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« Sliding science | Main | Valuing "subsidies" »

Tree ring proxies RIP

Well, well. Look what Steve McIntyre has found. After all those years of sceptics calling for tree-ring series to be updated so as to provide out-of-sample validation of their effectiveness as proxies, and all those years of mainstream climatologists telling us how this couldn't happen because of the cost and difficulty, one of the key series in the Hockey Stick and many other temperature reconstructions has finally been brought up to date.

The series in question is Sheep Mountain, prominently featured in The Hockey Stick Illusion as having a hockey stick shape, the blade of the stick allegedly tracking the rise in northern hemisphere temperatures up to 1980, the end of the Hockey Stick reconstruction. Since 1980 we had another 18 years of temperature rises followed by a decade and a half of the pause.

So what has been happening to tree rings on Sheep Mountain been doing in that time? As McIntyre explains, we already knew about the first few years, because Donald Graybill, who collected the original data, did so in 1987.

The original Graybill Sheep Mountain chronology ended in 1987 (rather than 1980) and, though little discussed previously, actually declined quite sharply in the 1980s.

And now that hint of problems being swept under the carpet has been brought out into the open. The update, by Salzer et al, comes in the form of two different updates to the Sheep Mountain record - the northern and southern series (NFa and SFa):

The updated Salzer SFa chronology...shows a dramatic decline from the closing values of the series used in Mann et al 1998.  While the Salzer NFa chronology...  is slightly elevated relative to the SFa chronology and to the millenium mean, its values are also much lower than closing MBH98 values of the Graybill chronology. Both diverge dramatically from the NH temperature. To have kept pace, SFa and NFa chronology values ought to have reached nearly 3, while the SFa chronology has almost reverted to the long-term mean, with several recent values actually below the long-term mean. Perhaps this accounted for the interest in looking at north-facing exposure separately.

Yet mainstream science and government scientists will not acknowledge a problem with the hockey stick or with reconstructing temperatures from tree rings.

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Reader Comments (78)

Hide the Decli

Dec 5, 2014 at 11:38 PM | Unregistered Commenterkim

Well, it formatted as a nice reverse hockey stick slope down.

Dec 5, 2014 at 11:40 PM | Unregistered Commenterkim

Jim Bouldin's eloquent series of posts about how difficult it is to use tree rings as temperature proxies has still no tbeen acknowledged by the cognoscenti, let alone rebutted.

Dec 6, 2014 at 12:15 AM | Unregistered Commenterdiogenes

A tree ring chronology is probably a pretty good record of the growth of that particular tree.

Dec 6, 2014 at 2:31 AM | Unregistered CommenterJimmy Haigh

I wrote this a few years ago.


There was a crooked Mann
Who played a crooked trick
And had a crooked plan
To make a crooked stick

By using crooked math
That favored crooked lines
Lysenko's crooked path
Led thru the crooked pines

And all his crooked friends
Applaud what crooked seems
But all that crooked ends
Derives from crooked means

Eugene WR Gallun

Dec 6, 2014 at 3:45 AM | Unregistered CommenterEugene WR Gallun

Rob Wilson: "- more to individuals using one study to vindicate their blind belief that tree-rings cannot be used to reconstruct past temperatures."

My particular blind belief came from Steve Mcintyre's blog, and the NAS recommendation to avoid the use of bristlecone pines. This was reinforced when I read of people "hiding the decline" which I'm assured by the cli sci commuity is a phrase used by scientists to indicate that they're doing something entirely innocent to the data to avoid getting the wrong answer.

Dec 6, 2014 at 4:07 AM | Unregistered Commentergeronimo

Did not the son of one of the UEA scientists demonstrate flaws in this hypothesis on one of the bushes in their own garden? Is there any truth to this story, or is it just that: a story?

Dec 6, 2014 at 10:25 AM | Registered CommenterRadical Rodent

Did I mention "Briffa's Truncation"? A previously undiagnosed communicable disease which makes the viewer of a chart blind to the decline at the end.

Dec 6, 2014 at 10:50 AM | Unregistered Commentergeronimo

Rob Wilson: "- more to individuals using one study to vindicate their blind belief that tree-rings cannot be used to reconstruct past temperatures."

