Briffa’s Avam-Taimyr Series

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.

References:
Naurzbaev (Holocene 2002) url
Sidorova et al (Russ J Ecology 2007) url

6 Comments

  1. Peter Dunford
    Posted Sep 27, 2009 at 4:41 AM | Permalink | Reply

    In principle this is no different to the way GissTemp works: if something doesn’t look right, fix it with data from somewhere that does, or make some data up. It’s all good climate science.

  2. tty
    Posted Sep 27, 2009 at 5:04 AM | Permalink | Reply

    Shouldn’t be “Taimyr” rather than “Taymir”? Nit-picking I know, but when citing an appendix to a book rather than an appendix to a chapter in the same book can make reviewer have hysterics, one can’t be too careful.

    • Steve McIntyre
      Posted Sep 29, 2009 at 5:53 AM | Permalink | Reply

      Re: tty (#2),

      At the risk of hijacking my own thread, I think my misspelling “Taymir” is a curious sort of Freudian slip. One of our friends is a Scottish immigrant to Toronto (as opposed to long-term Scottish diaspora like me) and is fond of bad poetry (and good) poetry. McGonagall, recognized in some quarters as the author of the “worst poem” in the English language is one of his favorites. And the highlights of the McGonagall opus are the Silvery Bridge over the River Tay and The Tay Bridge Disaster, the latter generally conceded to hold a more special place.

      An excerpt from the first poem:

      Beautiful Railway Bridge of the Silvery Tay !
      And prosperity to Messrs Bouche and Grothe,
      The famous engineers of the present day,
      Who have succeeded in erecting the Railway
      Bridge of the Silvery Tay,
      Which stands unequalled to be seen
      Near by Dundee and the Magdalen Green.

      and of the second:

      I must now conclude my lay
      By telling the world fearlessly without the least dismay,
      That your central girders would not have given way,
      At least many sensible men do say,
      Had they been supported on each side with buttresses,
      At least many sensible men confesses,

      However, I think that McGonagall’s undoubted triumphs are easily surpassed by a poet of the Scottish Diaspora in Ontario, one whose name conjures up lyric images (I mean, of course,….. James McIntyre), whose most famous poem commences:

      We have seen thee, queen of cheese,
      Lying quietly at your ease,
      Gently fanned by evening breeze,
      Thy fair form no flies dare seize.

      McGonagall’s corpus is said to include the following:

      His unparalleled awkward rhythms and dud rhymes were perfectly matched by his subject matter: spectacular train wrecks and the mountains of Greenland.

      I have not examined McGonagall’s corpus in detail. Both topics – the Arctic mountains of Greenland and train wrecks – are highly topical in paleoclimate.

      • Jean S
        Posted Sep 29, 2009 at 6:31 AM | Permalink | Reply

        Re: Steve McIntyre (#7),
        Hijacking this back to the original topic ;), I was wondering if you have tried how “robust” Figure 8 (“the moving window Kendall’s W”) of Briffa et al is for this Avam-Taimyr (and other) modification? They make rather strong statements based on the curves (once again, unnecessary smoothing used but that’s different story) such as (my bold)

        In the unsmoothed data, relatively high concordance is apparent again in medieval times, but the highest values in 2000 years are recorded for windows spanning the most recent century or so. In figure 8b, concordance is calculated for different length windows using the raw RCS indices, but the results for each window length are smoothed (using the negative exponential least-squares method; Mclain 1974), which is roughly equivalent to using a 200-year spline. In the unsmoothed concordance series, except for the shortest (51 years) window results which clearly show high concordance approximately 900, there is evidence of rising and unprecedented similarity in tree growth across northwest Eurasia in the most recent century. This is accentuated in the smoothed series for 101- and 201-year window lengths.

        The statement is made despite the fact that 51-year window has diverged from the other two windows, and is about to drop below the “significance level” (dashed line) … This “result” is given already in the abstract as follows (my bold)

        Using Kendall’s concordance, we quantify the time-dependent relationship between growth trends of the long chronologies as a group. This provides strong evidence that the extent of recent widespread warming across northwest Eurasia, with respect to 100- to 200-year trends, is unprecedented in the last 2000 years.

        Somehow, I’m reminded about Mann’s “robust” “evolving multivariate correlations” :)

  3. tty
    Posted Sep 27, 2009 at 5:45 AM | Permalink | Reply

    Bol’shoi Avam is clearly the odd man out here, since it is situated at c. 200 meters altitude in a narrow valley deep in the Putorana Mountains, and probably has a considerably different local climate than the other sites which are in lowland forest (c. 50 m altitude).

  4. Posted Oct 1, 2009 at 11:00 AM | Permalink | Reply

    Bol’shoi Avam is clearly the odd man out here, since it is situated at c. 200 meters altitude in a narrow valley deep in the Putorana Mountains, and probably has a considerably different local climate than the other sites which are in lowland forest

    R.Burlow
    owner of website –> Billiard Table Dimensions

8 Trackbacks

  1. [...] 8. Faced with a sample in the Taymir chronology that likely had 3-4 times as many series as the Yamal chronology, Briffa added in data from other researchers’ samples taken at the Avam site, some 400 km away. He also used data from the Schweingruber sampling program circa 1990, also taken about 400 km from Taymir. Regardless of the merits or otherwise of pooling samples from such disparate locations, this establishes a precedent where Briffa added a Schweingruber site to provide additional samples. This, incidentally, ramped up the hockey-stickness of the (now Avam-) Taymir chronology. http://www.climateaudit.org/?p=7158 [...]

  2. [...] 8. Faced with a sample in the Taymir chronology that likely had 3-4 times as many series as the Yamal chronology, Briffa added in data from other researchers’ samples taken at the Avam site, some 400 km away. He also used data from the Schweingruber sampling program circa 1990, also taken about 400 km from Taymir. Regardless of the merits or otherwise of pooling samples from such disparate locations, this establishes a precedent where Briffa added a Schweingruber site to provide additional samples. This, incidentally, ramped up the hockey-stickness of the (now Avam-) Taymir chronology. http://www.climateaudit.org/?p=7158 [...]

  3. [...] picked from a larger population – measurements from the larger population remain unavailable. One post ago, I observed that Briffa had supplemented the Taymir data set (which had a pronounced 20th century [...]

  4. [...] were picked from a larger population – measurements from the larger population remain unavailable. One post ago, I observed that Briffa had supplemented the Taimyr data set (which had a pronounced 20th century [...]

  5. By The Siberian Tree-Ring Circus « the Air Vent on Sep 29, 2009 at 11:25 AM

    [...] is an attempt at a non-staistical explanation of work done by Steve McIntyre (especially here, here and here) and Ross McKitrick, all credit belongs there not here – Update (29 Sept) The key final [...]

  6. By Kylmää vettä MOT:n niskaan « Gaia on Nov 8, 2009 at 10:36 PM

    [...] http://www.climateaudit.org/?p=7158 [...]

  7. [...] picked from a larger population – measurements from the larger population remain unavailable. One post ago, I observed that Briffa had supplemented the Taimyr data set (which had a pronounced 20th century [...]

  8. [...] picked from a larger population – measurements from the larger population remain unavailable. One post ago, I observed that Briffa had supplemented the Taimyr data set (which had a pronounced 20th century [...]

Post a Comment

Required fields are marked *

*
*

Follow

Get every new post delivered to your Inbox.

Join 3,184 other followers

%d bloggers like this: