Saturday, April 24, 2010

Minor myths: the Armstrong-Gore climate "bet"

In 2007, Scott Armstrong proposed a ten-year wager to Al Gore -- no warming (Armstrong's prediction) vs. warming (Gore's prediction). Gore declined, saying he doesn't gamble. And there was no wager, so that was the end of it. Kidding! What happened was that it became a minor myth picked up by the likes of Intrade and followed on Denialists like to claim that Gore is "losing the bet," a claim that interested me because of the number of lies packed into a simple declarative sentence. I will delve into this at greater length later, but here is a thumbnail sketch of the fallacies involved that sentence:

1. There was no bet, as Gore declined the offer.
2. Gore hasn't given an estimate for future warming, so the denialists chose 0.03C per year, which they claim is the "linear trend" predicted by the third IPCC report.
3. The trend predicted by the IPCC is not linear.
4. The trend is not 0.03C per year. The third IPCC report predicted a warming trend of 0.15C-0.30C/decade over the next several decades. Not only does the "bet" ignore the time frame (see #6), but rather than chose the middle of the range, the deniers have chosen to pretend the higher end of the estimate, the maximum possible, is the "projection" of the IPCC report.
5. The "bet" was proposed in 2007, when the fourth IPCC report came out -- but the denialists went to the out-of-date report for their estimates of warming. (The fourth report does not change things much -- it estimates warming of about 0.2C in coming decades.
6. It's a ten-year bet, yet denialists are tracking meaningless figures like who "won" the year or even who "won" the month (of course, short-term variations caused by solar activity, ENSO, and the like make it impossible to translate a prediction of 0.2C/decade averaged over several decades to a prediction for one decade, let alone a single month or year. Scott Armstrong himself has warned the denialists that this makes no sense, but they persist.
7. Even with these cherry-picked conditions, Gore has "won" six of the last seven months. Intrade gives him a 75% chance to "win" the year. Coincidentally, stopped posting updates on the status of the "bet" . . . exactly six months ago.


  1. You also realize that Armstrong's claim was no warming - something that seems almost ludicrous considering that the trend over the past 150 years has been 0.17C/decade. One of the biggest problems with the AGW hypothesis is that wants to attribute past warming to nature but most future warming to man with a trend that is fairly stable over the long term. If all that had happened was a continuation of the same trend that has been in place since the 1800's Armstrong should lose handily.
    I fully expect that the future will bring periods of warmer as well as cooler temperatures - in cycles following the general trend that has likely been occuring since the end of the little ice age. When you can demonstrate a trend longer than half a century with more than a 0.17C/decade increase I will be happy to concede the debate. In the meant time all you have is deeply flawed computer models and the natural variablity of weather and the planet.

  2. They have started posting again: seems like a fair bet to me. What would you propose as an alternative?

  3. What would you propose as an alternative?

    I discussed this here:

    In brief:

    * Use something closer to the actual model predictions, like 0.2C/decade vs no warming.
    * Use a rolling average (the 11-year average would be optimal), not a month-to-month anomaly . . . that's nuts.

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  6. I found this in the AR4 (2007) Synthesis Report "Since the IPCC’s first report in 1990, assessed projections have suggested global averaged temperature increases between about 0.15 and 0.3°C per decade from 1990 to 2005. This can now be compared with observed values of about 0.2°C per decade, strengthening confidence in near-term projections. {WGI 1.2, 3.2} "
    So though not 2001 but 2007, your argument is still valid!

  7. I have a Twitter thread below, discussing some of the evidence rebutting Armstrong's prediction. It turns out there was about as much (or more) observed warming than the warming trend Armstrong made up and attributed to the IPCC: