I’ve talked recently about the phenomenon of cherry picking tree ring chronologies with upticks in the small-subset (10-20) compilations used in typical Hockey Team multiproxy studies (e.g. Jones et al 1998; Crowley and Lowery 2000, etc., most recently Osborn and Briffa, 2006; and to a slight lesser extent D’Arrigo et al, 2006 (where there was a discipline resulting from the need to report their own extensive fieldwork.) I’ve referred in passing to evidence that there has been a large-scale decline in density and ring width over hundreds of sites and it might be useful to do a quick survey of this evidence – which comes ironically mainly from Briffa himself. Given that there has been an overall decline in both measures for a population of over 300 sites supposedly chosen for temperature sensitivity, what are the chances of picking (by chance) the Yamal, Mongolia, bristlecone and foxtail series – all with strong growth. None.
Also see posts 529, 570 and 586.
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The Polar Urals temperature reconstruction (Briffa et al, 1995) has been a mainstay of multiproxy studies. More data was collected at this site in 1998 (russ176), but in the two new studies (Osborn and Briffa, 2006; D’Arrigo et al., 2006), they relate their site selection to the Polar Urals, but substitute the Yamal RCS series (oddly, D’Arrigo et al. use the Polar Urals data for the spline standardization (STD)). What accounts for the Yamal substitution?
Also see here here here here.
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Just when you think that you’ve heard of all the possible problems with tree rings, the newest issue comes from “positive” and “negative” responders to temperature within the same site. These issues are discussed in a number of articles by various post-docs associated with Jacoby and D’Arrigo with the latter as co-authors. So in fairness to them, they are not just ignoring the problem of the failure of tree rings to respond to post-1980 temperature – although the issue is dealt with more candidly in specialist articles than in the general literature. Also in fairness to Jacoby who I’ve criticized for failing to archive information (and will continue to criticize), unlike Mann, he’s collected a lot of information. When I twitted him for supplying data to Mann for use in Mann and Jones [2003] and then refusing to supply to me, he said that he didn’t supply it to Mann and that he had no idea how Mann got the data and seemed to have antipathy towards all data re-processors. However as I’ve said before, exploration geologists also go into remote spots of the world and it would never occur to them that this labor made them owners of the data. But it’s the compoanies that manage the geologists. I’ve got a bigger beef with NSF being co-opted by dilatory archivers than even the dilatory archivers. But on to positive and negative responders. Continue reading →
There’s been a relatively lively discussion at realclimate here on O&B . I’ve got a couple of thoughts for now on (1) the independence of authors and (2) differences between datasets – two issues which I’ve frequently discussed. Continue reading →
D’Arrigo, Wilson and Jacoby [2006] represents state-of-the-art in dendrochronology and is hot off the press. It is unique among such studies in using a considerable amount of up-to-date data and is relatively candid about its results. I’ll try to discuss it in more detail. Here I want to pick up on one issue that featured strongly in my review of Osborn and Briffa – my inability to replicate the claimed correlation of bristlecones to gridcell temperature. Remarkably DWJ06 make the same point: thus we have the remarkable situation of two dendrochronological studies published in the same week, making completely opposite claims about the correlation of bristlecones and foxtails to gridcell temperature. Continue reading →
David Stockwell was intrigued by the seeming “robustness” of O&B results. There’s a reason for it: pretty much every one of the stereotyped Hockey Team proxies that are common to multiple studies are included in the O&B collation: bristlecones, Briffa’s re-processed series, Thompson’s Dunde and Guliya, Jacoby’s Mongolia. Pretty much every rascal has been gathered into one corral. The non-tree ring series – Chesapeake Bay, Greenland dO18 – do not show elevated 20th century results, but simply function as noise, allowing the stereotypes to dominate.
I’ve tried to do a collation of the proxy series used in O&B. There are two main problems – (1) some of the series attributed to Esper cannot be replicated using the citations: Quebec (cana169); Tirol (germ21); Mangazeja(russ067, russ068); Boreal/Upperwright. Some of the Briffa versions were previously archived at his website, but the measurements are unarchived (Tornetrask update; Yamal; Taimyr; Boreal/Upper Wright). Continue reading →
Osborn and Briffa [2006] , published today in Science, cannot be considered as an “independent” validation of Hockey Stick climate theories, because it simply re-cycles 14 proxies, some of them very questionable, which have been repeatedly used in other “Hockey Team” studies, including, remarkably, 2 separate uses of the controversial bristlecone/foxtail tree ring data.
