By now, anyone who follows the climate blog wars knows that a new battle is underway over the standard temperature reconstruction popularly known as the “hockey stick”. Although it has been declared thoroughly shattered many times, apparently it must be attacked again and again.
Over the last few days, self-appointed climate “auditor” Steve McIntyre has made several insinuations concerning the work of UK dendro-climatologist Keith Briffa, focusing on the recently released Yamal series of tree-ring measurements. Along the way, he has once again rehashed an oft-repeated accusation that “cherry-picking” of proxy sites is endemic in the paleo-climatological community that he disdainfully calls the “Hockey Team”. But this time, McIntyre has outdone himself, comparing the repeated use of the Yamal tree-ring chronology in paleoclimatology studies to a “crack cocaine” addiction.
Of course, as this controversy is breaking out in my geographical back yard, I had to take a closer look (admittedly Canada is a larger back yard than most).
In brief, McIntyre’s claims focus on Briffa’s Yamal tree-ring series, a Siberian chronology that combines older fossilized tree samples with a small number of living trees. Briffa’s series was based on a chronology from two Russians, Hantemirov and Shiyatov. Apparently, McIntyre had been seeking access to the chronology for some years, but only recently managed to get hold of it.
According to McIntyre, “problems” with the Yamal series are fatal, not only to Briffa’s own work, but to most of the standard reconstructions of the temperature of the past millenium, which consistently show anomalous warming in the late 20th century.
McIntyre’s diatribes have led to widespread accusations of “cherry-picking” and general scientific misconduct against Briffa and other paleo-climatologists (for example, see the ever befuddled but angry Tom Fuller in Examiner.com). And McIntyre’s claims have even been construed, both in the “denialosphere” and at least two “mainstream” newspapers, as a crushing blow to the IPCC and the scientific consensus on climate change. The UK Telegraph’s James Delingpole opined that the controversy showed climate science was a “MASSIVE lie”, while Ross McKitrick’s libel-flirting diatribe in the National Post claimed that “what lies at the core is either flawed, misleading or simply non-existent” (more on McKitrick below).
An unverified accusation of malfeasance is made based on nothing, and it is instantly ‘telegraphed’ across the denial-o-sphere while being embellished along the way to apply to anything ‘hockey-stick’ shaped and any and all scientists, even those not even tangentially related. The usual suspects become hysterical with glee that finally the ‘hoax’ has been revealed and congratulations are handed out all round. After a while it is clear that no scientific edifice has collapsed and the search goes on for the ‘real’ problem which is no doubt just waiting to be found. Every so often the story pops up again because some columnist or blogger doesn’t want to, or care to, do their homework. Net effect on lay people? Confusion. Net effect on science? Zip.
Yet McIntyre’s supporters suggest that McIntyre himself can not be held responsible for such excesses. Roger Pielke Jr., ever ready to defend McIntyre against real climate scientists exonerated McIntyre, pointing to a belated clarification from McIntyre:
I don’t wish to unintentionally feed views that I don’t hold. It is not my belief that Briffa crudely cherry picked. My guess is that the Russians selected a limited number of 200-400 year trees – that’s what they say – a number that might well have been appropriate for their purpose and that Briffa inherited their selection … [Emphasis added by Pielke]
Without an explanation of how the selection of this sample of the available data had been performed, the suspicion of `cherrypicking’ would linger over the study, although it is true to say that Hantemirov also had very few cores in the equivalent period, so it is possible that this selection had been due to the Russian and not Briffa.
Now where did he get the idea that cherry-picking might be a possible issue? Well, when McIntyre presented his initial analysis of the Yamal chronologies on September 26 he noted:
I presume that these 17 ring-width series from living larches are a sample from a larger program on living larches. This graphic shows the use of over 30 cores from about 600 to 1500 and the use of about 17 cores in the 19th and 20th century (presumably the 17 cores from living trees.) …
Rob Wilson could do that in an hour. What about the rest of the Yamal data? Where is it?
