Pascal’s Green Wager

Earlier this month, Paul Krugman took to the pages of the New York Times Sunday magazine to urge the building of a “Green Economy.” Along the way, he wrote this:

Finally and most important is the matter of uncertainty. We’re uncertain about the magnitude of climate change, which is inevitable, because we’re talking about reaching levels of carbon dioxide in the atmosphere not seen in millions of years. The recent doubling of many modelers’ predictions for 2100 is itself an illustration of the scope of that uncertainty; who knows what revisions may occur in the years ahead. Beyond that, nobody really knows how much damage would result from temperature rises of the kind now considered likely.

You might think that this uncertainty weakens the case for action, but it actually strengthens it. As Harvard’s Martin Weitzman has argued in several influential papers, if there is a significant chance of utter catastrophe, that chance—rather than what is most likely to happen—should dominate cost-benefit calculations. And utter catastrophe does look like a realistic possibility, even if it is not the most likely outcome.

Weitzman argues—and I agree—that this risk of catastrophe, rather than the details of cost-benefit calculations, makes the most powerful case for strong climate policy. Current projections of global warming in the absence of action are just too close to the kinds of numbers associated with doomsday scenarios. It would be irresponsible—it’s tempting to say criminally irresponsible—not to step back from what could all too easily turn out to be the edge of a cliff.

Weitzman’s actual work on this is more complex and intelligent than a newspaper can reasonably be expected to make clear, but as presented by Krugman, what we are presented with in environmentalism is a straightforward, old-school version of Pascal’s Wager.

The persuasive way to read Pascal’s original is as a performance argument and a prayer, but, taken as a flat set of logical possibilities, it has an answer in the extremely unlikely possibility that God rewards disbelief or that God punishes belief. The argument imagines only one edge of the probability curve exists.

Which is, of course, what Krugman’s environmental version does. But, even more, Pascal’s argument needs infinity to make itself run: The infinitely good consequences of belief, and infinitely bad consequences of disbelief, are necessary to overcome the minutely small possibilities it says it answers. And this, of course, is what Krugman doesn’t have, no matter how much he mutters about “doomsday scenarios.”

Think of it this way: The problem isn’t that Global Warming is a religion rather than a science; the problem is that it’s an incompetent religion.