Response from Briffa on the Yamal tree ring affair – plus rebuttal

First here is Dr. Keith Briffa’s response in entirety direct from his CRU web page:

Dr_Keith_Briffa

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

Dr. Keith Briffa in 2007 from this CRU web page: http://www.cru.uea.ac.uk/cru/people/photo/keith2007b.jpg

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.

Yamal-Hantemirov-Shiyatov-0_2000_zoomed2

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.

Briffa_single_tree_YAD061

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.

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.


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hunter

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.

John S.

Stone-age analysis methods lead to stonewalling.

Antonio San

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…

CodeTech

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.

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

FerdinandAkin

I believe what Dr. Briffa is telling is the truth.
He is just not telling all of the truth.

Richie

doesn’t say much really if you ask me

SteveSadlov

Ah, so he’s a victim of Russian disinfo.

“Do I believe Dr. Keith Briffa? No.”
Same here !!

RC has made a statement/post.

MattN

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?

Antonio San

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.”

PJMM

“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”.

Robert Wood

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.

George Tobin

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.

Robinson

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.

Robert Wood

As a repost to Briffa, I quote Briffa:
He offers no justification for excluding the original data

Antonio San

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…

PR Guy

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.

Tom

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.

Antonio San

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!

Phil

The response wasn’t so much a rebuttal as an indication that a rebuttal will be forthcoming.

We have not yet had a chance to explore the details of McIntyre’s analysis or its implication for temperature reconstruction at Yamal…

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.

Antonio San

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.

Antonio San

The Group Team: “Peer-review is nothing sinister and not part of some global conspiracy, but instead it is the process by which people are forced to match their rhetoric to their actual results. You can’t generally get away with imprecise suggestions that something might matter for the bigger picture without actually showing that it does. It does matter whether something ‘matters’, otherwise you might as well be correcting spelling mistakes for all the impact it will have.
So go on Steve, surprise us.”
As long as the reviewers are part of the Team, there is no problem with the peer review process… LOL

It’s hard to make sense of the statement, but it seems he has sidestepped the critical questions.
Does he agree that he made use of some data but not other data?
If so, why?

Frank Stembridge

PR Guy
It does not matter who the messenger is.
Keep the focus on the data.
Bring it on.

gianmarco

“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.”
really says it all. in fact, they are looking for a connection temperature-CO2 and using any possible mean to validate it.
i am by no means an expert, but i have read several papers, and i found an interesting concept in a few of them, the “instrumental paradox”.
do instuments agree with ringree in the 20th century? some papers i read say they dont.

Leif Svalgaard (09:14:03) :
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:[…]There could be hundreds of reasons besides climatic temperature change.

So why the fascination with those trees in the first place? If there can be so many reasons besides climate changes, why get all hot under the collar about something that apparently is a poor indicator?

Robin

I can tell flannel and stonewalling when I see it. Here in Briffa’s response it is all too clearly demonstrated. Anthony’s follow up questions and observations are right on the money and Briffa should respond without delay.

gianmarco

i work in IT and one of the rules of software engineering is to never let the designer test their own code. they will usually design tests that will carefully avoid to find the bugs, and more often than not they do it honestly.
they simply use the same thought process to write the code and to test it. and they wont see the bugs even when in front of massive evidence.
i am not expecting the hockey team to acknowledge errors any time soon. i just hope the MSM and politicians will notice the broken stick. i am not holding my breath though.

hunter (09:02:16) : “Where is his explanation for hiding the data for years?”
He could probably come up with something, I’m sure, but this looks really, really bad, given that it comes down mostly to just one tree. He should face the music and withdraw the original paper right now, without further lost time wasted squirming. He has other results to publish. Let’s see them, as soon as possible, instead of a list of excuses, rationalizations, and evasions. Be a mensch, Keith!
“Where is anything beyond a bland dismissal?”
Actually, it’s in there if you read carefully. You might easily miss it. And he provided a nifty bibliography which I wish I’d had two days ago. Be well, Keith.
“And it is clear from the way he frames the issue that they are not interested in seeing what the trees say.”
He certainly implies something close to: We are developing methods to make trees talk. (…and they’ll say what we want them to, and nothing else? That’s called dendrophrenology.)

Sam the Skeptic

“My colleagues and I are working to develop methods … robust evidence …”
Anyone who has lived in the UK for the last decade will recognise all the symptoms of Nu-Labour speak in this statement. It’s meaningless and, as CodeTech points out, it assumes its own answer!

Corey

My colleagues and I are working to develop methods that are capable of expressing robust evidence of climate changes using tree-ring data

I think he already did that, and look how it turned out.

Briffa’s statement is the beginning of the end. And it seems he might not be that ill… BTW, don’t bother to comment on RC; comments are being blocked.
Ecotretas

PR Guy

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. My comments are intended for them.
I support your assertion that this audience should continue to focus on the data.

Steinar Midtskogen

In my opinion, the hockey stick seems odd not because of the recent temperature increase, during which period we have pretty good direct measurements, but that it shows a remarkable stable climate prior to the 20th century. So if the Yamal tree rings are all about 20th century, how does that change the hockey stick? How does that change the supposedly dead calm climate prior to the modern era?

Bob Koss

Briffa is still hiding pertinent information.
“was based on the application of a tree-ring processing method”
No mention of what that method entailed. I suggest the method used was a method that selects based on showing the greatest deviation toward warming.

