Nearly all readers agreed with the proposal (of my most recent post) for a comprehensive mapping and crossdating of all dead and living trees within one or more altitudinal transects in the Polar Urals, with the objective of achieving a crossdated dataset of at least 1000 subfossil trees and 500 living trees, each with accurately recorded coordinates and altitude. As opposed to the puny dataset used in the CRU chronology, which has less than 10% of this population and which, as archived, lacks accurate location and altitude information.
Several readers speculated that the costs of such a dataset would not be all that large and ought to be within the reach of the enormous climate science budgets. Rob Wilson wrote in – from the perspective of a practising (and, in contrast to CRU, actively collecting) dendro – saying that neither should the costs of such a program be under-estimated nor the difficulty in getting funding, concluding that such difficulties were the major factor in the shortage of long high-latitude chronologies:
As a quick response to Steve’s idealised approach. Yup – all well and good and I agree with it all. The reality is that for such replication requires multiple fieldtrips, several years (decades for Scandinavian work for example) and funding (plus bods on the ground). The reality is not so easy and funding is far from easy to acquire if you are considering, fieldwork, analytical costs (RW, MXD, isotopes etc), salaries etc. That is why there are so few millennial long chronologies from the high latitudes. The material is waiting there to be collected.
In a comment to the post, I observed that there was a punch line to it, a clue which a few readers understood but many didn’t.
The punch line is this: according to articles in peer-reviewed academic literature, the proposed comprehensive survey has already been done. (Indeed, the description of the recommended program was taken almost literally from an article by Stepan Shiyatov, who deserves great credit for carrying out a scientifically rational program for over 50 years under what must have been difficult circumstances.
In today’s post, I’ll summarize the extent of the Shiyatov dataset. (As a caveat, today’s post relies on information in peer reviewed academic literature; I have not personally had access to a digital version of Shiytov’s data.)
The “Polar Urals” Site
Shiyatov’s Polar Urals site is located on the east slope of the Urals mountains slightly to the west of the Sob River, which flows through a rare pass through the Urals. On ex ante grounds, the location appears ideal for paleoclimate work, as the vegetation goes from alpine tundra to open forest and then to closed forest over relatively short distances (less than a km). The area has been essentially undisturbed by human settlement. Subfossil trees and stumps are plentiful in the alpine tundra.
Over the years, six altitudinal transects have been mapped: the first in 1968, the second in 1983 and the most recent four since 2000.
Locations, methodology and counts for the first two transects were provided in Shiyatov and Mazepa 2011 (from which the following synopsis is taken). The existence of the other four transects is mentioned in Mazepa et al 2011, but without details.
Transect 1 was established in 1968 (or perhaps 1960?) on the east slope of a low foothill (312.8 m) of the Urals range (see figure 1 below). It was 860 m long and its altitudinal range was from 265 m to 190 m. Its upper transect was at 66.7779N and 65.425E. Shiyatov mapped the location of each tree and sapling on a 1:100 scale (769 standing and fallen dead trees and more than 4500 live trees: Shiyatov and Mazepa 2011), measuring the morphometrics of each. Shiyatov took cross-sections from each dead tree, from which ring widths were measured, successfully crossdating cores from 667 trees, most failures having only 30-40 rings.
Transect 2 was established in 1983 on the southeast slope of the Rai-Iz Massif (a name to keep in mind), 5.5 km to the north-northwest of the first transect (see Figure 1 below). It was 430m x 20m, from 340 m to 280 m (the then timberline). Its upper limit was tat 66.89125N and 65.581E. At this transect, all trees had died off by the 19th century, the coldest period in the record, though saplings and young growth had been re-established in the 20th century. Shiyatov mapped 252 dead trees (and the saplings), again taking cross-sections from the dead trees, crossdating 221 dead trees: Shiyatov and Mazepa 2011; Mazepa et al 2011.
The combined count of subfossil cross-sections from these two transects is therefore 1021, of which 888 are crossdated. Mazepa et al 2011 reported that the inventory of cross-sections from dead trees had been increased to 2262 (more than double the 1021 collected from the first two transects), but did not provide information on the proportion that had been crossdated. However, given that 87% of the trees on Transects 1 and 2 had been crossdated, one presumes that well over 1500 trees have now been crossdated. (Not complaining, by the way, about the 888 crossdated trees from Transects 1 and 2.)
