Tuesday, June 28, 2005

Realclimate betting article wash-up.

Well, the comments on my article have been closed. 124 posts seems to be a record, so at least it seemed to generate some interest, even if it was more heat than light. Maybe I will have the opportunity to contribute with some of my more mainstream scientific reseach in the future.

Although I did post a couple of replies in the comments, I tried to avoid getting drawn into answering every minor detail there, as the blog format doesn't really lend itself to sensible multi-party debate. Instead, here's a summary of some of the points raised.

Firstly, I've still not found a sceptic who is prepared to bet against continued warming at the IPCC-predicted 0.15C/decade. Chip Knappenburger explicitly endorsed it, which was quite a contrast with his recent email bluster about how the recent warming was anomalous and liable to be reversed (in connection with this blog post). Neither he nor anyone else could come up with any concrete examples of the alarmism that supposedly infests mainstream climate science.

I don't think Joel Kuni's idea quite adds up in the form he presented it, but certainly a long term prediction designed to test the climate science would have to be conditional on GHGs. There are standard approaches to this sort of issue, so it is not an insurmountable problem. As far as the correlation between GHGs and temperature goes, recent history already passes his r2>0.5 test with flying colours - the Mauna Loa CO2 data vs GISTEMP from 1961-2004 gets r2=0.76, and I'm sure that the Vostok ice core data must be in the same ballpark over ~400,000 years or more (a quick google finds multiple references to the strong correlation but no hard numbers and I can't be bothered doing it myself).

Mark Bahner keeps on ranting about how the IPCC "predictions" for GHGs are wrong. He seems to confuse the TAR with a paper by Wigley and Raper which appeared around the same time. (His error must be deliberate misrepresentation, since I've pointed out this mistake several times. At least Chip Knappendale had the honesty to admit his mistake when I called him on the same trick.) W&R make the assumption that the SRES scenarios define a probabilistic distribution of future emissions in the absence of regulatory action, but the IPCC does not. I have no problem with W&R making that assumption if they think it is appropriate, but it is clearly their own assumption, explicitly disowned in the SRES. In any case, since some sort of political action is well-nigh inevitable, W&R's premise will be falsified and their "prediction" will not be applicable to the real world. It's a "what would happen if we take no action", not a "this is what we think will happen". The situation is rather different from forecasting the weather, in that we actually get to choose (at least, influence) the direction that society takes.

Last, and least, the "junkscience bet". I'm disappointed that anyone would be taken in by this sort of nonsense, since it was patently obvious that Milloy was looking for excuses rather than a deal right from the outset. For starters, he props up the tired old straw man of the "median IPCC estimate"of 1C warming from 1990 to 2025 (which is only to be found in his imagination, not the IPCC TAR itself). Then he brings up the classic red herring of errors in measuring absolute temperature, which as Gavin noted is irrelevant to the question of temperature anomalies. Then, just in case there is still a chance of a bet, he says that he won't trust the measurements anyway. All he's offered is a bunch of snivelling excuses, but his fans all lap it up anyway. I just hope that at least some of them have the honesty to feel a little sheepish about it.


Brian said...

124 posts, and you only managed to find one person willing bet $25, and that one took a lot of pulling teeth. Not much chance to make money off of this.

I don't think Milloy is actually offering a bet. He says, "What do you think? If you believe you can work out a fair wager for climate over 20 years, drop us a line. Workable entries may be published."

IOW, he's just offering to publish a "fair wager", not take one up.

Anonymous said...

Regarding Mr. Bahner.

I've explained the difference between predictions and the TAR scenario analysis to Mr. Bahner many times over on Brad Delong's site. I don't think it really makes a difference whether it's willful ignorance or deliberate deception:



James Annan said...


I agree, Milloy won't bet but probably thought he'd better chuck out some distraction cos of Ron Bailey's "put up or shut up" article.


That was interesting. I had naively thought that perhaps Bahner was a newbie who was confused or misled rather than just stubbornly stupid. But it seems he's been pumping out this crap for years. He seems to have little staying power compared to the professional trolls though.

Anonymous said...

(Here is another person in your institution who is interested in
uncertainty of climate prediction -- though I do not work on it
but just want to use such information.)

I missed the chance to comment on your posting at RealClimate
and then arrived here.

