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Category: climate science
Posted on: July 14, 2006 12:30 PM, by William M. Connolley
There is apparently a strange thing called the Wegman report. Sadly that link only contains Smokey Joe Bartons comments on selected extracts (does anyone know where the full thing is? Is it published? Also quite what the committee/panel is, is rather vague. [Update! Aha... I should have known: since it was Per who commented on it, and since it reads like it was written by M&M, the dark side pointed me towrds the full thing]). Still, what did they say? (BTW, in case you hadn't realised, this is yet more HS stuff :-)
the paleoclimate reconstruction... does not provide insight and understanding of the physical mechanisms of climate
change... What is needed is deeper understanding of the physical mechanisms of climate change Yup, nothing like stating the bleedin' obvious. Anything better in there?
evaluation by statisticians should be standard practice. This evaluation phase should be a mandatory part of all grant applications and funded accordingly. Aha! He wants more money and more work for statisticians. Not a particularly odd thing for him to say, but I don't see hard-pressed cliamte researchers wanting to give up their grant money. Unless there is extra available, perhaps from cancelling the "war on terror".
authors of policy-related documents like the IPCC report, Climate Change 2001: The Scientific Basis, should not be the same people as those that constructed the academic papers." Sounds good, but probably naive expressed like that. Who else, apart from people who write climate papers, can assess and synthesise the science?
As statisticians, we were struck by the isolation of communities such as the paleoclimate community that rely heavily on statistical methods, yet do not seem to be interacting with the mainstream statistical community. The public policy implications of this debate are financially staggering and yet apparently no independent statistical expertise was sought or used." Dubious. It gets said again and again that the HS isn't a major part of attribution, but no-one listens. Probably a good argument for not letting people who know nowt about climate too close to it. I'm not sure about the isolated bit... maybe it just means Wegman doesn't know Mann. But then Mann doesn't know Wegman... does that make W isolated?
As mentioned earlier in our background section, tree ring proxies are typically calibrated to remove low frequency variations. The cycle of Medieval Warm Period and Little Ice Age that was widely recognized in 1990 has disappeared from the MBH98/99 analyses, thus making possible the hottest decade/hottest year claim. However, the methodology of MBH98/99 suppresses this low frequency information. This is weird, and appears to mix up different things. I haven't seen anyone previously claim that the MBH method suppresses low-f info thats in the proxies. If tree rings don't have the info, it can't create it. The assertion about what was widely recognised in 1990 is dubious, and appears to be a re-run of the IPCC '90 fig 7.1 stuff again (see http://en.wikipedia.org/wiki/MWP_and_LIA_in_IPCC_reports).
Um... so, that was fun, but the full report would be more interesting.
OK, picking a bit from that:
[M&M 2003] ... claimed that using the MBH98 methodology and the Northern Hemisphere average temperature index for the period 1400-1980 shows that temperatures in the 15th century exceeded those of the late 20th century. In particular, they claim that MBH98's incorrect usage of PCA alone resulted in the well-known "hockey stick" shape. This is a bit weird. If using MBH98 produces a warm 15th C, how can they also claim it always produces a HS?
The Wegman and North Reports for Newbies
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November 6th, 2007
In recent discussion of the Weblog 2007 Awards, several commenters at other blogs have argued that our criticisms of the Mannian parlor tricks have been "thoroughly refuted and discarded by climatologists, published in a credible journal"; that "other professionals in the field who also have "looked in great detail at the problem at hand" and have come to the conclusion that rather than McIntyre's findings being "valid and relevant", they instead have found them to be "without statistical and climatological merit"; that CA "fluffed on the whole hockey stick thing". See for example here
Omitted in these references are the fact that the people described as "climatologists published in a credible journal" or "professionals in the field" are none other than Wahl and Ammann, serial coauthors with Michael Mann, students of Mann, who are not independent of the controversy. Indeed, they largely use (without citation or attribution or even acknowledgment to Michael Mann) arguments originally published at realclimate (and already responded to in MM 2005b(EE). Aside from their lack of independence, neither Ammann nor Wahl qualify as statistical authorities. Ammann did his undergraduate work in geology; Wahl in divinity. While this does not exclude them from having potential insight in the matter, it is evidence that one should not necessarily expect a sure grasp of mathematical and statistical issues and that their conclusions cannot be relied upon uncritically, even if Stephen Schneider accepted their article.
Readers interested in a third party view of the matter are far better off consulting the North Report, the Wegman report, (particularly) Wegman's Reply to Questions and Richard Smith's account of the 2006 American Statistical Association session. All of these individuals are vastly more eminent than Ammann and Wahl. Wegman, in particular, has been Chair of the National Academy of Sciences Committee on Theoretical and Applied Statistics and is a legitimate statistical expert. His comments on the Wahl and Ammann preprint are very acute and have not received appropriate consideration.
I've collated some of these remarks for the benefit of new readers who haven't been following this particular story. Please read the comments below using the analogy from the previous post: see if any of our criticisms of Mannian parlor tricks have been refuted – as opposed to whether someone arguing that you can re-tool the trick to still saw the woman in half a different way. (And for this latter, pay particular attention to Wegman's comments on Wahl and Ammann later in the post.)
The Wegman Report
The original Wegman Report is online here. Here are some excerpts from this report: