modeling

Modeling, Science, and Physics Envy

Climate Skeptic notes the similarity of climate models and macroeconometric models:

The climate modeling approach is so similar to that used by the CEA to score the stimulus that there is even a climate equivalent to the multiplier found in macro-economic models. In climate models, small amounts of warming from man-made CO2 are multiplied many-fold to catastrophic levels by hypothetical positive feedbacks, in the same way that the first-order effects of government spending are multiplied in Keynesian economic models. In both cases, while these multipliers are the single most important drivers of the models’ results, they also tend to be the most controversial assumptions. In an odd parallel, you can find both stimulus and climate debates arguing whether their multiplier is above or below one.

Here is my take, from “Modeling Is Not Science“:

The principal lesson to be drawn from the history of massive government programs is that those who were skeptical of those programs were entirely justified in their skepticism. Informed, articulate skepticism of the kind I counsel here is the best weapon — perhaps the only effective one — in the fight to defend what remains of liberty and property against the depredations of massive government programs.

Skepticism often is met with the claim that such-and-such a model is the “best available” on a subject. But the “best available” model — even if it is the best available one — may be terrible indeed. Relying on the “best available” model for the sake of government action is like sending an army into battle — and likely to defeat — on the basis of rumors about the enemy’s position and strength.

With respect to the economy and the climate, there are too many rumor-mongers (“scientists” with an agenda), too many gullible and compliant generals (politicians), and far too many soldiers available as cannon-fodder (the paying public).

Scientists and politicians who stand by models of unfathomably complex processes are guilty of physics envy, at best, and fraud, at worst.

Physics Envy

Max Borders offers a critique of economic modeling, in which he observes that

a scientist’s model, while useful in limited circumstances, is little better than a crystal ball for predicting big phenomena like markets and climate. It is an offshoot of what F. A. Hayek called the “pretence of knowledge.” In other words, modeling is a form of scientism, which is “decidedly unscientific in the true sense of the word, since it involves a mechanical and uncritical application of habits of thought to fields different from those in which they have been formed.” (“The Myth of the Model,” The Freeman, June 10, 2010, volume 60, issue 5)

I’ve said a lot (e.g., here, here, here, here, here, here, here, and here) about modeling, economics, the social sciences in general, and the pseudo-science of climatology.

Models of complex, dynamic systems — especially social systems — are manifestations of physics envy, a term used by Stephen Jay Gould. He describes it in The Mismeasure of Man (1981) as

the allure of numbers, the faith that rigorous measurement could guarantee irrefutable precision, and might mark the transition between subjective speculation and a true science as worthy as Newtonian physics.

But there’s more to science than mere numbers. Quoting, again, from The Mismeasure of Man:

Science is rooted in creative interpretation. Numbers suggest, constrain, and refute; they do not, by themselves, specify the content of scientific theories. Theories are built upon the interpretation of numbers, and interpreters are often trapped by their own rhetoric. They believe in their own objectivity, and fail to discern the prejudice that leads them to one interpretation among many consistent with their numbers.

Ironically, The Mismeasure of Man offers a strongly biased and even dishonest interpretation of numbers (among other things). When a leading critic of physics envy falls prey to it, you know that he’s on to something.