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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“My colleagues and I are working to develop methods that are capable of expressing robust evidence of climate changes using tree-ring data.”
One cannot legitimately change the method of analysis on such noisy data and then release the results showing only the final analysis. The method of analysis has to be defined before the data is analyzed. To change the analysis method after playing with the data allows the analysis method used to be “cherry picked” to achieve the desired result. If one must change the analysis method, then do so, lock the analysis, and then go get new data to see if the result is the same. And, of course, test the new analysis against red noise random number sets.
A common scam in epidemiology is to check a small population for an unusual incidence of hundred of diseases and then only report that a specific disease has a high incidence in this small population. This is exactly what was done with the power line scam. Hundreds of diseases were checked and then only the results for power lines and leukemia were reported because that had a high incidence in the small population used. Faulty conclusion: living near power lines caused leukemia. The same data analysis showed that power lines prevented pancreatic cancer. Both were BS, (bad statistics).
If Briffa wants to present a new analysis of the old data, do not allow him to get away with it. It will not mean anything until the exact same new analysis is used on tree ring data that has not yet been measured. I will not trust any new analysis from Briffa that comes from archived data that he has had a chance to test before disclosing the new analysis method.
“Re: #44 Tamino
“Do you really believe that? Do you think, if all data from every study for all time were freely and easily available, that would have stopped McIntyre from useless unfounded FUD? Or even slowed him down?
I don’t.”
My reply:
Perhaps then instead of Steve McIntyre you fulminate about, it would have been a well respected climatology laboratory independently testing the robustness of these proxies the same year the papers were published…
What is the significance of this statement by Briffa?
“In their work they traditionally applied a data processing method (corridor standardisation) that does not preserve evidence of long timescale growth changes.”
“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”.
“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.
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.
Mike Bryant (10:24:25) :
Look… I am a plumber… can someone please explain how the tree ring data can override the existing arctic temperature records? It seems to me that this alone puts the lie to the Yamal hockey stick… Like I said… I’m a plumber… what am I missing here??
Mike Bryant
If you tested toilet water would you say all the water in the house is dirty?
The “experiment” is dirty.
In laymans language, his sample size is much too small.
If you run a small sample size, throw out the extreems.
His sample is not random.
Blind studies are much better. Another poster mentioned separation of people by reason of the experimentor should not have acces to the trees or material gathered.
An independent audit is how much of the world works.
Leif Svalgaard (09:36:45) :
“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?”
Exactly the point, except that “those trees” are being used to support AGW climate change, where the jist of what I take a way from all of this is that “those trees” aren’t worth bumpkus as a temperature proxy. The real nexus of McIntyre’s work/attention is that anyone with a valid scientific hypothesis should never be afraid of someone else looking at their basic data. All else aside, regardless of the apparent reality of a postulated hypothesis, if a scientist appears unwilling (or is willing) to release their raw data and basic data selection and alaytical methods, it must invariably lead to suspicion of the veracity of their results.
So a couple of trees, and it might even be the one is what defined Climate History?
Please someone tell me this is a bad dream i am on.
Any of this farceants, clowns have the gal to call himself scientists?
What he said was that he didn’t cherry pick; if any cherry picking occurred, it was H&S wot dun it.
“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).”
So his claim is basically that he simply reprocessed all the records H&S gave him.
I had understood from Steve McIntyre’s post that this was not so: “while the CRU archive does not appear to be the precisely the same as the unavailable Hantemirov and Shiyatov 2002 archive, it does appear to be related.” However, he also says “It is highly possible and even probable that the CRU selection is derived from a prior selection of old trees described in Hantemirov and Shiyatov 2002 as follows:” and the following quote includes the line “These were the longest and most sensitive series, where sensitivity is measured by the magnitude of interannual variability.” which would therefore be the selection criteria.
Thus, the implication of this is that, yes, they were cherrypicked for “sensitivity”, but that it was Hantemirov and Shiyatov that made the selection, not Briffa. Steve’s criticism is that Briffa should have realised that this made them unsuitable for application of RCS.
So I’d say Briffa has a point. But don’t forget this bit: “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.” I think that counts as acknowledgement that Steve McIntyre might have a point; which is probably as much as could be expected from the team.
In all of this discussion, it is interesting to me that tree growth as a proxy for climate change automatically equates to a change in temperature. Briffa’s reconstruction becomes a hot button issue under those circumstances. But the climate change that could be relevant to this proxy is the concentration of atmospheric gases. Plants like CO2 – they grow better, they become more drought tolerant, etc. It doesn’t have to be that a herd of reindeer fertilized the trees. It could be that we did. And that might correlate nicely with the apparent growth increase starting in the 1800’s noted by Leif, and takes care of the apparent paradox of older trees experiencing a late stage growth spurt.
Putting Briffa and Tom P.’s posts together leads me to think you’re missing Briffa’s point, Anthony.
