Before continuing with Yamal, I’m going to make a little detour through the Avam-Taimyr series, the measurement data to which was also archived at the same time as the Yamal data. Taimyr, also originating in Briffa 2000, has been another staple of Team reconstructions in the past 10 years, but doesn’t have a HS pattern. Actually it had a noticeable Divergence Problem, with a 20th century peak in 1942.
While Yamal stayed unchanged in Briffa et al 2008, the Taimyr series was modified noticeably, becoming the “Avam-Taimyr” series. To the previous Taimyr site (72N, 101E), Briffa added the Bol’shoi Avam site (70 30N 93E), about 8 degrees (!) to the west. 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.
Figure 1. Top – Taimyr chronology from Briffa 2000; midde- Avam-Taimyr chronology from Briffa et al 2008; bottom – difference. All series smoothed.
CRU’s archived measurement data set for Avam-Taimyr contains 330 series, more than the total reported in the two original publication. The total number of series in this data set is (much larger than Yamal, especially in the current portion: it has 113 series in 1990, as compared to only 10 at Yamal, and 34 in 1996 as compared to 4 at Yamal. The original Taimyr publication (Naurzbaev et al, Holocene 2002) reports the use of 138 samples – see their Table 2- yielding a chronology from -456 to 2000. The cited Avam publication (Sidorova et al, Russ J Ecology 2007) reports the use of 81 series, yielding a chronology from 886 to 2003.
Annoyingly, there is absolutely NO metadata on the locations of the samples, not even information on which tree belongs to which site -ven though the sites are about 400 km apart. However, a little information can be gleaned from the IDs, together with the above scraps.
The Avam article reports data for years up to 2003, while the latest year in the Taimyr reference is 1996; conversely, Taimyr has data prior to 886, whereas this is absent from Avam.
Identifying first series ending after 2000, a total of 12 series is obtained, all starting with the prefixes “bav” or “pp”. Next isolating trees with these prefixes, a total of 107 cores (about one-third of the collection) – but more than 81 tree noted in Sidorova et al 2007 for Avam. Hmmm.
The second criterion yields 60 series, of which three start with the prefix “MAY”, 56 with the prefix “KTU” and one with the prefix “K” (which might be a typo for KTU, but this doesn’t matter.) Table 1 of Naurzbaev et al includes IDs for sample for which radiocarbon dates were obtained – including IDs with prefixes, KTU and MAY (as well as the prefix NOV) also occurring in the CRU data set. In total, the prefixes MAY, KTU and NOV pertain to Taimyr, this identifies 103 cores as coming from Taimyr, leaving about one-third still unallocated. (As noted above, 138 series were reported as being used in the chronology – some of which would precede the CRU start date of -207). (A further 29 cores have 3-letter prefixes – XAT (Khatanga?) and KAM – perhaps reconciling somewhat to the 138 series mentioned in Naurzbaev et al (or perhaps not.)
42 of the 120 still unallocated series had IDs of the form 011011 to 011232. Next I looked at ID formats for archived ITRDB sites within 10 degrees or so of Avam and Taimyr. This yielded some immediate dividents. The Schweingruber site, Balschaya Kamenka (russ124w), located at 71 20N 93 50E (nearer Avam than Taimyr) had IDs exactly matching these 42 series. So this Schweingruber data had been included in the mix. (There’s a reason for this parsing, which we’ll come to with Yamal – so be patient).
There is another Schweingruber larch series at the same latitude located closer to Taimyr that were not included in the compilation: Aykali River (russ094) at 69 32N, 97 32E. Plus there is a Schweingruber site almost contiguous to Taimyr: Novaja Rieja (russ080) at 72 27N, 101 45E and two Schweingruber series at Kotuyka River (russ024, russ165) at 104 E. It’s hard to see a rational reason for including Balschaya Kamenka (russ124w), but not the others.
For now, I merely note that, for a series that had a Divergence Problem rather than HS shape, Briffa 2008 did not merely leave this series alone (as they did with Yamal), but added in measurements from up to 400 km away.
For the chronology calculation, as far as I can tell (and I’ll report on this replication), one growth curve was then applied to all the measurements (regardless of location), yielding the new Avam-Taimyr RCS chronology.