Neither Shiyatov and Mazepa 2011 nor Mazepa et al 2011 provide count information on crossdated living trees. Shiyatov 1995 reported that more than 400 cuts from dead trees (209 from Transect 2) and 350 cores and cuts from living trees had been collected. Shiyatov 1995 reported a chronology to 1992, indicating that there had been a coring program in 1992, subsequent to the Schweingruber program in 1991. (Further evidence of 1992 coring exists in Climategate documents.) There is also evidence of a coring program in 1996 (also within Climategate documents). Thus, it seems entirely possible that there are more than 500 crossdated living trees in Transects 1 and 2 (but even if there are only the 350 trees attested in Shiyatov 1995, this is still an order of magnitude larger than the CRU dataset.)
Briffa et al 2013 provided no site map for Polar Urals – an omission that would not be tolerated in a geological report. It is also an omission that strongly suggests to me that no one from CRU has ever been to Polar Urals (or Yamal) – a neglect that is not due to inadequate funding as CRU received over US$400,000 for the project of which the present article is the major output. (Annoyingly, the site maps in the Shiyatov articles lack grid information – an oversight that needlessly complicates interpretation and which reviewers should have caught.) Fortunately, Shiyatov and Mazepa 2011 provide information on the upper transect location accurate to the nearest second. This information is used to locate the two transects on Google Earth below. Shown for comparison are site location information from Briffa et al 2013 (see further discussion below.)
Figure 1. Site map of Shiyatov’s Polar Urals site. Exact (six-digit) locations of the upper end of each transect is given in Shiyatov and Mazepa 2011. The direction and bottom end of each transect is estimated based on the running text of Shiyatov and Mazepa 2011. The point-locations are derived from the table in B13 SuppMat 3. The Sob River is visible in the top right of the image shown below. The above image was created using RgoogleMaps, a very nice package that I used for the first time in making this image. I’ll show the code in a comment to demonstrate its facility.
Schweingruber and CRU
Unfortunately Shiyatov has not archived this exemplary dataset, which has accordingly not received the notice that it is due. The only Shiyatov measurement data archived at ITRDB is a selection of his 1968 measurement data from living trees (russ001.) Remarkably, Briffa et al excluded this data from their chronology (for reasons which I regard as unconvincing), resulting in the ironic situation that it appears that not a single measurement from Shiyatov’s institution was used in Briffa et al 2013.
If CRU didn’t use any Shiyatov measurements, what did they use?
In 1991, as part of his large-scale northern hemisphere sites (a survey that yielded the surprising Decline), Schweingruber surveyed a number of sites in NW Siberia, including Khadyta River in Yamal and the “Sob River” site (reported to be at 66 52N, 65 38E and 250 m). Schweingruber’s samples seem to have been taken from the area of Transect 2 (though this is only a guess – it’s too bad that Briffa et al 2013 did not bother giving scientifically accurate location information on the Schweingruber program). The 1991 sampling yielded 42 cores from 22 trees, all of which were measured for MXD and RW in Schweingruber’s lab in Switzerland.
As a followup (presumably in 1991 or 1992), Shiyatov sent 53 subfossil samples (50 trees) to Schweingruber for MXD and RW measurement. These samples seem to have been cores taken from Shiyatov’s subfossil disks (though this is just surmise on my part.) These were later combined with Schweingruber’s samples from living trees to make the “pou_la” dataset, available at NOAA ITRDB. Briffa et al 2013 provide some previously unavailable details: their PU05 (SupMat3) purports to provide identifications and spans (as measured by Shiyatov) for samples sent to Schweingruber. Unfortunately, the identification nomenclature at NOAA is inconsistent with the PU05 nomenclature and no concordance is available: this is something that is very desirable.
The pou_la combination was used in Briffa et al 1995 (Nature), an influential proxy article in the 1990s. As a claimed contrast to medieval warmth in the north Atlantic, Briffa et al 1995 asserted that the 11th and other medieval centuries were regionally cold in the Polar Urals and that 1032 was the coldest year of the millennium. This conclusion was diametrically opposed to the conclusions of Shiyatov 1995, which concluded that the medieval period had been warm in the Polar Urals. Shiyatov was listed as a coauthor of Briffa et al 1995 and was apparently unperturbed by the apparent inconsistency. The Polar Urals chronology of Briffa et al 1995 was important in “colding” the medieval period of the Jones et al 1998 reconstruction – a phenomenon that originally attracted my interest.
