Debating Superfreakonomics

Last month marked the release of Superfreakonomics, a sequel by economist Steven Levitt and journalist Stephen Dubner to the 2005 bestseller Freakonomics. The fanfare surrounding this prefix-enhanced release has been marred, however, by controversy surrounding a chapter on global warming. Starting with this entry on, the debate has drawn a few responses on the Freakonomics blog, but nothing has seemed to blunt the allegations that Dubner and Levitt wrote the chapter from a contrarian perspective without understanding even the fundamental principles of climate science, and as a result, what they've written is garbage.

Much of the writing back and forth has been quite heated, and being a student of mathematics I am averse to conflict. However, one response resonated with me a great deal, and as a case study of the arguments that can be made using only simple calculations, it's quite effective. The response in question comes from, and is titled "An Open Letter to Steve Levitt."

Written by fellow University of Chicago Professor Raymond T. Pierrehumbert, the letter takes Steve Levitt to task by harnessing the power of mathematics. After some opening remarks, Pierrehumbert sets the stage in the following way:

By now there have been many detailed dissections of everything that is wrong with the treatment of climate in Superfreakonomics , but what has been lost amidst all that extensive discussion is how really simple it would have been to get this stuff right. The problem wasn’t necessarily that you talked to the wrong experts or talked to too few of them. The problem was that you failed to do the most elementary thinking needed to see if what they were saying (or what you thought they were saying) in fact made any sense. If you were stupid, it wouldn’t be so bad to have messed up such elementary reasoning, but I don’t by any means think you are stupid. That makes the failure to do the thinking all the more disappointing. I will take Nathan Myhrvold’s claim about solar cells, which you quoted prominently in your book, as an example.

Myhrvold's claim in this context is essentially that using solar cells to fight global warming is not a good idea, because solar cells must be dark in order to absorb solar energy. However, only a fraction of that energy is converted into electricity, while the rest simply becomes waste heat that in turn will heat up the atmosphere.

Using nothing more than simple arithmetic, Pierrehumbert then tries to reason his way through such an argument to see if it makes any sense. As expected, it does not. My favorite part of the argument is the graphic that shows how many solar panels would be required to supply the world's electricity:

That black square in Saudi Arabia certainly doesn't look like it should make any significant contribution to the planet's heating, and indeed, Pierrehumbert uses mathematics to argue quite effectively that it wouldn't.

The letter is worth a read, not just for the strength of Pierrehumber's argument, but for the simple mathematics that gives his argument such strong support. Levitt offered a meek response in the comments (#47, I believe), which was then quickly rebutted. Since then, all's been quiet.

Of course, Levitt and Dubner may think that the math is on their side - since I haven't read the chapter in question, I can't comment. But the arguments put forth by Pierrehumbert are quite compelling, due in no small part to the simple calculations he performs. There's no doubt that mathematics can be used both for good and for evil, but Pierrehumbert, like Spider Man, seems to understand that with great power comes great responsibility.

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