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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Leif Svalgaard (10:51:04) :
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.
The problem, to me is that those trees are the justification for trillions in increased taxes and increased control of the people by their “betters” in government.
I think that we should drop the characterization “cherry picked” and emphasize the need for sample metadata and an explanation of how Briffa (or whomever) selected his 10 or 12 trees from the available pool of trees/cores. I saw the data the same way Lief did: All 10 trees show a warming trend – though YAD06 appears as an outlier in this very small sample. But as I have said elsewhere – without a view of a larger sample one cannot actually say whether YAD06 is an outlier. If the 11th and 12th trees had the same profile as YAD06, then what? I think Steve’s whole argument is that a lack of transparency with respect to data and methods is bad for climate science. Briffa’s Yamal proxy, unfortunately, is a perfect example of poor practice with regards to transparency.
On an earlier post Al The Brit made a point about exaggerated scales on graphs. This especially occurs on graphs showing temperature anomalies. This is on post, please bear with me as it must be read to the end?
To illustrate my last remark :-
1 The eminent Professor George Manley FRGS produced the Central England temperature graphs from 1650 to 1974.
You need to scroll to Page 14 of the pdf to see the hand drawn graph.
Also it may be of some interest to some on this site where he in effect deals with the urban heat island effect regarding monitoring stations around Oxford. Scroll to Page 2.
2 Now have a look at Hadcruts graph of the temperature anomaly a miracle its a Hockey stick graph?
http://hadobs.metoffice.com/hadcet/
You couldn’t make this up or could you?
It would be nice if you could post the graphs for me?
Sorry I forgot the link to Professor Manley’s graph?
http://www.rmets.org/pdf/qj74manley.pdf
Pushing my luck I know please could you insert?
The concept of tree ring growth as a proxy for temperature is an outright [snip] in and of itself. A tree can grow quite well over a rather wide range of temperatures. It regulates the temperature of its leaves or needles to make up for differences of ambient temperature. Other factors then determine the tree growth.
In radio, there is a little thingy called “signal to noise” ratio. Where ambient temperatures are concerned regarding tree rings, it is all noise and no signal.
As a lead author of the IPCC report, Dr. Briffa refused to provide independent reviewers with access to the data upon which he and others were issuing strong statements about the robustness of their conclusion that the warming of the 20th century was unprecedented.
Now that the data has been released and is criticized as being anything but robust, he fesses up and says he and his colleagues are working on making it more robust.
Sorry, I don’t buy it.
I also have a problem with his assertion that he did not pre-select his data – it implies a level of naivety that does not fit with his position as leading expert in his field. Or perhaps I am being naive in assuming that such a renowned expert would be aware of methods which ensure that bias does not contaminate a dataset.
“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 ”
I think this is a warmist strawman. It’s not necessary for there to be a conspiracy for “groupthink” to take place.
“We certainly are not getting rich by taking the pro-AGW position. It is just silly.”
I’m not sure who “we” refers to, but certainly Al Gore is getting rich. In any event, nobody can seriously deny that climatologists are receiving enhanced funding, attention, and prestige as a result of concerns over CAGW.
“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 I can find you 3 proxy temperature records which do not have hockey-stick shapes, will you concede that you are in the wrong?
Well, how do you refute the general utility of trees if you can’t get access to the data and methods used to show that trees do have utility? Can you imagine trying to get a paper published where your reviewers are other dendros, with a lot invested in the technique? It must be very difficult to argue to the contrary and actually get your paper published.
Isn’t tree ring growth influenced much more by things other than temperature? Like maybe water? I would bet you take two near identical trees and water one and leave the other to fend for it’s self, the growth differences would be obvious after a few years.
Yep, I did that, and it worked — Watered trees grow faster.
So how can you even consider tree rings as a proxy for temperature without knowing what their entire environment was? Makes no sense.
Michael (10:03:34) : I’m trying to put this whole mess in a nut shell for the sheeple. So let me see if I get this straight…
Michael, we are all sheeple to some extent… until we go and investigate for ourselves. Do yourself a favour and read BOTH significant pieces by Bishop Hill, starting with Caspar and the Jesus Paper, to help you get your basics right.
The trees noted above appear to end measurement in 1990. If so, this is something of a tempest in a teapot. We all know that recent temps were the highest in the 2000’s (until a couple of years ago). Therefore arguing to 1990 doesn’t seem particularly compelling with respect to the current climate.
However, as the data goes, it shows the 1940’s as the highest or equivalent temp in 7 of the 10 samples, against a general background of warming since 1850 (again, not a contested point).
Is this not a bombshell? Or admission in fact that they do pick tress to fit the AGW?
from RC now:
In his response to McIntyre, Briffa says that “We do not select tree-core samples based on comparison with climate data”.
However I have read in RealClimate, on a post called “A New Take on an Old Millenium” from February 2006, that “They make use only of those proxy records which demonstrate a statistically significant relationship with modern instrumental temperature records”.
How are these two statements true at the same time?
