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.
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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?
PR Guy
It does not matter who the messenger is.
Keep the focus on the data.
Bring it on.
“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?
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.
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.)
“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!
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
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.
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?
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.
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]
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.
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.
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.
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.
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]
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.
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!!!!
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.
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.