the Air Vent

Because the world needs another opinion

Briffa Responds

Posted by Jeff Id on October 1, 2009

I’m certain we’ll be hearing more on this today.  This post is copied from a link here.It is a comment from Keith Briffa regarding Steve McIntyre’s recent findings on tree ring data.  The most interesting thing he said was that the Yamal data was NOT pre-sorted according to climate data.  He appears to take offense at the suggestion even though it is standard practice in much of Mannian paleoclimatology.

In addition, he claims his data is the same as the H & S data with different standardizations.  Paper is here. I don’t know a darn thing about corridor standardization but I can infer some detail after my recent study of the Briffa standardization.  On the surface, it seems impossible that standardization might flatten the data to the extent expressed in H & S but we’ll have to wait and see.  There are some points in here which seem to misrepresent reality however, and lead me to wonder what will be said next. i.e. He offers no justification for excluding the original data

Sounds kind of familiar doesn’t it.

I also wonder what he means by unusually high summer temps, there isn’t anything in McIntyre’s statement supporting or denying anything about temperature (my bold in his comment).  Not one comment I recall from Steve. And I’ve seen the temp graphs and there doesn’t seem to be any evidence of unusually high summer temps either.  It’s a distraction which is difficult for me to grasp in the context of reality, as though it is meant to discredit McIntyre while supporting the unprecedentedness of global warming.


Steve’s reply to Briffa.


The Yamal ring-width chronology of Briffa (2000)

My attention has been drawn to a comment by Steve McIntyre on the Climate Audit website relating to the pattern of radial tree growth displayed in the ring-width chronology “Yamal” that I first published in Briffa (2000). The substantive implication of McIntyre’s comment (made explicitly in subsequent postings by others) is that the recent data that make up this chronology (i.e. the ring-width measurements from living trees) were purposely selected by me from among a larger available data set, specifically because they exhibited recent growth increases.

This is not the case. The Yamal tree-ring chronology (see also Briffa and Osborn 2002, Briffa et al. 2008) was based on the application of a tree-ring processing method applied to the same set of composite sub-fossil and living-tree ring-width measurements provided to me by Rashit Hantemirov and Stepan Shiyatov which forms the basis of a chronology they published (Hantemirov and Shiyatov 2002). In their work they traditionally applied a data processing method (corridor standardisation) that does not preserve evidence of long timescale growth changes. My application of the Regional Curve Standardisation method to these same data was intended to better represent the multi-decadal to centennial growth variations necessary to infer the longer-term variability in average summer temperatures in the Yamal region: to provide a direct comparison with the chronology produced by Hantemirov and Shiyatov.

These authors state that their data (derived mainly from measurements of relic wood dating back over more than 2,000 years) included 17 ring-width series derived from living trees that were between 200-400 years old. These recent data included measurements from at least 3 different locations in the Yamal region. In his piece, McIntyre replaces a number (12) of these original measurement series with more data (34 series) from a single location (not one of the above) within the Yamal region, at which the trees apparently do not show the same overall growth increase registered in our data.

The basis for McIntyre’s selection of which of our (i.e. Hantemirov and Shiyatov’s) data to exclude and which to use in replacement is not clear but his version of the chronology shows lower relative growth in recent decades than is displayed in my original chronology. He offers no justification for excluding the original data; and in one version of the chronology where he retains them, he appears to give them inappropriate low weights. I note that McIntyre qualifies the presentation of his version(s) of the chronology by reference to a number of valid points that require further investigation. Subsequent postings appear to pay no heed to these caveats. Whether the McIntyre version is any more robust a representation of regional tree growth in Yamal than my original, remains to be established.

My colleagues and I are working to develop methods that are capable of expressing robust evidence of climate changes using tree-ring data. We do not select tree-core samples based on comparison with climate data. Chronologies are constructed independently and are subsequently compared with climate data to measure the association and quantify the reliability of using the tree-ring data as a proxy for temperature variations.

We have not yet had a chance to explore the details of McIntyre’s analysis or its implication for temperature reconstruction at Yamal but we have done considerably more analyses exploring chronology production and temperature calibration that have relevance to this issue but they are not yet published. I do not believe that McIntyre’s preliminary post provides sufficient evidence to doubt the reality of unusually high summer temperatures in the last decades of the 20th century.

