On Sep 2, I was getting ready to report on my trip to Italy and my presentation to the World Federation of Scientists seminar in Erice, Sicily, when I was rudely interrupted by the publication of Mann et al 2008. It will take time to fully parse the situation, but the main framework is pretty clear. The addiction of Mann and the paleoclimate community to problematic Graybill bristlecone chronologies has not been cured. Indeed, Mann et al 2008 has made things worse, using even more fanciful data sets, such as serial (4 time) use of disturbed Kortajarrvi lake sediments.
I found the Erice conference very interesting. The topics were much more policy-oriented than I try to cover at the blog (climate was only one of many topics, others included energy supply, nuclear security, computer security). Over the next few months, I’ll relax these policies for some individual threads and pick up some of the themes at the conference, as these will undoubtedly be of interest to many readers – indeed, most of the themes will be of more interest to readers than the technical issues that I like to discuss.
But for today, you’ll have to content yourselves with my presentation. I had to submit a written paper and had a 20-minute talk. The presentation immediately prior to mine had used the HS (the IPCC 2001 version) as an unannotated “fact”, which was a good set-up for my presentation. The Erice conferences have a distinguished history of promoting openness in science even (and perhaps especially) in nuclear topics and I think that it was disappointing to many of them that climate scientists, of all people, should be anything less than 100% forthcoming with the provision of data and methods, and the idea of a climate scientist using personal Intellectual Property Rights as a pretext for refusing data and methods definitely did not sit well with scientists from other disciplines who are concerned, as citizens, about quantifying climate change.
Here is the written submission. Most readers here are familiar with the history of the dispute, but third parties aren’t and, points of detail such as different versions of Tornetrask, Polar Urals and Sheep Mountain obviously make no sense except in the context of an ongoing dialogue.
I then proceeded to discuss two problems which between the two of them, pretty much eviscerate all the IPCC AR4 reconstructions: (1) the divergence problem; and (2) differences between updated and IPCC versions of key sites (Tornetrask, Polar Urals and bristlecones). CA readers are familiar with these points, but I made new graphics in a consistent format illustrating the argument, which is pretty simple.
New versions of three important sites (Grudd’s Tornetrask, the unpublished Polar Urals update and Ababneh’s Sheep Mountain) have materially different MWP-modern differentials than the older versions used in the IPCC spaghetti graph (Briffa’s Tornetrask and Yamal; Graybill’s Sheep Mt/Mann’s PC1). Because so many purportedly “independent” studies are not actually “independent”, changes at only three sites cause a reversal of the MWP-modern relationship in 9 of 10 studies in the IPCC spaghetti graph and make the specific IPCC claim of AR4 unsupportable within their likelihood definitions. Here is the conclusion of my paper:
Although the statistical problems of the Mann et al (1998, 1999) reconstruction are by no means conceded within the reconstruction community, they have nonetheless been
identified for some time. Two blue ribbon U.S. panels have acknowledged these
criticisms, but IPCC 2007 did not.
Updated versions of Tornetrask, Urals and Sheep Mountain have opposite medievalmodern
differentials to the IPCC versions. Because virtually all of the IPCC reconstructions rely on these three sites and because the framework of MWP proxies in IPCC reconstructions is so limited, changes in only 3 site versions turn out to have a knock-on impact on 9 of 10 reconstructions, an issue which also affects the Mann et al 1999 reconstruction additional to all the other problems. IPCC failed to provide any accounting or reconciliation of the discrepant versions.
Adding to the problems of the IPCC 2007 reconstructions is the “Divergence Problem” – ring widths going down in the last half of the 20th century, while temperatures go up. In the absence of any such explanation and reconciliation, IPCC could not state within its probability definitions that: “[It is] likely that this 50-year period was the warmest Northern Hemisphere
period in the last 1.3 kyr.”
Verification of paleoclimate studies has been made far more onerous than necessary, by
the failure of authors to archive data and to properly document methodological procedures. Econometrics journals have dealt with similar problems by requiring authors to archive data (as used with accurate data citations to the precise version) and source code as a condition of reviewing. This procedure is recommended for paleoclimate journals as well. In addition, the U.S. National Science Foundation (NSF) has essentially abandoned its duties to ensure that paleoclimate authors comply with existing U.S. data archiving policies and many problems could be averted merely by NSF carrying out its duties.