First here is Dr. Keith Briffa’s response in entirety direct from his 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.
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.
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.
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.
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.
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.
Sponsored IT training links:
Guaranteed success in NS0-154 exam with help of 650-177 practice test and up to date 642-515 exam dumps.
Where is his explanation for hiding the data for years?
Where is anything beyond a bland dismissal?
And it is clear from the way he frames the issue that they are not interested in seeing what the trees say. They are out to prove their conclusions.
As said before, they are carving data to fabricate a hockey stick.
Stone-age analysis methods lead to stonewalling.
Well come on you all:
We all commented the silence of the Team was deafening. Briffa has to release something in the genre “his work against my word I did not do it”, regardless how weak. On one hand they always criticize Steve for the lack of peer reviewed publications but here Briffa retreates behind his work not yet published…
Again the next piece of puzzle will come once the raw Temperature data used for HADCRUT will be released. The stonewalling of data release is disheartening: imagine withholding financial data from IRA or CRA and claim you did not evade taxes…
Quote:
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.
Although YAD061 looks like an outlier, the other trees do show a rise from ~1820 to today [albeit smaller] so the record [based on those threes] does not look entirely flat to me.
REPLY: Indeed they do, but what is the cause? Logging making less nearby competing trees for sunlight? A reindeer herd that starts frequenting the area providing more fertilizer? Change in streamflow nearby due to a storm, resulting in a change to the local water table? There could be hundreds of reasons besides climatic temperature change. As I pointed out in this post:
http://wattsupwiththat.com/2009/09/28/a-look-at-treemometers-and-tree-ring-growth/
There are many limiting growth factors all working in concert. It only takes a change in one to change the growth of the tree.
– Anthony
I believe what Dr. Briffa is telling is the truth.
He is just not telling all of the truth.
doesn’t say much really if you ask me
Ah, so he’s a victim of Russian disinfo.
“Do I believe Dr. Keith Briffa? No.”
Same here !!
RC has made a statement/post.
Not buying it.
“Received inappropriote low weight” = “didn’t recieved the heavy weighting I gave it to get the HS shape”
“He offers no justification for excluding the original data;”
Can Briffa justify excluding the dozens of chronologies in the first place?
FYI About Tom P., his post on Realclimate:
“3Tom P says:
1 October 2009 at 9:56 AM
Reports of the death of Biffra’s hockey stick have been much exaggerated.
Steve McIntyre actually dealt the deathblow to his own analysis when he graphed the live tree data in the Briffa/H&S set with his preferred Schweingruber alternative. McIntyre’s alternative was dominated by trees much too short to detect any centennial trend, as I pointed out to him.
Here is what I hope is close to the final exchange at Climate Audit, for the benefit of those who don’t visit often:
Steve McIntyre:
“However, I disagree that the trees in the CRU archive are “much longer-lived”, other than the trees selected for the modern comparison.”
Tom P:
“But the modern comparison was the subject of your original sensitivity analysis that was supposed to have broken the Yamal hockeystick!
“All you have done is inject noise into the Biffra/H&S series by adding in much shorter lived trees. This also explains why the Schweingruber series did not well correlate with the instrumental temperature.”
I wonder how Steve is now feeling with all the attention he is getting. Hubris might describe it.”
“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.”
Thanks for that. In the name of science and the people, who refuses to be traped in these kind of “scientists”.
It’s a remarkable turn around that he deigns to respond at all; a sign of serious stuff hitting big fans in the UK, I expect. And even then, he gives no answer to all the questions we have.
1) Dr. Briffa deserves some credit for making a measured response and acknowledging that the issues have been raised given the intensity of the response generated by McIntyre’s devastating posts.
2) With respect to the charge of cherry-picking I find Dr. Briffa’s response incomplete at best: “…methods that are capable of expressing robust evidence of climate changes using tree-ring data” does not exclude the possibility of simply redefining methods and massaging algorithms until the set that produces the most PC results can be identified and deployed.
Where the bulk of available raw data does not show a particular pattern, any method of filtering, weighting, selection (whatever) that winds up with a ringing affirmation of a politically charged hypothesis is inherently suspect. Unless and until those “methods” are disclosed in detail and justified, the presumption of bias is overwhelming. Set against the background of Mann’s record (including the utterly silly recent hurricane hockey stick) it looks pretty bad.
Oh dear. My first pass at YAD061 and I’m pretty gobsmacked. The entire record comes down to this one tree, more or less. What a revelation! We must go and hug it.
As a repost to Briffa, I quote Briffa:
He offers no justification for excluding the original data
Real Climate comes to the defense of their Team member…
“The statement from Keith Briffa clearly describes the background to these studies and categorically refutes McIntyre’s accusations. Does that mean that the existing Yamal chronology is sacrosanct? Not at all – all of the these proxy records are subject to revision with the addition of new (relevant) data and whether the records change significantly as a function of that isn’t going to be clear until it’s done.”
Yet the rest of the post is all about ad hominem
“What is objectionable is the conflation of technical criticism with unsupported, unjustified and unverified accusations of scientific misconduct. Steve McIntyre keeps insisting that he should be treated like a professional. But how professional is it to continue to slander scientists with vague insinuations and spin made-up tales of perfidy out of the whole cloth instead of submitting his work for peer-review? He continues to take absolutely no responsibility for the ridiculous fantasies and exaggerations that his supporters broadcast, apparently being happy to bask in their acclaim rather than correct any of the misrepresentations he has engendered. If he wants to make a change, he has a clear choice; to continue to play Don Quixote for the peanut gallery or to produce something constructive that is actually worthy of publication.”
Nothing about withholding data for almost 10 years… just “There is nothing wrong with people putting together new chronologies of tree rings or testing the robustness of previous results to updated data or new methodologies.”
Updated data? 10 years?… Yeah right.
Thou protest too much realclimate…
RE: San Antonio,
I renew my concern that Tom P is a foot soldier in the PR battle, sent in by Real Climate and Fenton Communications, and is not someone seeking the truth.
Briffa casts doubt on McIntyre’s methods but says nothing to explain his own. He used a different statistical method–that does not explain using a subset of the trees. If SM has to explain why he used 34 trees from one site in place of the 10/12 trees from varying sites, Briffa needs to explain why he used 10/12 trees rather than the hundreds that are available covering those multiple sites.
Another gem: “Having said that, it does appear that McIntyre did not directly instigate any of the ludicrous extrapolations of his supposed findings highlighted above, though he clearly set the ball rolling. No doubt he has written to the National Review and the Telegraph and Anthony Watts to clarify their mistakes and we’re confident that the corrections will appear any day now…. Oh yes.”
Indeed, the proper way is to do the calculation, submit it to Realclimate, wait for their answer and wait for their answer… another 10 years and meanwhile shhhh, not a word, you enemy of science!
The response wasn’t so much a rebuttal as an indication that a rebuttal will be forthcoming.
Then this isn’t really a response to Steve McIntyre’s analysis, but a general response to the fact that his work is under attack.
No doubt TomP. is here to confuse the message…
One of the questions which Dr. Briffa is NOT answering or even proposing an explantion for is WHY would there be such a marked “outlier” in YAD061.
In fact the general “noise” of the system is so strong, I tend to think of the value for spotting “trends” as “minimal”.
I’m continuously amazed that NONE of these “fine qualified scientists” puts ERROR BOUNDS on their data. That they NEVER do basic statistical analysis to find out their “confidence intervals”.
If I presented this sort of analysis for some of the “Statistical Process Control” work I have done in the past, I would be FIRED, period.
You can’t control to 3 or 6 sigma, if you have no idea what sigma is.