Let me quote from McIntyre’s original post:
“Perhaps the difference between the two versions is related to different aging patterns in the Schweingruber population as compared to the CRU population. The CRU population consists, on average, of older trees than the Schweingruber population. It is highly possible and even probable that the CRU selection is derived from a prior selection of old trees described in Hantemirov and Shiyatov 2002 as follows:
In one approach to constructing a mean chronology, 224 individual series of subfossil larches were selected. These were the longest and most sensitive series, where sensitivity is measured by the magnitude of interannual variability. These data were supplemented by the addition of 17 ring-width series, from 200–400 year old living larches.
The subfossil collection does not have the same bias towards older trees. Perhaps the biased selection of older trees an unintentional bias, when combined with the RCS method. This bias would not have similarly affected the “corridor method” used by Hantemirov and Shiyatov themselves, since this method which did not preserve centennial-scale variability and Hantemirov and Shiyatov would not have been concerned about potential bias introduced by how their cores were selected on a RCS chronology method that they themselves were not using.
Briffa’s own caveats on RCS methodology warn against inhomogeneities, but, notwithstanding these warnings, his initial use of this subset in Briffa 2000 may well have been done without fully thinking through the very limited size and potential unrepresentativeness of the 12 cores. Briffa 2000 presented this chronology in passing and it was never properly published in any journal article.”
Seems to me like Briffa is acknowledging in passing that he intentionally selected longer-lived trees and is defending his choice of exponential normalization, which may cause the most recent tree-rings from the living trees to show an exaggerated warming signal.
I don’t know if there’s some justification for using only longer-lived trees. As McIntyre pointed out, the subfossil larches don’t have the same bias. Maybe any selection of long-lived trees would create an artificial hockey stick.
If the longer-lived trees bias was valid for the living trees, it should have been a valid criterion for the subfossil record. If adding short-lived trees to the recent parts of the record just adds noise and hides the real variability, adding short-lived trees in the subfossil record also adds noise and hides the real variability.
If the longer-lived trees bias was valid, he needed more cores anyway. If he didn’t have enough cores for a good sample, he shouldn’t have published.
hmmmm (10:01:51) : and others
I’d guess because people want to replicate the damned study and keep getting stonewalled.
It would seem that the effort should be directed towards the general utility of trees. If it can be shown they are no good [“hundreds of other reasons”], then the various stonewalling etc doesn’t matter anyway.
More fun than Dan Rather’s memos, also I recall, at the start of a hockey season.
Same, same. So convinced they are of their theory, they willingly and uncritically accept any old BS evidence to support it.
The proof of cherry picking may never be had short of a lie detector test, but it is not too soon to compare the memos to the hockey stick and YAD061 – of which Briffa must surely have been aware – and place them both in a special class of evidence.
A class somewhat less reliable than jailhouse snitch testimony.
Guys, I should be seeing Glenn Beck tonight. He is in my area to promote his book. I will pass this on. I can’t wait to tell him that global warming is caused by one quirky tree.
I mean what do you know. Global Warming is caused by humans, just not the way they said it was.
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.
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.
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.
But what is the most important? In other words, which factor is more significant in tree ring growth? (Caveat: I can supply (time is at a premium just now) additional papers showing similar responses, it was cherry picked because the authors put it most eloquently.)
Articles
Ecology
Response of tree-ring width to rainfall gradient along the Tianshan Mountains of northwestern China
Sang WeiGuo 1 , Wang YunXia 2, 3, Su HongXin 1 and Lu ZhaoHua 2, 4
(1) Key Laboratory of Vegetation and Environment Change, Institute of Botany, Chinese Academy of Sciences, Beijing, 100093, China
(2) Institute of Restoration Ecology, China University of Mining & Technology in Beijing, Beijing, 100083, China
(3) Mathematics & Physics Unit, Beijing Officers’ School of Armed Forces, Beijing, 100012, China
(4) Binzhou College, Binzhou, 256600, China
Received: 29 May 2007 Accepted: 5 September 2007
Abstract By comparing the long-term tree-ring growths at various geographic scales, we can make clear the effects of environmental variations on tree growth, and get an understanding of the responses of forest ecosystems to the possible changes in global and regional climate. Radial tree-ring growth of Picea schrenkiana and its relationship to air temperature and precipitation were investigated across longitude transects on the north slopes of the Tianshan Mountains in northwestern China. Tree-ring samples were collected and residual chronologies were developed for three different regions along a gradient of decreasing precipitation from west to east. Response-function analysis was conducted to quantify the relationships between tree-ring chronologies and climate variables, such as monthly mean temperature and monthly precipitation from 1961 to 1998, using the PRECON software program. The statistical characteristics of the chronologies showed that the three chronologies constructed in this study contained significant environmental signals and were well suitable to reveal the impacts of climatic change on tree growth and forest productivity. Annual ring-width variations were similar among the three sites, but the variability was greatest in the east. This research showed that the growth trends of Picea schrenkiana in the Tianshan Mountains have not followed a uniform pattern. Response-function analysis indicated that there were significant correlations between tree growth and climatic factors in all the three regions, among which precipitation was the principal. With decreasing precipitation, the response of tree-ring widths to increasing temperature changed from a positive to a negative correlation. As for precipitation, the positive relationship to tree-ring width always dominates. It could be expected that with increased temperature and decreased precipitation, the importance of precipitation to three growth would increase, and the response of tree growth to environmental changes would also increase. This study emphasizes the importance of regional-scale investigations into the biosphere-climate interactions. The results of this research indicated a substantial increment of tree-ring radial growth as a result of warmer and wetter climate in the eastern regions. However, climate change will have less effect on forest growth and primary production in the western regions.
