One day walking from my home to work and crossing a footbridge over the River Yare into the inner sanctum of UEA, I was appalled to see a beautiful line of crack willows, the haunt of many a kingfisher, was being felled. These trees had graced the river bank for around a century (estate records exist of their planting). Apparently increased river flows were undermining the tree roots and the trees were now considered a danger to canoeists, fishermen and passing pedestrians alike. I spoke to the chief fellah (feller?) and asked if he could keep for me a slice through a tree trunk that showed the least amount of damage and was as close to the ground as possible. Crack willows are well named since they develop deep fissures, and I wanted the least damaged specimen. I planned to get one side of the slice polished and its tree rings counted and annotated. I thought it would fit well at the entrance foyer of the School of Environmental Sciences, especially if we could identify and highlight the years when UEA was founded and ENV moved into its current building, as well as dates of lesser importance like the beginning and end of WW2. I already had a photograph of the tree-lined river bank to accompany the tree slice that would inform visitors of the former beauty of the river banks.

A few days later, whilst crossing the footbridge again, I was presented with a tree slice around 10cm thick and 60 cm across, within which the tree rings were prominent and rather thicker than I had expected. I had it polished and set about counting down the tree rings to discover how many there were and the location of particular years.  

While I was tree-ring counting, Keith Briffa of CRU (= Professor Tree Ring) came into my office. His comments, as far as I remember them were:

1) Pity the tree hadn’t been an oak, because that would have been ‘much more useful’ and,

2) (Looking at my pencil marks where I had dated individual tree rings), ‘You appear to have missed some’ (I hadn’t).

He showed little interest in what the tree slice was intended for (perhaps if it had been from an oak?)

Tree rings as temperature proxies?

Part of the reason for my interest in tree rings was that I had always been sceptical that the width or density of tree rings could record varying temperatures and particularly reflect some average global temperature. I therefore questioned if they could act as reliable temperature proxies for past times (a view I still hold). I did learn over the years that it wasn’t as simple as I had originally thought, that the data came from locations that were marginal for tree growth and where the variable most likely to be controlling growth was temperature and not water supply or sunshine amounts. But still a question remained for me: could those special locations be representative for global climate fluctuations? Also, surely the global variations would affect those special locations (otherwise why bother?), potentially making trees growing there more or less sensitive over time to climate variables other than temperature. The more I examined the arcane practices of dendroclimatology, the more it seemed to be voodoo science. But I never could express this to its practitioners in CRU, because to do so would strain relationships, perhaps beyond repair (and I still had to work with them).  So I kept my own counsel.

Climategate changed things. Strain increased between CRU and myself, but with discussions raging everywhere in and outside the university about ‘hiding the decline’ I felt less constrained to express my doubts and thoughts about tree rings (and other proxies). I also began to think outside the box about how to employ tree ring variability to unravel the various and variable controls upon the thickness of those tree rings. I came up with two strategies that might show promise.  

The first strategy was to pick upon a single widely grown tree species (probably a conifer) and compare its reaction (by tree rings) to varying climatic variables across the U.K. from high altitudes to low, from the wetter west to the drier east, and also taking into consideration changing levels of light intensity sunshine and or cloudiness. I was reasonably certain that this would already have been done, but was assured that it hadn’t been, or not with the rigour that I was proposing.

For my second strategy, I recalled Keith’s reaction to my crack willow slice. Why would he prefer an oak? Now, I think it was because oak tree rings are very narrow and, for a 60cm wide slice, there would be a longer history to unravel. But when I initially was thinking about it (probably wrongly) I wondered if it might be due to the obvious fact that living alongside a permanently flowing river, the willows were never afflicted by a shortage of water, thus this variable could be excluded as influencing annual tree ring width. Thinking more widely, I thought that different types of tree might react to different climatic variables to different extents. Consequently, sampling many different tree species from a single locality might reveal these different influences (not just temperature) and thus show their variability over time with, say dry years, having a greater effect in some species than in others, whereas a different suite of species might be more affected by late frosts, and so on. I proposed that this sort of study might be suitable for an undergraduate thesis, sampling from different trees within the UEA campus. However I could never conjure up enough interest within CRU to supervise such a  project, nor with any undergraduate. So it remains a future project for someone. I was surprised at the apathy from CRU, because with a relatively small investment of their time they might have gained better understanding of what controlled a tree’s response to different climatic variables and so potentially improved their proxy records. But hey-ho.

The decline controversy

After Climategate 2, I became embroiled in a blog war over whether or not I should heap further calumny upon my former colleagues within CRU. One of the main bones of contention concerned Phil Jones’ email where he wrote:

“I’ve just completed Mike’s Nature trick of adding in the real temperatures to each series for the last 20 years (i.e. from 1981 onwards) and from 1961 for Keith’s to hide the decline.”