Oh dear yet another "reasonable" climate scientist (Rob) has revealed his true colours when push comes to shove.

Sounds a lot closer to the truth, just slightly reworded
"- more to individuals using one study to vindicate their blind belief that tree-rings can be used to reconstruct past temperatures."

Dec 6, 2014 at 12:33 PM | Unregistered CommenterBitter&Twisted

Dec 6, 2014 at 3:45 AM | Unregistered CommenterEugene WR Gallun


As an occasional contributor of "poetry" here myself, thank you for your "Hockey Stick" above.

Dec 6, 2014 at 1:20 PM | Unregistered CommenterPeter Walsh

Agree PW re EWRG, I remember that bit from before. I've been thinking about how to rework the second stanza. Lysenko was a petty(hee hee) local bit of rough weather; this climate tempest is a global event, world class extreme mess.

Dec 6, 2014 at 2:25 PM | Unregistered Commenterkim

Rob has pointed out that "one swallow does not a summer make," i.e. we would be well not to take one single paper as "proof" of anything. I do wish he'd passed that advice on to his colleagues preparing the Third Assessment Report when they overturned decades of scholarship on the back of a single paper concocted by the self-acclaimed Nobel Prize winner.

Dec 6, 2014 at 5:02 PM | Unregistered Commentergeronimo


No, other proxies do not agree with Dr Mann. It entirely depends on which cherry tree you want to pick from and whether you then turn the cherries upside down or not..

Firstly as regards glacier lengths. Here is a graphic I created showing the advance and retreat of glaciers over the last 3000 years taken from thousands of references from Ladurie and Pfister. On to it has been placed the hockey stick which manages to sail on serenely whilst all around it glaciers advance and retreat

The link below goes to the borehole database held by the University of Michigan.

It shows that bore holes illustrate rising temperatures since 1500. Due to sampling problems I think we are safe to say from 1700 but 1500 seems doubtful. CET shows this 300 year rise as well.

What are we to make of this as Dr Mann shows declining temperatures for the last thousand years until the sudden rise in the last century when he swapped cherries for oranges.

Well, if you would like to look at the borehole data, which is a pretty good proxy for other novel paleo methods it seems you could reconstruct whatever temperature scenario you wanted. Why not have a try?


Dec 6, 2014 at 5:06 PM | Unregistered Commentertonyb

Diogenes points to Jim Bouldin's series of posts on the problems inherent in dendro studies - these posts are an essential identification and (generally) readable summary of the some of the major issues with connecting tree rings / tree growth with temperature.

At the start of his series, he notes:

" Here, I’ll describe what I see as the three most critical issues. It is not an overstatement to say that all long term climatic estimates are suspect due to these (and other) issues. It’s that serious. [...]

The three issues are:

◾(1) ring width, being the result of a biological growth process, almost certainly responds in a unimodal way to temperature (i.e. gradually rising, then rather abruptly falling), and therefore predicting temperature from ring width cannot, by mathematical definition, give a unique solution,
◾(2) the methods used to account for, and remove (“detrend”) that part of the long term trend in ring widths due to changes in tree age/size are ad-hoc curve fitting procedures that cannot reliably discriminate such trends from actual climatic trends, and
◾(3) the methods and metrics used in many studies to calibrate and validate the relationship between temperature and ring response during the instrumental record period, are also frequently faulty.

Each of these issues by itself would be a serious problem, but collectively they render unreliable all long-term estimates of climate change from ring widths. Worse, there are also several other issues that I don’t have time to get into, at least for now."

The series starts here:

He tried but failed to get a paper published in PNAS on these issues, based (he felt) on faulty and uncomprehending reviews. Quelle surprise.

Bouldin is very much an adherent to the standard interpretation of the correlation between modern global warming and CO2. His criticism is of what conclusions, if any, can be drawn from the dendro studies regarding long term climate conditions - which means that efforts to use dendro studies to put modern warming in a historical context are unreliable.

To Rob Wilson's point, the Bouldin posts and analysis suggest very strongly that, regardless of the particular problems with specific chronologies, the entire field is highly suspect. His posts have not received much airing (and he has more or less wandered away from discussing the field in part because he felt no one was interested).

