also learned that in any large complex
program there is no such thing as finding all the bugs. These models
likely have to run on a massively parallel processor complex, one more
source of error/bugs. Typically the models are validated against
historical data and when they match then people stop looking for bugs.
On the space shuttle NASA runs control programs on different hardware
and with programs independently produced.

Given the large economic impacts of many of the proposals, have any of
the models been totally independently programmed and validated during
development by experts in numerical analysis?

I was involved with some modeling of systems for a couple of years off
and on. In one case we were using a commercially available package to
get most of the results. If we got the results wrong then the down
stream result would have been for a fighter pilot to fly into a hill.
Thus I was concerned enough about the validity of our results that I
wrote a brute force program to check the results, at least for a few
tiny samples of the data.

> Where warming
> is different from ID/evolutionary science, I think, is in the extent of
> the conclusions that legitimately can be drawn from the science to date
> and in the breadth of the consensus. The volume of work done, the
> cross-disciplinarity, the correlation with predictions and observations,
> all are far more extensive in evolutionary science than in the science
> of climate change at this point in the respective research programs.

The other big difference is that, as far as I know, results in
evolutionary science do not depend so heavily upon computer modeling, at
least not to any where near the same extent as do studies of climate.
Researchers studying evolution can do physical modeling on small
populations and see what happens under various stimuli. Also of course
if the science backing evolution is wrong only a very few people are
affected, unlike with climate studies.

Am I saying that the scientists who do the modeling are incompetent? By
no means, my point is that numeric computer modeling is hard, very hard,
to get right. An example from another programming area, do you think
that Micro Soft likes to keep developers developing fixes rather than
working on new development?

It appears that the results could be very bad if nothing is done about
global warming however, doing something in the wrong way could also
impact people very negatively. My take is that most actions related to
global warming should also take Glenn's discussion on peak oil flow
seriously and attempt to do something about both problems. Improving
transportion systems has already been mentioned, but considerable energy
also goes into heating, cooling and lighting at least up here north of
the 49th parallel.

Dave Wallace

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Received on Sat Jan 20 13:01:24 2007