Armstrong has just offered Al Gore a $US20,000 ($23,000) bet that the Intergovernmental Panel on Climate Change temperature forecasts are wrong.

This passage intrigued me. What counts as “being wrong”? Here’s what I learned at the bet’s official website:

Scott Armstrong of the Wharton School challenges Al Gore $20,000 that he will be able to make more accurate forecasts of annual mean temperatures than those that can be produced by climate models. Scott Armstrong’s forecasts will be based on the naive (no-change) model; that is, the forecasts would be the same as the most recent year prior to the forecasts

The charity designated by the winner will receive the total value in the fund when the official award is made at the annual International Symposium on Forecasting in 2018. (emphasis mine)

If I understand this bet correctly, Armstrong wins if 49% of the global warming predicted by Gore occurs. So while the bet is far from rigged, it’s less than ideal. If the issue is whether global warming will happen at all, the obvious bet is “if annual mean temperature goes up, you win; if it goes down, I win.”

Or if you prefer a smarter bet: If it goes up by more than 2 standard deviations, you win; if it goes down by more than 2 standard deviations, I win; otherwise the bet is off.

Even so, I’m impressed; as far as I can tell, no climate change skeptic has done more to put his money where his mouth is than Armstrong. My question for Armstrong: Will you bet with anyone other than Gore? Last time I checked, there was a queue of believers in climate change who couldn’t find anyone to bet with.