Contrary to a myth believed in by the climate science “community”, most recent multiproxy reconstructions are not “independent” – they merely recycle the same stereotypes with slightly different weighting methods. In an email (1140039406.txt) in which Briffa urges Overpeck not not to “over egg the pudding”, he stated: “Peck, you have to consider that since the TAR , there has been a lot of argument re “hockey stick” and the real independence of the inputs to most subsequent analyses is minimal.”
CRU contributed three of the canonical proxies – Tornetrask, Taimyr and most importantly, Yamal. Yamal was very much in the news when Climategate broke. In my submissions, I identified Yamal as an important issue. Needless to say, it’s been ignored.
I’m going to re-visit the inconsistency issue today – I’ve collected information from a number of sites in the general Yamal area on the Hantemirov and Shiyatov location map below (Polar Urals and Nadim are from slightly outside the four corners of the location map.
Figure 1. Inset chronologies on H-S location map. For the purposes of this map, I’ve done the chronologies by making a age-curve from the entire population of subfossil cores in the Climategate documents and developing a chronology for each site from the residuals for this standard fit (taking one size fits all to a regional scale). Red – slarch; green – spruce. The original Yamal chronology (modern portion) is also shown.
The statistical problem is, of course, the inconsistency between the decline observed in the majority of northern tree ring proxies and the extreme HS-ness of Briffa’s Yamal chronology, especially after it’s been Mann-smoothed or Kaufman-smoothed. In typical small subset multiproxy studies, it ends up making a disproportionate contribution to the overall HS-ness of the reconstruction – an effect that we observed last fall with Kaufman et al 2009, for example.
The controversy last fall arose over the very small population of cores in the Briffa 2000/Briffa 2008 Yamal reconstruction together with an inconsistent pattern in a nearby Schweingruber site (Khadyta River) which showed the characteristic decline.
Examined closely, Briffa didn’t actually disagree with any of the observations in my posts. Instead, he attempted to cooper up the Yamal reconstruction by adding cores from the Porzayakha and Yadoyayakha Rivers, which yielded a somewhat attenuated HS (but a HS nonetheless.)
Briffa stated: “We have also taken the opportunity to acquire and incorporate additional data from the 3 original sites, in this analysis.” (The Climategate documents show that they had extensive Yamal data since the 1990s, including the “new” data for Porzayakha and Jahak.)
The Climategate documents contain new and relevant information on the Yamal samples. The file briffa-treering-external/ecat/yamal/sfw-list provides the location of many samples, showing that many subfossil samples came from the Khadyta River ( a point confirmed by the location map in Hantemirov and Shiyatov 2002.) The idea (promoted by Gavin Schmidt and others) that the Khadyta River site was somehow inappropriate was not argued by Briffa himself.
The impression that I get is that the living samples are, for the most part taken to the south of the subfossil samples. For example, subfossil samples from the Tanlova River are used, but there are no corresponding living samples (and the subfossil sites appear to be north of the present treeline.)
In criticizing my analysis of last fall, Briffa observed:
So what is the “best” indication of relative ring-width changes in this Yamal region? One approach is to judge this by making use of all the data to hand.
A chronology using only the recent data from either POR or YAD will exhibit a greater 20th century increase in growth than one based on JAH, but one based only on KHAD, as in McIntyre’s experiment, is the most anomalous and, therefore, arguably the least defensible. With no additional information with which to justify the exclusion of any of these data, we have produced a chronology using the measurements from all 4 sites
Briffa’s concept of “all the data to hand” is remarkably constricted. There are a number of other chronologies in the region besides the ones mentioned in Briffa’s response. These include a Khadyta spruce chronology, larch and spruce chronologies at Polar Urals, a spruce chronology at Shchunya River, larch and spruce chronologies at Nadim River and Kheygi River (to the southeast).
It is obvious from a simple inspection that the “decline” also affects Yamal chronologies – the elevated growth of the POR-YAD sites in the late 20th century contrasts sharply with the late 20th century decline characteristic of other sites, especially the spruce chronologies. Briffa is obviously not unaware of the “divergence” problem, but the problem is not addressed in either of his journal articles discussing Yamal or in his internet article – the latter is unfortunately preoccupied with trying to “get” the same answer as before, as opposed to reflecting on the more general problem.
This inconsistency is an important statistical issue for users of the Yamal chronology – which include most multiproxy reconstructions. It does seem odd that these few trees, like Graybill’s stripbark bristlecones, are have a unique ability to act as hemispheric thermometers. They deserve to be recognized by UNESCO as sacred groves. It’s too bad that Oxburgh didn’t include that as one of his recommendations.