Wednesday, August 09, 2006

Steve McIntyre wants to bet over global warming proxies

Over at ClimateAudit, the issue of betting over global warming came under discussion in a comment thread. McIntyre eventually stepped in, not to bet about global warming itself but over using tree ring data as proxies for assessing historical temperatures when instrumental records weren’t available:

So I’ll make a counter-proposal and I’d be prepared to bet in size and one where the results can be determined.

Do any of the warmers want to bet that European tree rings in the very warm year of 2003 did not show very wide rings such as predicted by the MBH assumption of a linear relationship between temperature and ring width?

Or that Sheep Mountain bristle ring widths in the period 1990-2005 were as wide or wider than projected by a linear model - we can define the model, but essentially it’s the linear assumption of MBH.

I’ll bet either.

McIntyre is one of the people challenging the MBH study in 1998 that recreated global temperatures over the last 1000 years. Personally, I don't really care about that debate - a single 1998 study doesn't determine whether anthropogenic global warming is happening. I also don't know what Steve M.'s position is on AGW, although his comments on the thread suggest he's one of the skeptics claiming there's a natural warming. If he thinks temps should decline anytime soon, he should be interested in betting me over temps.

But he wants to bet over proxies. I don't know enough to judge the fairness or importance of his bet. If it's a continued rehashing of that 1998 study, his bet offer is unimportant to the climate debate. If it concerns the validity of later reconstructions, then it may have some importance for one (just one) of the lines of evidence supporting AGW, and people who are involved in that field might want to consider it.

Finally, Steve M claims I "quickly withdrew when it came to betting against me on proxies." No, I withdrew because I'd been accused of hijacking a comment thread to a post that was unrelated to betting. I'm very happy to negotiate terms over a bet with Steve M. or someone else regarding a bet over global warming. As for tree ring proxy measurements, I'm just highlighting it here in case anyone else is interested.

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