Many of the earliest Climategate emails (1996) are between Briffa and Russian dendros, including Shiyatov. Although Briffa et al 1995 (and subsequent work) was arguably a bowdlerization of Shiyatov’s research, Shiyatov and coauthors were grateful to Briffa for his interest in the work. With the collapse of the Soviet Union, they were desperate for money, a recurrent topic in many early Climategate emails. CRU found some money for them and , in return, Shiyatov and others provided CRU with copies of data not elsewhere available. In 1997, CRU received a copy of an expanded Polar Urals measurement dataset (briffa-treering-external/stepan/rai-iz.rwm), one which is considerably expanded in the medieval period from pou_la. This was included in the Climategate-1 dossier, but was not then connected to Polar Urals. More on this dataset on another occasion.
In 1999, at Schweingruber’s request, Shiyatov sent 32 additional samples (32 trees) supplementing periods of low replication in the pou_la data, especially the medieval period. A letter referring to the additional samples is in the CG1 dossier. Briffa et al 2013 (PU06 in SupMat 3) provide a covering email from SHiyatov to Schweingruber which, in addition to describing the location (stem/root) of the samples, also provided the span as measured by Shiyatov. In this case (unlike pou_la), a concordance is possible between the PU06 nomenclature and the polurula nomenclature. For reasons not explained in Briffa et al 2013, Schweingruber’s measurements cover significantly shorter periods than the span reported in the Shiyatov email: the average difference is 44 years, with a difference exceeding 100 years in some cases. (That the Shiyatov spans derive from actual measurements can be proven, though this is outside the scope of the present post.)
In 2002, Esper incorporated the polurula data into the Polar Urals data used in Esper et al 2002 – the only multiproxy study of the period that used Polar Urals rather than Briffa’s 2000 Yamal hockey stick. In 2005-6, D’Arrigo et al also incorporated the polurula data into their spline chronology; for their final reconstruction, they used the Briffa 2000 Yamal chronology, which they incorrectly labeled as coming from Polar Urals (and refused to correct.) I noticed the additional core count in a draft of D’Arrigo et al 2006 and in late 2005 began to report the inconsistency between the implicit RCS chronology inclusive of polurula and the Yamal super-stick. The discrepancy between the Polar Urals chronology inclusive of polurula and the Yamal superstick has been a recurrent issue at CA.
Briffa et al 2013
The subfossil data in Briffa et al 2013 is drawn entirely from the Schweingruber measurement data. Although Shiyatov (one of the listed coauthors of Briffa et al 2013) has crossdated at least 888 subfossil cores from Transects 1 and 2, Briffa et al 2013 only used Schweingruber’s measurements, a less than 10% subpopulation. From this already small dataset, CRU argued that root collar samples were inhomogeneous and excluded 21 of 83 trees. In their recommended version, the count in the early 11th century is only two trees – far below recommended levels. Indeed, the supposed low replication at Polar Urals is used by CRU as an argument in favor of Yamal (which has its own issues.)
The living tree inventory of Briffa et al 2013 also begins with the Schweingruber data. ^ crossdated trees from Shiyatov’s 1968 program are at NOAA ITRDB (russ001.rwl), but these were excluded by CRU, who argued that, unlike the Schweingruber data, russ001 lacked MXD data. IN my opinion, this is all too typical CRU ad hockery, since lack of accompanying MXD data was not an issue for their Yamal data (or to my knowledge in any predecessor CRU publication.)
To the Schweingruber data, CRU added two small measurement datasets (purlasi and purlasi_sc), which appear to have been measured by Alexander Kirdyanov at Krasnoyarsk from samples provided by Shiyatov’s institution (presumably along the lines of the earlier arrangement with Schweingruber.) The reported altitudes of both purlasi and purlasi_sc are lower than the altitudes of Transects 1 and 2. There is a substantial apparent inhomogeneity in the purlasi_sc dataset, which has nearly double the average ring width of any of the other datasets and which is reported to be about 5-6 km distant from Transect 1. The inhomogeneity is of the same order of magnitude as the root collar inhomogeneity, but CRU do not describe a protocol which objectively precludes the one, while accepting the other. Again a topic for another post.
