Comments on McIntyre’s claims on Briffa
Posted by Ari Jokimäki on October 2, 2009
Those who have followed climate science online have undoubtedly heard about recent claims made by McIntyre about Briffa et al. work on tree ring based reconstructions. Keith Briffa has already responded, and RealClimate has also responded. In addition to these, I have couple of things I would like to point out.
McIntyre started the claims in this post. I’ll quote the first sentence from there:
A few days ago, I became aware that the long-sought Yamal measurement data url had materialized at Briffa’s website – after many years of effort on my part and nearly 10 years after its original use in Briffa (2000).
Note that McIntyre doesn’t give a link to Briffa’s website where Briffa introduces the data, but McIntyre links directly (and only) to the page containing the data. It is of course easy to find it yourself, but it seems to be a common theme in McIntyre’s postings that as little outside information as possible is given. McIntyre also doesn’t give proper reference to Briffa (2000), this has also been left for the reader to find out.
Here is the link to Briffa’s website, where the link to the data page is given:
And the link there leads to more thorough presentation of the data:
There then is the link to the data file McIntyre linked to:
Here is the link and the reference to Briffa (2000):
Briffa, K. R. 2000. Annual climate variability in the Holocene: interpreting the message of ancient trees. Quaternary Science Reviews 19:87-105 (unfortunately this paper doesn’t seem to be freely available online).
Now, looking at Briffa’s website and McIntyre’s quote above, I note that there’s something strange here. McIntyre mentions Briffa (2000) and how it’s been 10 years from that, but there is entirely different paper being given in Briffa’s website:
Briffa et al., 2008 Phil. Trans. R. Soc. B, vol. 363, no. 1501, 2269-2282, “Trends in recent temperature and radial tree growth spanning 2000 years across northwest Eurasia” (click “full text” links on the right to read the whole paper).
So, already the first sentence of McIntyre’s post was false. This is not the data for Briffa (2000) (even if a version of it was used there), but it is the data for Briffa et al. (2008). Briffa et al. (2008) is not discussed by McIntyre, but is mentioned once in the caption of Figure 1:
Figure 1. Comparison of the (smoothed) Yamal reconstruction (Briffa 2000, Briffa et al 2008, Kaufman et al 2009 and many others) to the Polar Urals Update (Esper et al 2002).
It is quite ironic that McIntyre’s Figure 1 only contains two curves, “Briffa (2000)” and “Esper update”. I also wonder what exactly is this “(smoothed) Yamal reconstruction” as McIntyre seems to use only raw data (or at least doesn’t say otherwise) from Briffa et al. (2008). Also, again no proper references for any of the mentioned papers.
So, the data is from Briffa et al. (2008). That means we have to consult Briffa et al. (2008) in order to see what has been the data selection process (which McIntyre didn’t do). On Yamal data, they say:
Siberian larch (Larix sibirica) data from the area immediately east of the northern Ural Mountains, previously used by Hantemirov & Shiyatov (2002), were used as the Yamal regional chronology,…
So, it appears they use data from Hantemirov & Shiyatov (2002). Here is the link to that paper (but not freely accessible for everyone):
Hantemirov & Shiyatov, 2002, The Holocene, Vol. 12, No. 6, 717-726, “A continuous multimillennial ring-width chronology in Yamal, northwestern Siberia”
Curiously enough, McIntyre starts discussing Hantemirov & Shiyatov (2002) paper, and I think he shows that he is not aware that Briffa et al. (2008) used the data of Hantemirov & Shiyatov (2002), McIntyre says:
There is one other version of these series that readers may encounter: Hantemirov and Shiyatov archived a Yamal reconstruction at NCDC that has no hockey stick blade whatever. This version was promoted by a commenter (Lucy Skywalker) at Jeff Id’s as being a priori more valid than Briffa’s. Although the Hantemirov and Briffa chronologies have a very different visual appearance (especially the non_HSness of the Hantemirov version), there is an extremely high correlation between the very different looking Hantemirov-Shiyatov and Briffa Yamal chronologies. (If you regress the Briffa recon against the Hantemirov recon for the pre-1800 version, you get a huge r^2 of 0.81). The two series clearly have the same raw material.
That would go without saying, if McIntyre would have looked at Briffa et al. (2008), where he got the data from.