Response from Briffa on the Yamal tree ring affair – plus rebuttal
This is going to be a major scientific scandal, I think.
1
10
2009
First here is Dr. Keith Briffa’s response in entirety direct from his CRU web page:
Dr. Keith Briffa of the Hadley Climate Research Unit - early undated photo from CRU web page
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.
Dr. Keith Briffa in 2007 from this CRU web page: cru.uea.ac.uk
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.
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Now a few points of my own:
1. Plotting the entire Hantemirov and Shiyatov data set, as I’ve done here, shows it to be almost flat not only in the late 20th century, but through much of its period.
Zoomed to last 50 years - click for larger image
How do you explain why your small set of 10 trees shows a late 20th century spike while the majority of Hantemirov and Shiyatov data does not? You write in your rebuttal:
“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.”
Justify your own method of selecting 10 trees out of a much larger data set. You’ve failed to do that. That’s the million dollar question.
Briffa Writes: “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.“
OK Fair enough, but why not do it for the entire data set, why only a small subset?
2. It appears that your results are heavily influenced by a single tree, as Steve McIntyre has just demonstrated here.
wattsupwiththat.files.wordpress.com
10 CRU trees ending in 1990. Age-adjusted index.
As McIntyre points out: “YAD061 reaches 8 sigma and is the most influential tree in the world.”
Seems like an outlier to me when you have one tree that can skew the entire climate record. Explain yourself on why you failed to catch this.
You really should click on the link above and look at the individual tree charts.
3. Why the hell did you wait 10 years to release the data? You did yourself no favors by deferring reasonable requests to archive data to enable replication. It was only when you became backed into a corner by The Royal Society that you made the data available. Your delays and roadblocks (such as providing an antique data format of the punched card era), plus refusing to provide metadata says more about your integrity than the data itself. Your actions make it appear that you did not want to release the data at all. Your actions are not consistent with the actions of the vast majority of scientists worldwide when asked for data for replication purposes. Making data available on paper publication for replication is the basis of proper science, which is why The Royal Society called you to task.
Read about it here
Yet while it takes years to produce your data despite repeated requests, you can mount a response to Steve McIntyre’s findings on that data in a couple of days, through illness even.
Do I believe Dr. Keith Briffa? No.
wattsupwiththat.com
From the comments:
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CodeTech (09:13:47) :
Quote:
My colleagues and I are working to develop methods that are capable of expressing robust evidence of climate changes using tree-ring data
Mr. Briffa, I need read no further.
You have now explained yourself, and your goal. That goal has nothing to do with Science, or the discovery of truth, it is only the mundane, self-serving goal of proving your pet theory.
Shame on you, and your colleagues.
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PR Guy (09:46:58) :
Re: Frank Stembridge
Many in the press (who should know better) do not realize or choose not to recognize that they are being manipulated by PR flacks and that Real Climate is simply a production of a PR firm. (Fenton Communications) My comments are intended for them.
I support your assertion that this audience should continue to focus on the data.
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Jeff (10:01:24) :
“My colleagues and I are working to develop methods that are capable of expressing robust evidence of climate changes using tree-ring data.”
I caught that too. As a scientist, I’m appalled at such a statement. I was reading through a stats book this morning and ran across the following: “Scientists often hope passionately that a particular experimental result will turn out to be statistically significant, so that they can have a paper published in Nature and get promoted, but that doesn’t make it right.” – Michael J. Crawley, Imperial College, London.
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Richard M (10:03:02) :
I read through the RealClimate response. They are very, very worried. You could tell that in their attack on SM. Steve has been very careful in saying we need to get a response from Briffa (it’s the comments that have been harsh). RC in their haste to post something, have made themselves out as complete fools. By attacking Steve they have done the exact thing they are complaining about. This is what people do when they are not thinking very well.
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10
2009
Michael (10:03:34) :
I’m trying to put this whole mess in a nut shell for the sheeple.
So let me see if I get this straight.
Michael Mann’s cherry picked ice core data that produced the infamous hockey stick graph, correlated with Keith Briffa’s cherry picked bristlecone pines tree ring data that confirmed the sharp rise in global temperatures noted on the hockey stick graph, both of which by the way have now been discredited, was the basis for forming public policy decisions that have a grave affect on all of mankind.
Can this statement be improved?
