Friday, August 17, 2012

The Arrhenius Dilemma - Better Models, the Same Predictions


The Weasel on occasion makes posts out of his comments, and who is Eli but not to follow the lead of the local meat eater.

Over at Judy's confusatorium the denizens were complaining about how bad climate models are, Adam, the mathematician put on the harumphing regalia

Judith, this thread seems weird to me.

I am a mathematician. Statistics and probability as I know it is derived from basic principles, as all math is.

Only from deriving it from basic principles can we know that it works and is true.

I don’t see how we can have a discussion on model projections without it being mostly math. It seems to me that anything else is mostly heuristic (at best).

Am I wrong? And if so, can someone please educate me as to why I am wrong?
 Per chance wandering by it fell to Eli to point out why Adam was wrong.
Mostly because you have to estimate the forcing scenarios and those have physical, biological, economic and political drivers. Even if you had a perfect global model, you would have a wide range of possible outcomes, and some of those drivers are not controllable.
Of course the wise assed answer is that mathematics and statistics are derived from sets of half assed assumptions, but to be a bit more serious while you might learn more about how the Earth system works from better models, for the purposes of prediction, you wouldn't learn much. Thus the Arrhenius Dilemma

12 comments:

rab said...

Well, Eli, your post seems to have terminated the thread, so that's a win.

--rab

William Connolley said...

The question itself is odd: Adam is attempting to say that all discussion of model projections, just like all discussions of statistics, should be in mathematical form? So all discussion of economic projections, and economic statistics, should be largely mathematical?

If Adam looked outside of the blogs, at real peer-reviewed papers, he would find extensive maths-based discussions of climate models, and their projections. But all that stuff is too hard even for real blogs, let alone Curry's.

Another possible answer is that the models already embody the maths. What is needed is to translate this into other terms. Unless Adam is starting a campaign to move all decision making into maths'world.

Anonymous said...

Everyone knows that what Descartes (a mathematician) really meant was

"I calculate, therefore I am".

~@:>

Jeffrey Davis said...

I've read criticisms of climate models before and basically they boil down to: they don't give my answer.

"What would you do differently?" isn't answered.

Russell said...

The Weasel's invocation of "real blogs" in bunnyland raises an interesting semiotic question.

A lot of controversy arises when one dimensional models are adduced as proxies for complex three dimensional realities.

The same is true of political blogs that though lacking real scientific and mathematical dimensions, address complex policy questions.

One dimensional climate bloggerel, like Watts, elicits comments of such staggering self-similarity that three-dimensional mathmaticians might conjecture their origin in an alternative universe with a fractal scientific dimension of less than 1.

James Cliborn said...

Prof. Rabett, good observation; akin to Feynman's "...reality must take precedence over public relations..." Now, as luck would have it, there is no Wikipedia entry for "Arrhenius Dilemma." I think it would be just lovely if you would correct this omission! Best regards, Jim

Robin Johnson's Economics Web Page said...

Are these climate models just very complex perhaps even mangled analogies?
As Michael Tobis says all analogies are bonkers but they make for for more amusing reading.

Anonymous said...

"Everyone knows that what Descartes (a mathematician) really meant was

"I calculate, therefore I am".
"

Perhaps what he was trying to say was:

f(I)={i}
∴I∈{R}!



Bernard J. Hyphen-Anonymous XVII, Esq.

EliRabett said...

No, the models at all levels are based on physical principles and verifying observations, they are not analogies. GCMs are essentially weather models on steroids.

J Bowers said...

The UK Met Office issued an apology over the weekend for deciding to overrule their models that had predicted the thunderstorms we had. Will the GWPF be attacking the UKMO for their models being too good?

Anonymous said...

As a mathematician let me just say that the first rule of math is that it has nothing to do with the real world.

The second rule of math is that math cannot be shown to be consistent.

The fact that he wrote "Only from deriving it from basic principles can we know that it works and is true." proves that he is either not a mathematician, or a liar.

elspi

a_ray_in_dilbert_space said...

I am reminded of what John von Neuman said to a student who complained of lack of understanding:

"Young man, in math you do not understand things. You just get used to them."