While sitting there, I was reminded of the speeches that Alan Greenspan gave a few years ago about the risks of deflation. It wasn’t the most likely outcome, he said, but the consequences of it could be so bad that policy makers had to take steps to prevent it. Focusing attention on this point -the catastrophic risks of climate change- is Sir Nicholas’s biggest accomplishment, whatever you think of his math.
As Mr. Weitzman puts it, the Stern Review is “right for the wrong reasons.”
Even its critics seem open to this idea. When Mr. Nordhaus and Sir Nicholas were exchanging e-mail messages before the debate -to their credit, some academics keep their arguments from becoming personal- Mr. Nordhaus sent a note that summed up his view. “I think it’s a great study, but it’s 50 years ahead of its time,” he recalled writing. “Since everybody else is 50 years behind the times, if you average the two, you might come out just right.”