We will expand on this initial comment on the McIntyre posting when we have had a chance to review the details of his work.

K.R. Briffa
30 Sept 2009

  • Briffa, K. R. 2000. Annual climate variability in the Holocene: interpreting the message of ancient trees. Quaternary Science Reviews 19:87-105.
  • Briffa, K. R., and T. J. Osborn. 2002. Paleoclimate – Blowing hot and cold. Science 295:2227-2228.
  • Briffa, K. R., V. V. Shishov, T. M. Melvin, E. A. Vaganov, H. Grudd, R. M. Hantemirov, M. Eronen, and M. M. Naurzbaev. 2008. Trends in recent temperature and radial tree growth spanning 2000 years across northwest Eurasia. Philosophical Transactions of the Royal Society B-Biological Sciences 363:2271-2284.
  • Hantemirov, R. M., and S. G. Shiyatov. 2002. A continuous multimillennial ring-width chronology in Yamal, northwestern Siberia. Holocene 12:717-726.

15 Responses to “Briffa Responds”

  1. Bob H. said

    I posted this comment over on CA, but it is relevent here as well…

    I did a quick search of “corridor standardisation” (also “corridor standardization”) and came up with basically nothing, at least as referring to a statistical method. On the other hand, “Regional Curve Standardization” yielded a lot of hits, mostly by CRU but some independent sources as well, including an abstract from EMS Annual Meeting Vol. 6, EMS2009-20,2009 titled “Shortcoming in the tree-ring regional curve standardization and an improvement of the method.” See the link below

  2. I think Steve’s just this minute got server problems again.

  3. Harold Vance said

    No matter how you slice or dice the response, the gist of the treemometrician’s argument is that growth equals temperature:

    “his version of the chronology shows lower relative growth in recent decades than is displayed in my original chronology.”

    Given the large number of factors (in all sorts of permutations) that can and do affect plant growth, it is astonishing that any scientist could flatly claim that they have controlled for all of these factors over periods of hundreds if not thousands of years with any reasonable degree of confidence. This has to be the biggest inside joke in science today.

  4. Jeff Id said

    #3 I couldn’t agree more. That’s why you don’t see many comments from me about the deeper meaning of these scribbles.

  5. Harold Vance said

    The last point that I would like to make is that even if one does manage to control the factors (or vectors or whatever you want to call them) that affect growth, then the final product (the transformation) is still the equivalent of hearsay.

    Note also that the IPCC presentation of data (the spaghetti graph) is flawed as it mixes fact with hearsay. The facts should be displayed first and the hearsay second and on a separate page. Any presentation that is purported to be factual should NEVER include hearsay, such as temperature estimates based on tree rings.

  6. j ferguson said

    Bender, in one of his comments at CA, suggested that the GCMs would be unaffected by any of this. Do not the modelers expect their models to track historical time series and if Briffa and so on is the best they have to work with, wouldn’t the models be unrepresentative if the time series are?

  7. Antonio San said

    The RC post is invoking how their research is unfairly tared and feathered by the “denialist” blogs… yet every time a paper is published the MSMedia are all over it, worldwide, interviewing the scientist and spinning it in most alarmist ways. I guess this doesn’t count…

    And of course my comment about Tamino’s rant never made it at RC… Yeah, no respected climatology lab could ever dare to question the robustness of their work:

    “Re: #44 Tamino

    “Do you really believe that? Do you think, if all data from every study for all time were freely and easily available, that would have stopped McIntyre from useless unfounded FUD? Or even slowed him down?

    I don’t.”

    Perhaps then instead of Steve McIntyre you fulminate about, it would have been a well respected climatology laboratory independently testing the robustness of these proxies the same year the papers were published…”

  8. Antonio San said

    OT: This reminds me about the fims of Micheal Moore, deswcribed as “small indie productions”… that you can find even in the local grocery market store in a remote small provincial town in France… LOL

  9. Bob H. said

    Apparently the “typical” Larch tree has a lifespan of 100 to 150 years, although I suspect the far north climate may shorten that a fair amount. While I was trying to find a typical lifespan for Larch, I ran across a 900-year Larch chronology from approximately the same area as Yamal. It didn’t perform a temperature reconstruction, but did establish a good correlation between their study and the Polar Urals and Yamal, stating “Archaeological wood from the Ust-Voykar settlement
    was used to build a 903-year-long larch chronology. The
    sample replication and high correlation between series
    make this chronology of high enough quality for consideration
    of possible climatic reconstruction.” See the link below:

  10. Jeff Id said

    #6 I’m not experienced enough with GCM’s to have an opinion. Sorry.

