This was new to me when it
popped up at WUWT. But apparently is has already been around for a week or so, at
Fox News and
The Australian. Economists Scott Armstrong and Kesten Green, who regard themselves (pompously) as authorities on forecasting, made a splash ten years ago when they
made a challenge of a bet with Al Gore that their forecast of global temperature, based on no change, would be better over the next ten years than his. They even
set up a website, to track his response, and presumably track the bet. And they got a good run in the conservative media at the time.
Gore never showed any interest - he just said that he doesn't bet. So it was empty noise. However, for some strange reason, there is now a volley of fantasy articles, attributing a bet to Gore (in which he had no say) and declaring him the loser. The terms of the bet are exceedingly arcane. Since they have to make up some warming forecast, they picked an "IPCC" forecast of 0.3°C warming for the decade.
The first thing to say is that the IPCC made no such forecast. They did, in the AR4 SPM that came out at abaout that time,
say this:
For the next two decades, a warming of about 0.2°C per decade is projected for a range of SRES emission scenarios.
And it was for surface temperature, not the troposphere measure that Armstrong/Green decided on.
But that itself turns out oddly. They nominate UAH as a measure, which actually has a slightly higher trend over the period than surface measures. Here is the plot
And they are betting with zero trend (blue). The actual was more than double the "IPCC trend". They lose by a mile. But in the WUWT article, at least, they say the OLS trend for the period is 1.53°C/Century. But they prefer a measure they make up called Least Absolute Deviation (LAD).
Well, they would, wouldn't they, because they say that comes out to 1.14°C/Century, and on that basis they declare themselves the winner (since they have pinned Gore with the "IPCC" 3 C/century. Of course it is 2, not 3, so even on that basis they lose. But since they seem to have miscalculated the OLS trend by a factor of 3, I have no faith in their LAD calculation.
On the plot, I've marked a line with slope 1.14°C/century in green, and the Armstrong/Green zero forecast in blue. They all, as fitted lines should, pass through the mean of x and y. See if you think the "LAD" line (1.14) is a better fit. Or whether the no trend forecast is the winner.
Scott Armstrong is a professor of marketing.
Kesten Green is a lecturer in Commerce. Neither seems to know much about what the IPCC actually says. And they seem pretty weak in statistics.