Jim

This is just too humerous to not pass on.
From the discussion at (un)Realclimate:
8
FredB says:
1 October 2009 at 10:13 AM
If you want to cut McIntyre’s feet out from under him then all you have to do is release the raw data and the processing code. Until you do this he will always appear to have a convincing case.
I really can’t see why you don’t undertake this simple and devastating step.
[Response: All of the data and models for any of our recent papers are online and downloadable by anyone. You must have us confused with someone else. – gavin]

P Wilson

Sam the Skeptic (09:43:02)
As a UK citizen I can confirm that the RMS Titanic did not sink in 1912. This is because when I was at Brighton I dipped my foot into the sea and didn’t feel a signal, a mast, a portal or anything.
Actually this sort of British reasoning was written up by Bertand Russel in his book “The scientific outlook” where he argued that scientific technique would be sequestrated by the minority to keep the majority in relative ignorance.

Privet Ein

Desperate damage control over at RC. I bet not a single objective comment will not make it past the mods today which does not tow their line.
At least people are waking up to their unaccountable practice.

geo

Outliers are not a big problem IF the sample size is large enough, but of course here it isn’t. If you’re going to use small samples you really need to trim the outliers off both edges.
Arguing that there was warming in the late 20th century even without the outlier misses the point. I don’t know anyone serious who thinks there was wasn’t warming in the late 20th century. It’s the hockey stick blade “straight for the sky” kind of warming that is being tussled over here.

David Segesta

The graphs other than YAD061 do show an upward trend but most of the increase seems to occur before 1925. However most man made emissions of CO2 occurred after 1925.

othercoast

Instead of the above “no I didn’t” response, the (anonymous) author of
http://www.realclimate.org/index.php/archives/2009/09/hey-ya-mal/
instead lists a number of graphs (more of less describing them to studies or measurement series) that purportedly show hockeysticks of temperature without being based on the Yamal data [snip]
Generally, the point is sarcastically made that you can get hockeysticks everywhere from all sorts of measurements.
Quite how one of the graphs (which appears to show a hockeystick of radiative forcing and/or CO2 rather than temperature) is supposed to support that argument I don’t understand.
But all the others are small unreadable graphs linking to webpages of larger studies that they’re apparently taken from. I went to a few to see what they’re based on (particularly those where a multi-curve graph dies down to 1 curve by the time the hockey stick starts), but I’m not familiar enough to identify them as actually being based on the Yamal [snip] after all (or not).
Not that it would do much good to post a comment there that picks them apart, but It would be interesting if one of the knowledgeable investigators here could dissect their sarcastic list into Yamal uses, other known hockey-stick bases, and other types (such as those with suspect but unreleased data sources).
[snip]

hmmmm

Antonio,
What is the cutoff point for a tree’s age to make it viable (how many years)? and do we have the ages for each of these trees (those that were used in Briffa and those that were discarded)? Please direct me to the location of that information if it is available.
I’m assuming that this is due to the age-correction which seems to be greater at young ages and tends to a constant over time (negative exponential)? I’d love to see how this was determined.
I don’t think the short-lived trees should be discarded though; it’s not just noise in their data. The correction would give them more age-correction error which would make them less effective at being absolute thermometers, but as you know we are looking at the relative changes over years of multiple samples. Although a single short-lived tree might not make a good absolute thermometer, a large collection of short-lived trees over time should still be able to make a good relative thermometer over the years. The age errors should theoretically cancel each other out as sample size increases.
I am no expert though.

MaryAnn

Robinson (09:22:49) :
“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.”
That made my day. Thanks for the laugh!!!!

Gary

OK, regardless of hard feeling about past behaviors, real and imagined to varying degrees on both sides of the argument, let’s be polite and take this as at least a partial effort to engage outstanding and legitimate questions of method and analysis.
Briffa says, “Whether the McIntyre version is any more robust a representation of regional tree growth in Yamal than my original, remains to be established.” Let’s get on with understanding what the trees really can tell us about past climates. Extracting a pound of flesh, as Shylock learned, isn’t without its costs. By all means the debade should be open and rigorous, but this reply has little if any nastiness and ought to be treated fairly.

Chuck L

The “team” has rolled out a vast collection of ice core/C02 hockey sticks, borehole hockey sticks, glacier retreat hockey sticks, Had Crut temp hockey sticks, etc. to counter Steve’s outstanding work. Wouldn’t it be interesting to obtain the data behind these other hockey sticks…
Oh wait, they “lost” the Had Crut raw data.

I have been following the “tree ring kerfuffle” for the past several days with great interest. While I’m neither a statistician nor mathematician (actually a ME), the one thing I have come to believe is that it doesn’t seem that tree rings are a very reliable proxy for determining past temperatures.
Unfortunately the Hockey Team has already inflicted their stick damage, providing the world’s politicians a stick of their own with which to gain yet more power. Those politicians are not about to give up their quest to utilize that stick to gain even more power.
Dr. Briffa’s stonewalling has given the pols the time needed to secure their position. Only a continuation of the cooling trend we’ve experienced over the past few years will cause folks to begin believing their lyin’ eyes once again. We can be assured there will be no support from the main stream media in reporting on the unscientific methods that have been employed by the Hockey Team.