I wasn’t aware that Scott Armstrong – one of the guru’s of forecasting – and Al Gore almost had a bet. The bet goes something like this:
In 2007, University of Pennsylvania Professor J. Scott Armstrong’s attention was drawn to former VP Gore’s concerns about global warming. Having spent five decades studying the science of forecasting, Armstrong decided to examine the basis for the forecasts of global warming. He was unable to find a single scientific forecast to support the claim that the Earth was becoming dangerously warmer or colder.
Instead, he found that some scientists were using improper forecasting methods to make forecasts. Professor Armstrong alerted Mr. Gore to this fact and suggested that they cooperate in a validation test of dangerous global warming forecasts. He suggested a 10-year bet for which he would forecast no long-term trend in climate, while Mr. Gore could chose forecasts from any climate model.
Before anyone gets too excited let’s unpack a couple of those terms, especially “scientific forecast” and “improper forecasting methods”. Kesten Green and Scott Armstrong have a paper that evaluates the IPCC forecasts against 140 accepted principles of forecasting and the IPCC methodology comes up short.
To provide forecasts of climate change that are useful for policy-making, one would need to forecast (1) global temperature, (2) the effects of any temperature changes, (3) the effects of alternative policies, and (4) whether the best policy would be successfully implemented. Proper forecasts of all four are necessary for rational policy making.
The IPCC Report was regarded as providing the most credible long-term forecasts of global average temperatures by 31 of the 51 scientists and others involved in forecasting climate change who responded to our survey. We found no references to the primary sources of information on forecasting methods despite the fact these are easily available in books, articles, and websites. In our audit of Chapter 8 of the IPCC’s WG1 Report, we found enough information to make judgments on 89 out of a total of 140 forecasting principles. The forecasting procedures that were described violated 72 principles. Many of the violations were, by themselves, critical.
I have seen Kesten Green present this paper and given what we now know about the IPCC it doesn’t surprise me. But this part of the argument, I think, is weak. The argument here falls into an area where the opinions of Green-Armstrong conflict with the opinions of the IPCC forecasters and the area where the art and science of forecasting overlap. I’m not saying Green-Armstrong are wrong just that I’m not entirely convinced that it is correct. But this is the basis for the terms “improper forecasting methods” and not a single “scientific forecast”. Okay – the next bit is much more interesting.
Kesten Green, Scott Armstrong and Willie Soon published a paper that set out a “no-change” benchmark forecast of global temperatures. I have seen Kesten Green present this paper too – it is much more convincing than the previous paper.
Global mean temperatures have been remarkably stable over policy-relevant horizons. The benchmark forecast is that the global mean temperature for each year for the rest of this century will be within 0.5C of the 2008 ?gure.
There is little room for improving the accuracy of forecasts from our benchmark model. In fact, it is questionable whether practical bene?ts could be gained by obtaining perfect forecasts. While the Hadley temperature data in Fig. 2 drifts upwards over the last century or so, the longer series in Fig. 1 shows that such trends can occur naturally over long periods before reversing. Moreover, there is some concern that the upward trend observed over the last century and half might be at least in part an artifact of measurement errors rather than a genuine global warming (McKitrick & Michaels, 2007). Even if one accepts the Hadley data as a fair representation of temperature history, our analysis shows that errors from the benchmark forecasts would have been so small that decision makers who had assumed that temperatures would not change would have had no reason for regret.
So that paper forms the basis for the proposed bet. Indeed the paper discusses the famous Julian Simon – Paul Ehrlich bet. As it turns out Al Gore did not accept the bet.
Nonetheless the question arises, how would the bet be going?
Of the first 60 months of the 120 month (10 year) Climate Bet, Scott Armstrong’s naive model forecast* of no change in global average temperatures has been closer to the actual temperature than Al Gore’s IPCC-orignated 3°C per century warming forecast for 40 months.
Scott Armstrong is confident of winning.
When he proposed the bet, Professor Armstrong expected to have a somewhat less than 70% chance of winning given the natural variation in global mean temperatures for a ten-year period. In light of the results to date, he expects an even better chance of winning, but as Yogi Berra said, “It’s not over till it’s over.”
Something to watch with interest.