To what extent is the Yamal HS a product of the selection process and to what extent is it climatic? Without the complete data set, it is impossible to set aside the troubling thoughts that one is faced with in these circumstances. [Emphasis added]
The obvious inference was, as Ross McKitrick put it in a subsequent comment, that the 20th century “sub-sample” had not been, ahem, “randomly selected”.
In subsequent comments, McIntyre continued to insist that someone, whether Briffa or the Russian team, had possibly “cherry-picked”, or at least not “randomly selected”, the Yamal living tree sub-sample:
As to whether the selection was previously made by Hantemirov and Shiyatov or not – I discussed this in the previous post and noted that there was evidence that the selection might have been made by them.
Of course, soon after Briffa confirmed that the underlying data set he used was exactly the same as the Russian team (but processed differently), and that, in general, he “did not select tree-core samples based on comparison with climate data”.
In the face of that forthright assertion, and in the absence of any evidence whatsoever of a more complete living tree sample to be “cherry-picked”, McIntyre “moved on”.
But McIntyre’s insinuations of “cherry-picking” (presumably of a less “crude” variety) also focused on Briffa’s “failure” to augment the “thin” Yamal living tree sample with a nearby data set from Schweingruber that contained 34 tree-ring samples from living trees. This was contrasted with Briffa’s augmentation of Avam-Taymir chronology (also from Siberia).
While Yamal stayed unchanged in Briffa et al 2008, the Taimyr series was modified noticeably, becoming the “Avam-Taimyr” series. … One doesn’t expect Team adjustments to leave even small scraps on the table and this proved to be the case here as well – the added data substantially increased 20th century values and substantially lowered 1150-1250AD values, thereby altering the medieval-modern differential in favor of the 20th century.
The intended insinuation was obvious. The barely-veiled accusation is that Briffa selected sample sets and even altered his methodology to produce the desired result, in both the Yamal and Avam-Taymir chronologies.
In fact, the Yamal Divergence thread contains no fewer than 30 references to cherry-picking, including this from McIntyre himself:
I’d be inclined to remove the data affected by CRU cherrypicking but will leave it in for now.
In another comment on that thread, McIntyre distinguished two sorts of supposed “cherry-picking”: trees within a site vs. sites within a multi-proxy study.
Jacoby, D’Arrigo, whatever other faults they may have, use the entire crossdated population from a site. (They cherry pick sites, but don’t cherry pick trees within a site.)
More graphically, McIntyre explained the situation thus:
However, as CA readers know, the resulting Yamal chronology with its enormous HS blade was like crack cocaine for paleoclimatologists and got used in virtually every subsequent study, including, most recently, Kaufman et al 2009.
At least he’s consistent with the anaology – that’s how he also characterized the Yamal series in the first post on the newly-released data set:
I’m assuming that CA readers are aware that, once the Yamal series got on the street in 2000, it got used like crack cocaine by paleoclimatologists.
Apparently, the world’s leading paleo-climatologists are all addicts and Briffa is cooking up the stuff they need, like some backroom chemist. Nice.
Such remarks could offend some sensibilities, even at controversial, “edgy” right-wing publications like Canada’s National Post. Enter Ross McKitrick, McIntyre’s some time co-author, who has written an analysis in the Post deemed more suitable for a wider audience. The article is entitled “Defects in key climate data are uncovered”, while the secondary headline screams:
Only by playing with data can scientists come up with the infamous ‘hockey stick’ graph of global warming
McKitrick’s version of the Briffa Yamal saga covers much of the same ground as above, and comes to much the same conclusion (if expressed slightly more circumspectly):
Thus the key ingredient in most of the studies that have been invoked to support the Hockey Stick, namely the Briffa Yamal series, depends on the influence of a woefully thin subsample of trees and the exclusion of readily-available data for the same area. Whatever is going on here, it is not science. [Emphasis added]
But make no mistake, every point that McKitrick makes has been made before in cruder (albeit more elliptical) fashion by McIntyre. In fact, McKitrick has helpfully given us a reference guide to the ClimateAudit posts he relied on in constructing his version in this comment summarizing the Briffa affair.