Dec 6, 2014 at 6:47 PM | Unregistered CommenterIan

Rob Wilson

The problem with tree rings remains the same and can never be overcome with sufficient confidence for them to be useful as treemometers.

Tree growth is stimulated by several natural features of our climate. They include water, temperature, CO² partial pressure, leaf litter and animal poo. I have not yet seen, and I do not expect to see, a mathematical model for extracting temperature out of the noise of the other parameters.

I am open to being made to look the fool.

Dec 6, 2014 at 6:47 PM | Unregistered CommenterStephen Richards

Carrick commented at CA with some observations which I find very helpful. I hope I may reproduce his remarks here, since I think he provides an elegant overview of what is wrong with the recent uses (by Michael Mann and many paleos) of proxies for temperature [emphasis added for first quote, from Steve Mc to Nick Stokes, to which Carrick is also responding]. The field of paleoclimate has thus far failed to demonstrate that the science is "self-correcting" because no one within the field seems to be willing/able to learn from Climate Audit and no one seems willing to correct Mann and others with proper refutations and critiques:

Carrick at Climate Audit

"Secondly, the concept of a proxy reconstruction depends on the notion that there is a relationship between hemispheric temperature and gridcell temperatures and that a hemispheric temperature can be plausibly estimated from a relatively limited number of locations. If you dispute this idea, then it would be constructive if you took it up with Phil Jones and reported back to us."

I believe it’s widely accepted by paleoclimatologists that most tree ring proxies don’t simply track temperature. Rather they track multiple climate variables. In deed many of Mann’s proxies are actually precipitation proxies, as he himself acknowledges. So Steve McIntyre really doesn’t need to explain any of this to Mann or to Jones, it’s well known and accepted.

Mann provides a hand-waving argument that temperature can correlate with precipitation followed by a “correlation = causation” by screening by correlation over some fixed period. Testing the validity by comparing his screening results against out of sample data is one way of testing the validity of that screening protocol, which is how we got here right now.

It’s hardly amazing to me that the Sheep Mountain proxies fail to validate in this way because the inclusion of strip barked proxies has already been heavily criticized, and by people “in the know” discounted as unlikely to be valid temperature proxies.

Further it doesn’t amaze me that tree ring proxiesas a class fail as long-period temperature proxies, even if they are truly exhibiting temperature limited growth: I’ve made this argument before on your blog.

We both know that tree-rings do not have a linear relationship with temperature (rather it’s a compressive nonlinearity). Since the climate signal shows a 1/f behavior, this means that small frequencies (long periods) will have larger amplitudes and show more compression than larger frequencies (short periods). Ergo “loss of low frequency information”.

Using the climate signal from trees must involve some method of correcting for loss of low-frequency information. Generally this is done by inclusion of temperature-calibrated proxies like borehole measurements (which are more nearly linear, but suffer from poor temporal resolution). The Moberg2005 method is a good example of this approach (though it has problems of its own).

The trouble with Mann is frankly he’s just not very good at what he does. He’s apparently never either bothered to learn enough signal processing to help him overcome the issues, relying instead on arrogance, intimidation, dishonesty, bullying and even demonizing of people who disagree with him.

Which is why I claim that many of Mann’s supporters are genuinely uninterested in what the true answer to the question of “what does historic climate prior to good surface temperature data look like”. Otherwise there’d be a whole lot less patience within the climate and activity community with Mann’s tactics than there is already. Mann’s big problem is he has friends who support him because of his mouth, rather than support him because of the quality of what he does.

Dec 6, 2014 at 8:16 PM | Registered CommenterSkiphil

Skip hill

I posted borehole themperatures just above your post. They show a steady increase in temperature over hundreds of years but like all proxies have their shortcomings.

Tree rings have been wildly over promoted as a means of estimating temperature. They may have some small merit to determine moisture in their very specific micro climate during the growing season. They tell us nothing of other seasons


Dec 6, 2014 at 8:33 PM | Unregistered CommenterTonyb

All the ancient trees that died in the effort--what of them?

Dec 7, 2014 at 3:25 AM | Unregistered CommenterLarry Sheldon

Dec 6, 2014 at 10:25 AM | Registered CommenterRadical Rodent

Did not the son of one of the UEA scientists demonstrate flaws in this hypothesis on one of the bushes in their own garden? Is there any truth to this story, or is it just that: a story?


