Sunday, February 20, 2011

Climate betting update for 2010

I had my annual friendly email exchange with betting partner/opponent, David Evans, several weeks back. Our bet:
We have three bet periods -10, 15, and 20 years - and two bets for each period - an even-odds bet and a 2:1 bet in David's favor. The even-odds bet centers around a temperature increase rate of 0.15C/decade with a 0.02 void margin on either side (bet voids if temps increase between .13 and .17C/decade). The 2:1 bet centers on 0.1C/decade with a .01 void margin. Even-odds bets are for $1,000 each, and the 2:1 bets increase over time, with me betting $1,000, $2,000 and $3,000, and David betting half that. My exposure is $9,000; his is $6,000.
We use the NASA GISS dataset, and the baseline is the five-year average for 2007 (.55C above the long-term average), compared to five year averages of each of the three bet periods. Years 2010 through 2014 won't "count" in the sense of not being measured in the five year averages, but they will give a sense of who's winning.

So who's winning? Interestingly, David and I both focused on the news that was bad for our own side. In 2010, the global average temp was a record .63C above the long-term, an increase of .08C in just three years from 2007's multi-year average, and a pace that far exceeds what I need to win all of the bets. That's the perspective David took.

By contrast, I compared five-year averages: we're now able to calculate the five-year average centered on 2008, and it's only .01C above 2007's multi-year average. The reason for the small change is that the only difference between the averages is that 2007's average included the record year 2005, while 2008's average dropped the record year 2005 and replaced it with the record year 2010. At a .01C annual increase rate, I will lose half of my bets and void the other half.

Looking forward to this time next year, our perspectives might shift again, assuming 2011 plays out as another warm year but La Nina-cooled from 2010. The five year average for 2009 will eliminate 2006, which was only typical and cooler than 2005, and replace it with 2011. Any 2011 temperature above .58C should put me in good shape for the five-year average, even if it's not as blistering as 2010. So we'll see.

Meanwhile, James Annan continues his too-easy path to climate betting riches with Russian skeptics. I've been meaning to reach his betting opponents to see if they agree that their goose is cooked, and if not, whether they'd like to double down.

UPDATE: The skewed prediction-market bet that exaggerated the short-term warming anticipated by the IPCC turned out to be insufficiently skewed, and the "Al Gore side" won the bet. The website promoting the bet on behalf of denialist Scott Armstrong has been mysteriously silent about this development, talking only about a longer, proposed bet that's still artificially skewed by lying about the predicted short-term warming. And just in case that bet disappears down the memory hole, here's how describes it:

“Now, assume that Armstrong and Gore made a gentleman‟s bet (no money) and that the ten years of the bet started on January 1, 2008. Armstrong‟s forecast was that there would be no change in global mean temperature over the next ten years. Gore did not specify a method or a forecast. Nor did searches of his book or the Internet reveal any quantitative forecasts or any methodology that he relied on. He did, however, imply that the global mean temperature would increase at a rapid rate – presumably at least as great as the IPCC‟s 1992 projection of 0.03°C-per-year (NOTE: untrue statement, no short term IPCC prediction was made in 1992, and later reviews made lower decadal predictions - ed). Thus, the IPCC‟s 1992 projection is used as Gore‟s forecast.”
Finally, the small bet I've got with Joe Romm on whether 90% of Arctic sea ice will disappear by 2020 (with me taking the cold side) chugs along. Joe does have a chart here showing that recent decline rates, projected linearly, would have him winning. I'm not so sure, although I'm also less sure of my side than I was when I took the bet.


  1. If Eli were James, he would worry about the Russkis actually paying off.

  2. Yeah, that's the problem with the big money bets, and the little money bets are too easy for the unserious to do.

    OTOH, James has very little risk.


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