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Lucy Skywalker (10:13:59) :
“In 1961, a 27-year-old assistant professor of psychology, Stanley Milgram, wanted to study obedience to authority…” He found that, under pressure from the experimental scientists, 65% would administer electrical shocks they had been told were lethal (although they were not). Milgram was hounded out of Academia for this research – a case of “shoot the messenger” I think. In fact, all participants were debriefed, it seems debriefed perfectly well, and several were positively grateful what they had learned, and changed as a result. From “Opening Skinner’s Box” by Lauren Slater.
The most vulnerable to this kind of behaviour were people who were normally gentle and kind, and just wanted to be liked. Mavericks were far more likely to refuse to participate.
I needed to understand all this, to grasp what had happened when just such an individual, for whom I had had a lot of respect, turned my own life upside-down because I didn’t fit his “authority”. I see the same face in Briffa, both young (here) and current (at Jennifer Marohasy). Trying to please. I feel sorry for the man. But am I right?
I still want the truth out re Climate Science.
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DennisA (10:35:18) :
“My colleagues and I are working to develop methods that are capable of expressing robust evidence of climate changes using tree-ring data”:
This is the classic “interrogating the data until it confesses”.
1
10
2009
Michael (10:35:57) :
“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.”
And there’s the admission.
1
10
2009
W. Earl Allen (10:36:34) :
Here’s the most relevant sentence from RC’s “rebuttal” of McIntyre:
“People have written theses about how to construct tree ring chronologies in order to avoid end-member effects and preserve as much of the climate signal as possible.”
And what “climate signal” are we looking for? This GavinSentence is about as clear a reference to the cherry picking methods of the hockey stick Team as has ever been written.
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t-bird (10:55:32) :
To a layman this is a frightening story. That global energy policy could be determined by one guy in a micro-specialty using a nano-view of the world is outrageous. (Of course, it bears similarity to Ancel Keys’ work, too, so I guess it’s not a new phenomenon.)
Funny that global warming is so alarming and so extraordinarily obvious that it only shows up in ONE tree in one grove in remote Siberia.
Please, carry on. The stakes are high.
1
10
2009
Jeremy (10:56:35) :
Clearly, reading tree rings is dead.
Dr Briffa et al. may be remembered for single-handedly managing to destroy what little credibility this scientific activity originaly held. I feel sorry for other researchers who are now unlikely to get time of day from anyone for their analyses. The plot of those 10 trees tells me ONE thing – no honest scientist in their right mind would knowingly combine that data and try to pass it off as science in respected journal. Obviously the choice of the indvidual tress in the data set – one tree more or one tree less – will have HUGE impact on the results and Dr. Briffa HAD to have known that. This is NOT science!
I suggest Dr Briffa finds something else to do – reading tea leaves or astrological signs perhaps.
1
10
2009
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OceanTwo (11:14:43) :
To be honest, I’m pretty mad about this. This data and what it represents is one of the fundamental sources of anything and everything global warming.
Every single action that the AGW ivory elites push is based on the hockey stick data. But the most infuriating thing is that these elites solution does nothing but take away from people and give to others (”We are all gonna die!!….But for a small sacrifice by you of only a gazillion dollars, your first born, and say, your right leg, everything will be juuuust fine…”). Any actual solutions proposed can already be done today (wind power, solar cells, electric cars, and so on), which tells us it’s not about those things at all.
These ’scientists’ (The Group? Who is this self appointed ‘group’, anyway?) are simply determining the best way to research and present data to further their agenda, exemplified the statement:
“My colleagues and I are working to develop methods that are capable of expressing robust evidence of climate changes using tree-ring data.”
One would hope that this was a statement written with little thought – evidence of climate change(s)? This is like saying that we are looking to find ‘robust evidence’ of the moon revolving around the earth. Climate…changes. The Climate Change/Global Warming euphemism is bitch, sometimes.
It seems like the AGW crowd and the self-appointed IPCC are pontificating around a sinking lifeboat, blaming the people actually rowing for their woes.
Gah, it’s just infuriating.
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Doug in Seattle (11:27:56) :
As a lead author of the IPCC report, Dr. Briffa refused to provide independent reviewers with access to the data upon which he and others were issuing strong statements about the robustness of their conclusion that the warming of the 20th century was unprecedented.
Now that the data has been released and is criticized as being anything but robust, he fesses up and says he and his colleagues are working on making it more robust.
Sorry, I don’t buy it.
I also have a problem with his assertion that he did not pre-select his data – it implies a level of naivety that does not fit with his position as leading expert in his field. Or perhaps I am being naive in assuming that such a renowned expert would be aware of methods which ensure that bias does not contaminate a dataset.
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