Leif Svalgaard (09:36:45) :
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?
Leif : Get real. You become most perturbed when people develop inaccurate conclusions from data, and develop associations based on garbage. This is exactly what concerns us (maybe it’s just me) in this matter. These hockey sticks get a lot of attention in the media, and are used by intellectually deficient policy makers to justify taxation. The ignorant masses believe that the conclusions drawn by the authors of this paper indicate that current temps are much higher, which is categorically incorrect according to the station records. I could care less whether it’s slightly warmer globally than X (any date). But the statistical contortions leading to erroneous conclusions drawn from a few scrawny trees really [snip] me off. These people have no concept of any facet of plant physiology.
Gary (09:55:37) :
I agree. Briffa has posted a response (even if one that leaves me still a bit skeptical) and deserves the appropriate courtesy.
Which I have to say is a lot more than any of use would get if we dared express a heretical opinion at RealClimate.
I still think (no pun intended) that we are in danger of not seeing the wood for the trees. As Anthony points out there could a number of reasons why any individual tree suddenly “goes walkabout” and, as Nylo points out, tree growth is as responsive to CO2 as it is to temperature. If any of what Briffa et al are assigning to temperature is actually the result of CO2 then the AGW argument gets blown even further apart and the whole basis for it crumbles to dust.
It seems to me that we are well into Rumsfeld’s “Unknown Unknowns” territory.
Dr Briffa’s evasion of the salient points suggests that should the fundings plug ever be pulled on CRU (which it deserves to be) he would make a good living as a politician.
(…)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 (…)
this comment shows that tree rings cannot even account for the regional variability of temperature. Imagine this proxy stretched to represent long-term global temperature trends
CA is responding again. Like a snail maybe, but at least it’s alive.
McIntyre has a post up with Briffa’s reply and his rebuttal.
http://www.realclimate.org/index.php/archives/2009/09/hey-ya-mal/
Here is my comment on that thread:
————————————————————
RC Group,
I am mad at you! (grin)
When this story first broke at CA and WUWT I posted on WUWT that Mann et al. (2008) reproduced the hockey stick with and without tree rings and that all of the data and supporting materials were free to download. I thought that that was pretty clearly the death blow to the CA controversy. Of course, the thing just took off at WUWT.
So, I have spent the past several days and many hours working on a reply that was similar to this thread but, of course, you guys beat me to it and did a much better job than I could ever have done.
I will say that in my brief research, I think boreholes look very promising as perhaps the best temperature proxy.
Huang, S. (2009). Brief introduction to the geothermal approach of climate reconstruction. Retrieved September 20, 2009 from Borehole Temperature and Climate Reconstruction Database: http://www.geo.lsa.umich.edu/climate/approach.html
Huang, S. P., H. N. Pollack, and P.-Y. Shen (2008). A late quaternary climate reconstruction based on borehole heat flux data, borehole temperature data, and the instrumental record, Geophys. Res. Lett., 35, L13703, doi:10.1029/2008GL034187.
Pollock, H. (2005, December). Reconstruction of ground surface temperature history from borehole temperature profiles. Retrieved September 29, 2009, from http://home.badc.rl.ac.uk/mjuckes/mitrie_files/docs/mitrie_borehole.pdf
————————————————————
This whole thing reminds me of the OJ Simpson case where there was massive evidence against him (including the revelation from his own attorneys that he miserably failed two polygraphs) but the case was decided by “If the glove don’t fit, you must acquit” and convincing the jury that hundreds of people conspired to plant evidence at the crime scene and in a hotel room, and then at the lab, etc., etc. etc.
What bothers me the most about this story and appears to be a running theme here at WUWT is that somehow there is this massive conspiracy among scientists to delude the public for no other reason than we do not wish to look wrong. We certainly are not getting rich by taking the pro-AGW position. It is just silly.
Hasn’t anybody here wondered why the hockey stick shape keeps appearing regardless of proxy and study author? Perhaps it is a real phenomenon? To suggest that it isn’t implies that scientists are colluding or that every proxy analysis technique always results in the same shape. If so, then why bother trying to understand the past?
I think many people are misinterpreting this very important sentence: “My colleagues and I are working to develop methods that are capable of expressing robust evidence of climate changes using tree-ring data.” I interpret that to be an admission that present methods are not robust, an interpretation shared by Jennifer Marohasy.
I think the source of the misinterpretation has been the illicit change from the use of the term ‘global warming’ to the term ‘climate change’ yet keeping the onus on CO2 as the cause of ‘climate change’ as the alarmists are wont to do. Interpreted more conventionally and literally, all he is saying is that he is trying to capture the true voice of the dendro record, as it sings its duet of growth and temperature.
===========================================
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.