Also even more remarkably, they have perpetuated the use of Mann’s erroneous principal components method in one of their key proxies.
Peer reviewers and editors at Science have failed to ensure compliance by Osborn and Briffa with journal data archiving policies, a frequent defect in paleoclimate reviewers for Science, as data for the study is not archived, nor is much of the source data.
Of the source data which is archived, some is password protected, presumably for international security. Within the available record, many peculiar inconsistencies can be observed affecting both this study and Esper et al [2002], a study previously published in Science also with a non-existent data archive.
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You’d think that there would be little left to figure out about Mann’s PC methods. I’ve been re-examining the PC1 in Mann and Jones [2003] and Jones and Mann [2004] for reasons that I’ll explain further in my next post. The data is at WDCP here but I wasn’t able to replicate this result and had basically given up temporarily. Since I don’t like loose ends, it’s irritated me. Out of the blue, I figured out what he did. The solution was splicing of Mannian proportions. Continue reading →
The National Research Council of the National Academies has empanelled a blue-chip committee to study "Surface Temperature Reconstructions for the Past 1,000-2,000 Years". The chairman will be Gerald North. The request came from the House Science Committee – I presume that they are trying to assert possession over this piece of turf. 8-10 speakers are being requested to address the panel on March 2-3 with a reception on Thursday night. Mc-Mc have accepted an invitation to appear.
The reception should be interesting. I’ve played interclub squash leagues in Toronto for nearly 40 years and one of the things that I like about them is that you have drinks and dinner with your opponents. I’ve always thought that English traditions for sports in that respect were very civilized. When I played rugby in England (I played for Corpus Christi College at Oxford), you’d have beer afterwards with your opponents and exchange beers with the guy that tackled you the hardest. I think that I overlapped with Bill Clinton by one year, but don’t recall meeting him. I guess Mann and I will have to swig down a few and maybe join in some rugby songs. Anyway here’s the invitation: Continue reading →
What I’m going to show here is that the MBH98 method can be reduced to a few lines of code and, in doing so, show some other interesting results as well. Today I’m just going to get to the reconstructed temperature PCs, but I’ll show that these are linear in the proxies and later show that the NH temperature index is, up to a very slight linearization in the RPC re-scaling step, also linear in the proxies. We reported this as long ago as MM03, but I’ve never shown this in detail. The result is important because it contradicts claims by MBH, von Storch et al [2004] and Zorita et al [2003] that the effect of individual proxies cannot be isolated. I’ve been massaging this material for a long time and plan to submit it for publication. Recently, Mann has argued that RegEM is a magic bullet and I’ve been re-visiting my methodological notes.
In the important case where only one temperature eigenvector is reconstructed (the AD1400 step in MBH98 and the 1000-1399 step in MBH99), I’ll show that the weights assigned to each proxy are proportional to the correlation of each proxy to the temperature PC1 – demonstrating the essential similarity of MBH98 methodology to “correlation weighted” proxies used in other studies [e.g. Mann and Jones, 2003].
The procedure described here (or close variations up to re-scaling) has been used since MM03. I have reconciled all results step by step to Ammann and Wahl source code (discussed last May) and have analysed MBH98 source code. I’ll discuss some nuances pertaining to weighted regression in the next instalment. (I apologize for transpose where you’ll have to read T as a transpose, as I can’t figure out how to do a superscript on “WordPress”). Continue reading →
Climate Audit 
National Academies Panel on Temperature Reconstruction
The National Research Council of the National Academies has empanelled a blue-chip committee to study "Surface Temperature Reconstructions for the Past 1,000-2,000 Years". The chairman will be Gerald North. The request came from the House Science Committee – I presume that they are trying to assert possession over this piece of turf. 8-10 speakers are being requested to address the panel on March 2-3 with a reception on Thursday night. Mc-Mc have accepted an invitation to appear.
The reception should be interesting. I’ve played interclub squash leagues in Toronto for nearly 40 years and one of the things that I like about them is that you have drinks and dinner with your opponents. I’ve always thought that English traditions for sports in that respect were very civilized. When I played rugby in England (I played for Corpus Christi College at Oxford), you’d have beer afterwards with your opponents and exchange beers with the guy that tackled you the hardest. I think that I overlapped with Bill Clinton by one year, but don’t recall meeting him. I guess Mann and I will have to swig down a few and maybe join in some rugby songs. Anyway here’s the invitation: Continue reading →