POL Freeman Dyson

[David C Kifer]

And this Renaissance Man, who has been prescient in many spheres,
among them space travel and genetic diversity, who has written nine
provocative books of his own and inspired dozens by others, is today
known, too, as a scientific heretic, chiefly for disagreeing with the
conventional wisdom on global warming. Or, as he puts it, "all the
fluff about global warming."
The "fluff," Prof. Dyson explains, comes from climate-change
models that predict all manner of catastrophe. The models count for
naught as predictive tools.
"I have studied their climate models and know what they can do,"
Prof. Dyson says. "The models solve the equations of fluid dynamics
and do a very good job of describing the fluid motions of the
atmosphere and the oceans. They do a very poor job of describing the
clouds, the dust, the chemistry and the biology of fields, farms and
forests. They do not begin to describe the real world that we live in."
Prof. Dyson explains that the many components of climate models
are divorced from first principles and are "parameterized" --
incorporated by reference to their measured effects.
"They are full of fudge factors that are fitted to the existing
climate, so the models more or less agree with the observed data. But
there is no reason to believe that the same fudge factors would give
the right behaviour in a world with different chemistry, for example
in a world with increased CO2 in the atmosphere," he states.
Prof. Dyson learned about the pitfalls of modelling early in his
career, in 1953, and from good authority: physicist Enrico Fermi, who
had built the first nuclear reactor in 1942. The young Prof. Dyson and
his team of graduate students and post-docs had proudly developed what
seemed like a remarkably reliable model of subatomic behaviour that
corresponded with Fermi's actual measurements. To Prof. Dyson's
dismay, Fermi quickly dismissed his model.
"In desperation, I asked Fermi whether he was not impressed by the
agreement between our calculated numbers and his measured numbers. He
replied, 'How many arbitrary parameters did you use for your
calculations?' I thought for a moment about our cut-off procedures and
said, 'Four.' He said, 'I remember my friend Johnny von Neumann [the
co-creator of game theory] used to say, with four parameters I can fit
an elephant, and with five I can make him wiggle his trunk.' With
that, the conversation was over."
Prof. Dyson soon abandoned this line of inquiry. Only years later,
after Fermi's death, did new developments in science confirm that the
impressive agreement between Prof. Dyson's model and Fermi's
measurements was bogus, and that Prof. Dyson and his students had been
spared years of grief by Fermi's wise dismissal of his speculative
model. Although it seemed elegant, it was no foundation upon which to
base sound science.
-- LawrenceSolomon, Fighting climate 'fluff', Financial Post, April
05, 2007
http://www.canada.com/nationalpost/news/story.html?id=985641c9-8594-43c2-802d-947d65555e8e

--
Dave
"Tam multi libri, tam breve tempus!"
(Et brevis pecunia.) [Et breve spatium.]