Betting on Climate Change

It's time to put up or shut up


Reporting on the climate change debate is not for sissies. For example, one line in an article I wrote back in November discussing the Arctic Climate Impact Assessment triggered a furor among climate change bloggers. I reported a bet by MIT climatologist Richard Lindzen that in 20 years global average temperatures would be lower than they are now. This "bet" circulated as blogfodder in climatological circles. *

Subsequently, James Annan, who works with the Data Assimilation group at the Frontier Research Center for Global Change, noted the "bet" and emailed Lindzen about setting up an actual bet. Annan and Lindzen engaged in an exchange but were unable to settle on a mutually acceptable bet. Annan summarizes their exchange on his blog, claiming that Lindzen would take only 50 to 1 odds on global temperatures in 20 years being lower than they are now.

Obviously, I feel responsible for getting this whole thing started. I contacted Lindzen, who insisted that I had misquoted him. Given the rancor that sometimes accompanies the debate over climate change I try to be very careful about what I report. I've looked again at the notes of my phone interview with Lindzen and they say what I reported in my November column. At this point, I can only conclude that when I was taking down my notes during our conversation, I somehow misheard or misunderstood Lindzen. My mistake.

So, for the record, what does Lindzen actually believe? This is how Lindzen responded to Annan: "The quote [at Reason Online] was out of context. I think the odds are about 50-50. I said that if anyone were willing to give warming much higher odds than that, I would be tempted to take the bet." Lindzen and Annan subsequently haggled a bit over what would be a fair bet. From Lindzen's point of view, any such bet would be between people like Annan, who are convinced by climate model projections that average global temperatures should be increasing about 0.3C per decade, and people who think it's even odds that temperatures will be lower than they are now in 20 years.

Setting aside the bet that global temperatures will be lower in 20 years, Lindzen offered Annan an alternative bet. If the temperature change were less than 0.2C, he would win. If the temperature change were between 0.2C and 0.4C the bet would be off. And if the temperature change were 0.4 or greater, Annan would win. He would take 2 to 1 odds. After all, Lindzen is on record as saying that global average temperatures could rise by 1 degree Celsius over the next century. In contrast, climate model projections predict a warming of 1.4 to 5.8 degrees Celsius by 2100, though a new study in January suggested global warming could be "Twice as Bad as Previously Thought," with an upper projection of average global temperatures reaching 11 degrees Celsius.

Annan then countered with a bet pegged to some agreed upon average temperature in 20 years with payouts based on how many hundredths of a degree Celsius the loser was from the agreed upon temperature. Lindzen responded by skeptically asking how one would accurately measure hundredths of a degree Celsius on a global level. Their negotiations apparently ended there and, at least on the part of Annan, the blogging began.

Still, betting on the outcome of scientific controversies is a good idea. James Annan explicitly cited the famous bet between Paul Ehrlich and Julian Simon about the future prices of natural resources, saying that he believed that "such wagers have an important role to play in clarifying the issues involved in prediction and uncertainty." Ehrlich, convinced that non-renewable resources were becoming increasingly scarce, bet that the prices of his handpicked basket of five metals would increase over the next ten years. Ten years later Ehrlich sent Simon a check for $576.07. In other words, instead of rising as predicted by Ehrlich, the prices of the five metals selected by Ehrlich had fallen by more than half.

Organizing such bets is similar to the concept of idea futures markets. Instead of trading weather futures, one might be able to trade climate futures. In the meantime, the Long Bets Foundation is taking bets on a variety of future predictions. At the Long Bets Web site, people propose bets with real money held in escrow to be paid out to a selected charity when the bet is won. Mark Bahner, an environmental engineer and evident climate catastrophe skeptic, is betting that novelist Michael Crichton's projection of future global temperatures are more accurate than those of the United Nations' Intergovernmental Panel on Climate Change (IPCC). Bahner's bet is open only to members of the IPCC. If Annan works on IPCC reports, he might want to take Bahner's action.

However, with all due respect to Annan and Bahner, it would be far more interesting and valuable to the climate debate if major figures in the climate change debate would negotiate a bet about the future of global temperature trends. James Hansen or Stephen Schneider could represent those worried about dangerous global warming, and John Christy or Patrick Michaels could pony up for the skeptics. It's time to put up or shut up.

* This article has been corrected. An erroneous reference to William M Connolley has been removed. (Return to the corrected portion.)