DeLong is right, what Levitt said is “not economics.” Rather, it’s a historical claim. Maybe it’s right, maybe it’s wrong, but DeLong can’t trump it by citing a tautology from microeconomics. I am sure that Levitt would concede the narrow point, that if governments around the world instituted a massive carbon tax, and enforced it with draconian penalties for evasion, then global emissions would indeed fall quickly.

But one of Levitt’s main points is that governments around the world are not going to do this, that it is naive to expect them to sacrifice their own economies when (in Levitt’s opinion) the climate science is not nearly certain enough to justify this painful step. Levitt is making a prediction–based on his interpretation of history–that if manmade global warming really does require drastic measures in the next few decades, that the response will involve various forms of geoengineering, which (Levitt predicts) will cost a tiny fraction of what the carbon mitigation proposals would require. To repeat, I’m not saying I necessarily endorse Levitt’s glib proclamations on these points, but DeLong is wrong for dismissing them as somehow “not economics.”

# posted by Bob Murphy @ 12:01 PM