It appears to be true :

At 10:03 PM 6/5/2003 -0600, Tom Wigley wrote:

Well put! By chance SB03 may have got some of these precip things right, but we don't
want to give them any way to claim credit.
Also, stationarity is the key. Let me tell you a story. A few years back, my son Eirik
did a tree ring science fair project using trees behind NCAR. He found that widths
correlated with both temp and precip. However, temp and precip also correlate. There is
much other evidence that it is precip that is the driver, and that the temp/width
correlation arises via the temp/precip correlation. Interestingly, the temp correlations
are much more ephemeral, so the complexities conspire to make this linkage
I have not seen any papers in the literature demonstrating this -- but, as you point out
Mike, it is a crucial issue.

Also see new thread at WUWT :

Dec 7, 2014 at 3:39 AM | Unregistered CommenterAnything is possible

Radical Rodent and Anything is Possible:

that is a classic anecdote of a high school student demonstrating problems with temp. correlations to tree ring growth, but it did not come from UEA -- that Tom is Tom Wigley, I believe, who was at NCAR (National Center for Atmospheric Research) in Boulder, Colorado when his son did that work and when Wigley wrote about it to climate science colleagues.

[Wigley was previously Director of the CRU at UEA until 1993, so you're not too far off, but if I understand correctly he was writing of an experiment done in Boulder, CO]

Dec 7, 2014 at 6:42 AM | Registered CommenterSkiphil

Thank you for the comment about boreholes. If I am recalling correctly, Steve Mc mentioned awhile ago that based upon his review of borehole data he didn't have too much regard for boreholes as temperature proxies, but I can't say.

Dec 7, 2014 at 6:44 AM | Registered CommenterSkiphil

As I understand it, Manns erroneous methodology would have rejected this particular series.

Dec 7, 2014 at 12:52 PM | Unregistered CommenterRobinson

All the ancient trees that died in the effort--what of them?
Dec 7, 2014 at 3:25 AM | Unregistered CommenterLarry Sheldon
Best laugh I've had all day.

Larry, for me at least, you win the internetz for Dec 7.

Please stick around here.

Dec 7, 2014 at 1:24 PM | Registered Commenterjohanna

OT but do you know what happened to the CET anyway? Around 10 years ago I checked that the Armagh observatory was regarded as the best temperature record in the UK and it showed nothing in the way of significant changes - not only that but there were a few papers that documented a correlation with sunspots. When I noted that result I double-checked with the CET and there was nothing unusual happening there either. Yet now there is a plateau that somehow I didn't manage to notice before.

Dec 8, 2014 at 10:38 AM | Unregistered CommenterJamesG

JamesG- how very interesting.
Maybe the "waybackmachine"
might have a record of what you saw?

Dec 8, 2014 at 12:57 PM | Unregistered CommenterBitter&Twisted

It has been obvious from day1 that a tree ring would never be a proxy for temp
One has to take all possible diverse proxies and derive FUNCTIONS (combinations) out of them that might be a proxy.

The written record of humanity in Europe and China could be calibrating functions as people did write down whether it was
a "terrible" winter prior to the Battle of Hastings etc.

This is a "Big Data" exercise. Probably better left to superior digital intelligence, further down the road.

Our task is/should be to start producing better, raw data, online.
Not to come with some Pine Cone and shout you have found the Holy Grail and proved Gerbil Worming..soo Goebbels.

Dec 8, 2014 at 2:12 PM | Unregistered Commenterptw


cant say I noticed a plateau in CET but I suppose it depends how you calculate a running average. Here is an article I wrote last year in which I graphed CET in various ways.

I met David Parker last year at the Met Office who created the record to 1772. They recently swapped some of the stations used as they were running a little warm.

I would suspect the hump we see in Hadley CET 1772 (and the resultant high temperatures?) is exaggerated by a few tenths of a degree by this factor.


Dec 8, 2014 at 5:53 PM | Unregistered Commentertonyb

Picture perfect correlation between this tree and the 1970's global cooling scare, demonstrating how robust tree ring proxies are.

Jan 9, 2015 at 12:03 AM | Unregistered CommenterMorgan Wright

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