  11. FrancisT said

    Bob H (1 & 9) The H&S paper seems (as far as I can tel) to use extremely long lived trees. They took a buttload of cores and then selected only the really long lived trees.

    Contrariwise Briffa seems to have picked a number of younger cores – but by no means all the data as I explain in my thoughts on Briffa’s response

    PS I have a comment in the RC moderation Q I’m not hopeful

  12. Kondealer said

    Jeff, I’m sure that you will be interested in some recent correspondence I have had with Jan Esper (of Hockey Team Fame).
    Of course my email was “tongue in cheek”, but I was astonished by;
    a) the courtesy of
    b) the naivety of the reply. See below (XXXXXX my self-censorship).

    > Dear Dr. Esper,
    > I am currently teaching a module called “Biomeasurement” (basic
    > statistics)
    > to a group of first year Environmental Science undergraduates and
    > would be honoured if you would agree, in principle (we can sort out
    > detailed arrangements later), to give a guest lecture here explaining
    > the latest developments in Climate Science and some of the exciting
    > methods of data analysis pioneered by you and co-workers.
    > In particular they are keen (as am I) to hear about the techniques you
    > helped develop in paleoclimatology, where the ability to pick and
    > choose which samples to use is an advantage unique to
    > dendroclimatology.
    > All the best,
    > Dr. XXXXXX,
    > Deputy Head,
    > Life Sciences

    Dear Dr. XXXXX, I am just moving into a new position in Germany (whit a much increased teaching load…). So, while generally interested — thanks for approaching me (!) — I would wait another
    1-2 years before signing up for additional lectures (also should add that I just became father of twin babies, which didn’t necessarily relax life for now). If you are not aware of this, there are some true experts on the issue at CRU including Tim Osborn, for example. Best wishes –Jan E.

  13. Kondealer said

    And my questions to Briffa (cc Jones)

    Dear Professor Briffa, my apologies for contacting you directly, particularly since I hear that you are unwell.
    However the recent release of tree ring data by CRU has prompted much discussion and indeed disquiet about the methodology and conclusions of a number of key papers by you and co-workers.

    As an environmental plant physiologist, I have followed the long debate starting with Mann et al (1998) and through to Kaufman et al (2009).
    As time has progressed I have found myself more concerned with the whole scientific basis of dendroclimatology. In particular;
    1) The appropriateness of the statistical analyses employed
    2) The reliance on the same small datasets in these multiple studies
    3) The concept of “teleconnection” by which certain trees respond to the “Global Temperature Field”, rather than local climate
    4) The assumption that tree ring width and density are related to temperature in a linear manner.

    Whilst I would not describe myself as an expert statistician, I do use inferential statistics routinely for both research and teaching and find difficulty in understanding the statistical rationale in these papers.

    As a plant physiologist I can say without hesitation that points 3 and 4 do not agree with the accepted science.

    There is a saying that “extraordinary claims require extraordinary proof”.

    Given the scientific, political and economic importance of these papers, further detailed explanation is urgently required.

    Yours sincerely,

  14. Kondealer said

    Jeff, I think Briffa’s reference to “the unusually high summer temperatures in the last decades of the 20th century” is meant to mean that these trees have responded to increased “degree-days” by growth increases.

    This is intenable on a number of reasons, some plant physiological;

    1)8-sigma increases are simply unbelievable. Van’t Hoff’s rule states that a biological process approximately doubles for each 10C rise in the physiological range
    2) No evidence presented of LOCAL summer temperature increases. Any advance on a 30C increase?

    and some statistical- as Steve M has so ably shown.

  15. Sharpshooter said

    I’m seeing so many parallels with the abuse James Randi and Martin Gardner encountered when analyzing and reporting the ESP and Faith Healer crowds.

    Frauds, fakes and charlatans detest those shedding light on their follies.

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