Briffa et al 2013 raises many questions, some of which I’ll cover in other posts. In concluding today’s post, I wish to focus on CRU’s failure to use the seemingly comprehensive Shiyatov dataset. Some questions:
- did CRU ask Shiyatov for the complete dataset of crossdated subfossil and living cores?
- if so, did Shiyatov refuse and why?
- if not, why didn’t they ask?
- did CRU not know about the existence of the Shiyatov crossdated dataset? if they did know, why wouldn’t they ask to use it: particularly since Shiyatov and associates were listed as coauthors?
- did any reviewers take issue with CRU’s failure to use the Shiyatov dataset? If so, how did CRU respond to the reviewers?
I’ve asked Osborn about this at Real Climate. My comment (see here) was held up in moderation for over a day, but has now appeared. Osborn has answered some other comments and will perhaps explain this as well.
Over and above the question of why CRU didn’t use the Shiyatov data is the question of why CRU didn’t even report the existence of the Shiyatov dataset in their history of dendro work at Polar Urals. It’s hard to imagine information more relevant than the apparent existence of 888 crossdated subfossil trees at Transects 1 and 2 plus hundreds of crossdated living trees. But these numbers are not reported in Briffa et al 2013. One wonders why.
Update: Tim Osborn stated at Real Climate:
We were aware that many additional wood samples were collected, measured and cross-dated in the Polar Urals by our co-authors, as part of their excellent ongoing ecological monitoring at the tree-line. In fact there are even more data, from more recently sampled material. As with the previous data, these are a complex mix of stem, root, prostrate forms, etc. and indeed many samples will not be suitable for dendroclimatological analysis using the basic RCS approach.
A preliminary analysis of some of the “stem” samples produces a similar picture of tree-growth change when using RCS processing as that shown by the Polar Urals chronology in our paper. We made this preliminary check to satisfy ourselves that we could proceed with our publication with the knowledge that we were not publishing a chronology that was likely to be contradicted when the more recent samples are analysed and published.
It was evident that much additional work will be necessary to examine and assess their suitability (and potential biases) when processing these data, and we had already demonstrated in our paper the difficulties in using the existing root-collar samples for example. I repeat that some, or many, of these will not be suitable for straightforward RCS processing because they are from prostrate or root-collar samples.
The dendrochronological data from this recent sampling have not yet been published and it is the prerogative of the Ekaterinburg laboratory to publish the first dendroclimatological analysis of the data that they have spent many years and extensive effort in collecting and processing. We hope to continue our long-standing collaboration with our Russian colleagues in this work.
Your question and other commentary at your blog may give readers the false impression that we have published using an inadequate dataset. This is ironic given your advocacy for publishing (a biased version of) this chronology when you believed that it would support an elevated Medieval Warm period, advocacy that extended to questioning our integrity for not doing so. It is unfortunate that you fail to acknowledge the careful analysis reported in Briffa et al. (2013) to demonstrate the biases that would arise from a naïve use of the Polar Urals update data. It is also unfortunate that you fail to acknowledge that Briffa et al. (2013) was based on a significantly increased set of tree-ring data for the adjacent Polar Urals and Yamal regions, with overall replication that is much improved over previous work.
As always, one has to watch the pea. The original transects were done in 1968 and 1983, yielding 888 crossdated subfossil trees and hundreds of living trees. And yes, Shiyatov and associates have done new work since 2000, but that is not an excuse for CRU failing to utilize subfossil data that was collected 30-50 years ago. Puh-leeze. Nor does this excuse CRU’s failure to draw attention to size of the data that they didn’t use.
Nor do I accept Osborn’s suggestion that I have endorsed the use of radially deformed trees. A concern with such trees (strip bark bristlecones) has been a longstanding concern at CA.
Shiyatov et al 2011, url Climate-driven dynamics of the forest-tundra vegetation in the Polar Ural Mountains
Mazepa et al 2011, url Climate-Driven Change of the Stand Age Structure in the Polar Ural Mountains
Shiyatov 1995 url Reconstruction of climate and the upper treeline dynamics since AD745 by tree ring data in the Polar Ural Mountains..
Briffa et al 1995, ^.