[Response: Because they are talking about different things? The first is associated with which physical tree cores go into a particular chronology (like Yamal) which are composites of hundreds of trees. They do not pick their trees based on what the eventual chronology will look like. The second statement is with respect to a particular question relating to temperatures at multiple sites during the Medieval Climate Anomaly – what would be the point of looking at rainfall proxies? – gavin]
I don’t usually post without reading a thread, so somebody else may have jumped on this whopper, but doesn’t he pretty much admit that he knows what he is looking for before he starts? Isn’t this the very attitude that keeps him from understanding the objections to his work? He is so certain of global warming that he doesn’t even allow for the possibility that it isn’t there. He seems to be admitting that he is searching for ‘rhetorical’ graphs that can be used in propaganda pieces to convince us all of the “Global Warming Conjecture” that they seem to believe is proven by other means?
Scott A. Mandia (11:11:39) ,
in all fairness: O.J. was guilty of the crime, but the police did fabricate evidence because they didn’t have a strong-enough case. What would you want a jury to do, faced with credible evidence that the state had fabricated evidence?
Anyway, I’m not sure in which side you’re referring to in your analogy as the maniacal killer, and which side represents the racist cop.
Wow, it’s down to a single tree? This just gets better and better.
Maybe YAD06 is a “lovely old tree” (Fast Show – BBC TV) and a favourite of the locals and one where they choose to sit and sing around the camp fire of an evening?
Seriously though. I planted about a million trees in Scotland about 25 to 30 years ago, probably 50,000 of them larch. They are all different shapes and sizes now – (I went back and looked). How come that happened? – they have all grown up enjoying the same climate.
No one has mentioned tree roots. I would think a pretty big factor on how a tree grows is its root system, after all that’s where they get their nourishment. Count me in as one of the skeptics when it comes to being able to get a global temperature curve out of a few miniscule pieces of wood cores bored from a few trees in some remote part of Siberia. What happens in the winter when it’s 40 below? Do trees still grow at 40 below? So many questions…
“We certainly are not getting rich by taking the pro-AGW position. It is just silly.” OK, hows about you give us the benefit of the doubt, and tell your warmie friends that we aren’t getting rich by taking skeptical positions either? Would that be too much to ask?
posted @ur momisugly rc:
Two parts of this story do not greatly fill me with confidence. Firstly, most of the convincing temperature proxies seem to only go back a few hundred years. The tree ring chronologies are maybe best placed for cross dating things like tree-line advance – but if recent events have taught us anything, the error bars for a tree-ring temperature reconstruction are large. Other long term proxies seem to differ fairly significantly, so all I’d be certain of for the last 2000 years is ‘not much change.’
The second and more contentious issue is that of the recent instrumental record. CET for this year simply didn’t seem above average to me, and various different recent detailed measurement series seem to offer the potential for divergence (although this probably is more of a wait and see problem).
Scott A. Mandia (11:11:39) :
Given that borehole data reaches back some 500 years, whereas other reconstructions not necessarily including tree rings date back much further, it doesn’t go back sufficiently to record either the holocene optimum, the Roman warm period, or the MWP.
@Mike Bryant
“I’m a plumber and I don’t understand this…..”
Sorry couldn’t resist this:-
Hockey Stick Man:
I’m a lumberjack, and I’m okay.
I sleep all night and I work all day.
The Canadian:
He’s a lumberjack and he’s ok
He sleeps all night and works all day
Hockey Stick Man:
I measure rings on the trees
Some I like and some I leaves
I have some friends who measure with me
Some they like and some they leaves.
The Canadian All togeffer noow:
He measures rings on the trees
Some he likes and some he leaves
He has some friends who measure with him
Some they like and some they leaves.
The end (of my career)
@ur momisugly brazil84 (11:31:48) :
I did not say EVERY reconstruction is a hockey stick. 🙂
BTW, I do not drive a BMW nor do I live in a big house. 🙂
Most of the researchers are just like me regarding demographics. 🙁
REPLY: Not all – check the latest main page story. Too much money flowing around uncontrolled in our government science programs apparently, you’re just on the low end of the totem pole. – A
Leif Svalgaard (09:36:45) :
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?
What an extraordinary and unscientific statement.
What’s your point, Lief?
You got 2 bob each way, do ya?
addendum to last post.
Here’s loehle’s reconstruction based on non treering data
http://tinyurl.com/y8sn45r
Scott A. Mandia (11:11:39) :
Hasn’t anybody here wondered why the hockey stick shape keeps appearing regardless of proxy and study author?
See Tim Clark (10:58:14) :
Not at all. Only why it’s always correlated to temperature. Warmer temps mean greater precipitation. Google again.
>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.”
Patrick, it means that the two papers results are not comparable.
The other method that Briffa refers to is not good at comparing temperatures across centuries. They were instead looking for short term changes in temperature. I think the different methods may have led to Briffa getting bad results for his method, as they did all the data collection to suit their methods.
This is why this data should be made public, so that it can be evaluated.