I hesitated to write there, mainly because I really do not understand
betting or ideas futures markets and I actually am not interested in them.
What I wanted to mention is my understanding about Lindzen's attitude.
But again, since you directly contacted him and I did not, probably
you know better about what he thinks than I do.

But anyway I would like to tell you what I thought.

===== Begin comment (originally intended to appear in RealClimate) =====
I never bet, therefore I do not actually comprehend the psychology
of a better (bet-er, I mean).
But, in my opinion, the claim that rational persons must bet at a rate
consistent with their subjective statistical expectations is valid
only when we can (potentially) make the same bet many times, that is,
when practically independent events occur at practically the same probability.
When one can bet only once, or only once in 20 or 30 years, one can be
either more conservative or more speculative without losing practical
rationality. (This is just my belief and you need not agree.)

I do not think there is a consensus among so-called global warming skeptics
comparable to the consensus formed in IPCC (2001). They are not absolute
skeptics who consider any claim equally doubtful. But they are
usually less consensus-seeking than the majority of scientists.
I do not mean those people who are not really skeptics but believers of
a certain leader. I mean original thinkers among so-called skeptics.

I have not communicated with Lindzen after he came out as a global
warming skeptic, thus I am not absolutely sure, but I think that
it is inappropriate to call his position as 50-50 probability to
warming or cooling. If Stephen Schneider at
ctions.html is correct,
Lindzen is the Expert 5 in the survey of subjective judgements
by Morgan and Keith (1995, Environmental Science and Technology 29:468-476),
who said that the global mean temperature response to CO2 doubling would be
0.3 +/- 0.2 K. Zero is 1.5 times standard deviation away from the average.
Expectation of small but positive CO2-greenhouse warming is consistent with
his claims of strong negative feedbacks by upper tropospheric water vapor
or cirrus clouds which would lose sense without initial warming in the
global tropics. I do not know his expectation about the 20-year trend,
but it seems reasonable to assume some fraction of the above value.
I take one quarter of CO2-doubling response which would be 0.075 +/- 0.05 K.
I guess that the rate of fair bet for a person who holds such view would
be about 1:50 if normal distribution is assumed. (Maybe I am misunderstanding
statistics, but anyway that is certainly not around 1:1.)

There is also uncertainty about determining the outcome of the trend of
global mean temperature after 20 years. It may be biased accidentally,
or may be biased subconsciously by those who explicitly or implicitly
participate in the bet. To those people who thinks the absolute value
of the outcome is small, the effect of uncertainty would seem serious.
If he takes some safety margin, his choice is likely to shift somewhat.

There may exist other so-called skeptics who view differently.
Some may think that climate may vary wildly even without human intervention.
I know a past Japanese example, but I take Michael Crichton's "State of Fear"
as an example familiar to many readers here. His MIT professor claims
that climate changes chaotically, and the author himself shows a guess of
the 100-year trend as +0.8+something deg. C. If these represent a consistent
position (though it need not be true), the position would generally agree
with Lindzen about the mean but disagree about the standard deviation.
The 20-year trend may be +0.16 +/- 0.8 K following this position.
(This is just my hypothetical example, not an actual estimate of what
Crichton thinks.) This position would be called "nearly 50-50 expectation",
and against such persons James' claims make sense (if they are "rational" in
the sense that they make decision based on statistical expectation values).
===== End comment =====

Ko 1 M. (Kooiti Masuda)

James Annan said...


Thanks for the comment. It is true that people will not always take a single bet with small expected gain, if they are risk-averse. I would happily bet my ¥1 versus your ¥2 on a single coin toss, but might not bet ¥1,000,000 versus ¥1,000,001, even though the expected gain is the same! This can be formalised through a utility function, which is generally assumed concave (logarithmic is a typical shape - ie a coin toss to double vs halve ones wealth is a fair bet in terms of expected utility).

That's partly why I am looking for opponents whose judgement of the odds is so different to mine that a bet can appear highly profitable to both of us. Piers Corbyn has a history of betting, so certainly cannot pretend to be risk-averse, and Richard Lindzen and Pat Michaels/Chip Knappenburger publicly annnounced what appeared to be genuine betting offers. Shame they won't stand behind them.

Also note that in more general terms, a betting market can be used to reduce risk by hedging against adverse outcomes - this is effectively what people do by insuring against extreme events such as their house burning down. In that case, a rational risk averse person willingly takes on a bet with negative expected value.