Posted on 10/01/2009 8:29:06 AM PDT by Thickman
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.
Thanks. That is amazing! The story gets more and more interesting every hour.
He concludes:
“while it takes years to produce your data despite repeated requests, you can mount a response to Steve McIntyres findings on that data in a couple of days, through illness even.”
Your comments are appreciated by me... You who know science and its publication procedures better than me. On my own I would have seen Briffa’s response as being reasonable
I’ve heard and read material by McIntyre for years but Briffa, never heard of him until a few days ago with this new flap which shows how devious some of the global waring contingent is. I would say grant money had made them into liars_at_any_price
Someone once warned about this very thing.
BFLR
Not only does extra co2 cause extra growth, but cooler but wetter years can cause more growth than warm but dry. It’s a real tricky thing to use tree rings as a proxy for temperature. I thought that was one of the things brought up in controversy with the Mann hockey stick curve.
We would do well to remember what President Eisenhower said.
It appears that this response can be boiled down to: “I am not a crook.”
This is all about the ‘hockey stick,’ this current debate is on the latest version; but one of the original arguments about the first such graph was that using similar processes and selecting time frames was that any data could be made to show a hockey-stick shape; now, today in realclimate Gavin Schmidt gleefully demonstrates the technique:
http://www.realclimate.org/index.php/archives/2009/09/hey-ya-mal/#more-1184
If not, and my understanding is this sample was not randomly selected at all, then he is toast. At least a dozen major studies will need to be revised which used his COOKED data (not his raw data but even that was cooked by selection bias but would have been rejected by honest researchers).
There are simply not a large number of trees around the world showing hockey stick cores. If there were a majority of randomly selected cores with the shape, that would be significant. But in this (formerly) prime hockey stick location, there isn't. There is essentially ONE tree with a pure hockey stick shape. The rest peak before the time of coring.
“BFLR”
That’s a new one for me.
Oops. That would be “bump for later reading”.
Am I (or you) qualified to pass judgment on what's been said so far? Clearly this won't shake out in a day or so. I think it's pointless to try and judge the state of a particular (peculiar) branch of climate science based on back-and-forth blog postigs that have been generated in a month or less. If McIntyre thinks he's got something, truly and seriously, he needs to publish it -- and it will get published. Dialogue in the blogosphere won't cut it if this if this is truly a scientific problem.
Look at what happened when there was a close examination of the recent paper by McLean, deFreitas, and Carter. Rebuttals were in press within a month (and they had some questionable statistics, too). McIntyre knows statistics, and he can publish. He has before. If this is a serious problem with a lot of papers that needs to be fixed, and he's the guy that can show why, he needs to -- that's way that scientists do it. If he doesn't publish, why should the IPCC notice him?
I've read the responses here and the ilk are so misled by the level of importance this constitutes -- if it's even a problem at all. Right now it's a prosecutorial opening statement, and now we've heard the defense's opening. Let the trial begin -- in the court of science. No matter what I think of the issue, the process is fun to watch.
Except for one thing; if this turns out to be a tempest in a teapot, and not a case of scientific misconduct OR a serious flaw in the basic scientific understanding of how Earth's climate works -- will the skeptical sites that started this ball rolling try to push it back up the hill? Will they apologize to the people they've misled, and particularly to the reputation of scientists they've maligned? I don't know -- and there may actually be a case of scientific misconduct or malpractice -- or at least really bad methodology -- here. Either way, someone is going to have to take the blame for something.
By the way, I accidentally found the link below, and wondered if you'd seen it. I actually haven't had a chance to read it, but I promise to (by next Monday). I just think it's definitely a subject you're interested in.
Briffa is talking about points that McIntyre raised himself! I didn't even pick up on that until someone else pointed it out and I went back and readk McIntyre's originals.
Subsequent postings appear to pay no heed to these caveats. Briffa's basically pointing out that McIntyre stopped paying attention to his own original statements of uncertainty.
The expert reports upheld all of our criticisms of the Mann Hockey Stick, both of the mathematics and of its reliance on flawed bristlecone pine data. One of the panels, however, argued that while the Mann Hockey Stick itself was flawed, a series of other studies published since 1998 had similar shapes, thus providing support for the view that the late 20th century is unusually warm. The IPCC also made this argument in its 2007 report. But the second expert panel, led by statistician Edward Wegman, pointed out that the other studies are not independent. They are written by the same small circle of authors, only the names are in different orders, and they reuse the same few data climate proxy series over and over.Perhaps this is what Schmidt was referring to. If so, he's only drawing attention to what has been very publicly rebuked. He's obviously getting very desperate. Here's another good drubbing with some good graphs and the famous "Back to graduate school, Gavin" post by Henk Tennekes. Here's another critique of the same sort by DAleo.
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