I can’t leave McKitrick’s piece without pointing out his over-the-top conclusion.
The surface temperature data is a contaminated mess with a significant warm bias, and as I have detailed elsewhere the IPCC fabricated evidence in its 2007 report to cover up the problem. Climate models are in gross disagreement with observations, and the discrepancy is growing with each passing year. The often-hyped claim that the modern climate has departed from natural variability depended on flawed statistical methods and low-quality data. The IPCC review process, of which I was a member last time, is nothing at all like what the public has been told: Conflicts of interest are endemic, critical evidence is systematically ignored and there are no effective checks and balances against bias or distortion.
Needless to say, there is not one statement here that stands up to any scrutiny whatsoever (although there are one or two that might keep litigation lawyers busy for a while).
Somehow, we are to believe that the mountainous scientific corpus that overwhelmingly demonstrates the existence of global warming and its anthropogenic genesis is a vast conspiracy, one involving thousands of scientists and other professionals. And we must further believe this conspiracy has been exposed by the scattergun technical analysis of a mining consultant turned blogger.
And for all this, we must accept the word of economist McKitrick, whose main claim to fame in climate “science”, apart from his association with McIntyre, is as co-ordinator of an execrable error-ridden review of climate science (the Independent Summary for Policy Makers), produced for a think tank (the Fraser Institute) known to receive significant funding from some of Canada’s largest oil and gas companies.
I don’t think so.
Steve McIntyre apparently wants to be taken seriously as a professional scientific investigator. Well then, he should try doing real science, instead of indulging in his usual stream-of-consciousness conflation of semi-technical analysis and accusatory snark. It is only in exposing his half-baked ideas to the scientific peer-review process that the merit, if any, of his ideas and analysis can be assessed.
Nevertheless, given the wide dissemination of McIntyre’s “analysis”, Keith Briffa has responded with a quick reaction, as noted above, with the promise of more to come.
The basis for McIntyre’s selection of which of our (i.e. Hantemirov and Shiyatov’s) data to exclude and which to use in replacement is not clear but his version of the chronology shows lower relative growth in recent decades than is displayed in my original chronology. He offers no justification for excluding the original data; and in one version of the chronology where he retains them, he appears to give them inappropriate low weights. I note that McIntyre qualifies the presentation of his version(s) of the chronology by reference to a number of valid points that require further investigation. Subsequent postings appear to pay no heed to these caveats. Whether the McIntyre version is any more robust a representation of regional tree growth in Yamal than my original, remains to be established.
My colleagues and I are working to develop methods that are capable of expressing robust evidence of climate changes using tree-ring data. We do not select tree-core samples based on comparison with climate data. Chronologies are constructed independently and are subsequently compared with climate data to measure the association and quantify the reliability of using the tree-ring data as a proxy for temperature variations.
We have not yet had a chance to explore the details of McIntyre’s analysis or its implication for temperature reconstruction at Yamal but we have done considerably more analyses exploring chronology production and temperature calibration that have relevance to this issue but they are not yet published. I do not believe that McIntyre’s preliminary post provides sufficient evidence to doubt the reality of unusually high summer temperatures in the last decades of the 20th century.
We will expand on this initial comment on the McIntyre posting when we have had a chance to review the details of his work. [Emphasis added]
It may be amazing to some that Briffa has responded so mildly to McIntyre’s wild insinuations and has deigned to engage him on substantive issues. Nevertheless, I’d say McIntyre was pushing his luck when he offered to host a page for Briffa and repeated his Yamal “crack cocaine” remark in the same post!
As for the National Post, it has demonstrated once again that an unreasoning ideological diatribe against climate science, unadorned by any factual analysis, is the surest route into its pages. Alas, further exploration of the Post’s perfidious campaign against climate science (now into its eleventh year), will have to wait for another time.