A Friendly Bet on Global Warming
- by J. Scott Armstrong
In 2007, my attention was drawn to former Vice President Al Gore’s concerns about global warming. Having spent five decades studying the science of forecasting, I decided to examine the basis for the forecasts of global warming. I was unable to find a single scientific forecast to support the claim that the Earth was becoming dangerously warmer or colder. Instead, I found that some scientists were using improper forecasting methods to make forecasts.
I alerted Mr. Gore to this fact and suggested that they cooperate in a validation test of dangerous global warming forecasts. I suggested a 10-year bet for which I would forecast no long-term trend in climate, while Mr. Gore could chose forecasts from any climate model.
After a series of emails, Mr. Gore declined, apparently sticking with his claim that no time could be devoted to further study because we were near a “tipping point,” a position backed by James Hansen of NASA. I claimed that nothing new was happening, so there was neither cause for alarm nor need for government action.
I nevertheless determined to pursue the proposed forecasting test. By using the commonly adopted U.N. Intergovernmental Panel on Climate Change forecast—3 degrees C of warming per century—to represent Mr. Gore’s position, theclimatebet.com has tracked the Armstrong-Gore “bet” with monthly updates.
Mr. Gore should be pleased to find that his grave concerns about a “tipping point” have turned out to be unfounded. As shown on theclimatebet.com, my forecasts have been more accurate than Mr. Gore’s for 40 of the 60 months to date and for four of the five years. In fact, the latest global temperature is exactly where it was at the beginning of the “bet.”
I am not surprised. With some minor exceptions, my forecast was consistent with evidence-based forecasting principles. In contrast, the IPCC’s forecasting procedures have been found to violate 72 of the 89 relevant principles.
When I proposed the bet, I expected to have somewhat less than a 70 percent chance of winning, given the natural variation in global mean temperatures for a 10-year period. In light of the results to date, I expect an even better chance of winning, but, as Yogi Berra said, “It’s not over till it’s over.” Furthermore, policy decisions will require validations testing for hundreds of years, not for just one decade. At the time of writing, there has been no trend in global mean temperatures for 16 years.