The words ‘trick’, ‘hide’ and ‘decline’ caused sceptics worldwide to go apesh!t. Gallons of printer’s ink were spilled trying to manufacture nefarious explanations for these words, especially concluding that ‘the Team’ were trying to disguise the fact that global temperatures had fallen. Nothing could be further from reality. Phil Jones, Keith Briffa, Tim Osbourne and others complained bitterly that the Climategate emails were being interpreted out-of-context and that Phil Jones’ ‘hide the decline’ email was a perfect case in point. I agreed with them on this one point.

In the email the word  ‘series’ referred to three different attempts to reconstruct average temperatures of the past using proxies, mostly from tree rings.

‘Mike’s Nature trick’ was to add the 19th and 20th century instrumental temperature record to the end of Mike’s proxy record, so emphasising (exaggerating?) the ‘unprecedented’ global warming. Jones was employing the same device (or ‘trick’) on a diagram he was constructing that used the three different proxy records (or series), including one from Briffa that employed a new technique using summer wood density (rather than tree ring widths) as the proxy. When applied to past centuries this new technique gave results that tracked those using tree ring thicknesses and so was accepted as a valid indicator of past temperatures. That is up to around 1960 when the Briffa technique goes amok. Temperatures determined by thermometers (and some averaging chicanery) showed a steep rise post 1960, but the Briffa proxy temperature curve displayed an equally steep decline. So the ‘decline’ in Phil’s infamous email did not refer to instrumentally determined temperatures, but to temperatures determined from summer wood densities which were considered spurious. Jones resolved his problem of constructing a diagram showing what he wanted to show by omitting the Briffa curve after 1940, so ‘hiding the decline’.

After the Climategate email release the CRU part of ‘the Team’ were up in arms, loudly protesting their innocence. They argued, with some justification, that they were only trying to tidy up an already overly complicated diagram by removing part of a proxy curve that was obviously wrong. I understood that Keith Briffa strenuously objected when it was suggested that his entire proxy curve be removed from the diagram and still was unhappy when the last part of his curve was obliterated. He wanted his work acknowledged and used.

At the time I totally agreed with CRU that criticisms that they were hiding a fall in average global temperatures were incorrect. They were instead hiding what they considered spurious data where tree-ring derived temperatures did not replicate their interpreted unprecedented steep rise in thermometer-determined temperatures. This was bad enough because it also hid the possibility that the tree-ring proxy method could have ‘gone rogue’ at other times and so the various reconstructed temperature curves may have omitted previous warm periods (like the Medieval Warm Period).  

In the intervening years my judgement upon this matter has changed. Removal of the most recent parts of the proxy curves were indeed hiding an apparent decline in temperatures because it was a reconstructed temperature curve that was being hidden, not a curve displaying tree-ring widths or densities. The fact that they could argue that only spurious data was being removed was not pertinent. They could not demonstrate that earlier parts of their proxy-determined temperature plots were not free of the same ‘errors’.  

I also found Keith Briffa’s reluctance to use the crack willow and give support for a proposal to examine different tree species on the UEA campus difficult to defend. The reason why tree-ring wood densities are seemingly controlled by temperature at some times but not at others is still unknown. In keeping with the mantra that recent high temperatures have been caused by human release of carbon dioxide ‘pollution’ the recent deviant behaviour of tree-ring densities has also been ascribed to other human changes – global dimming, pollution either acting directly or indirectly as when the protective cover of stratospheric ozone is destroyed. But, as far as I know, this is all conjecture with no proof. What cannot be admitted is the possibility that whatever the cause of the anomalous tree-ring density and temperature relationship, it could have acted before the period when past temperatures were available from thermometers. That would open up an entire can of worms that dendroclimatologists seemingly could not face.

The fate of the tree slice

I suppose many of you are eager to learn what happened to the tree slice. I am sorry but I can’t tell you, not because I’m sworn to secrecy but because I just don’t know. I left UEA without it being installed, and last I saw, it was in the office of ENV’s Head of School, gathering dust. I am informed that it is not on display anywhere.

Dendroclimatology was a genuine attempt to extend our knowledge of past climates but attracted ‘bad vibes’ for the School that I doubt have entirely gone away. Perhaps a display of tree rings would have stimulated too many bad memories. Most likely the tree slice, still with my pencil marks upon it, resides in a storeroom somewhere, unloved, somewhat like the fate of the biblical artifact in Raiders of the Lost Ark.


  1. When the Climategate apologists stepped forward to play down the use of the word ‘trick’, claiming it was being used in the sense of a mathematician’s technique, I was somewhat surprised that the mathematicians of the world didn’t all jump to their feet in righteous indignation. To a mathematician, a trick is the application of a well-proven procedure that facilitates an otherwise difficult or seemingly impossible calculation. What the climate scientists were doing was a million miles away from that. Indeed, they weren’t even engaging in any mathematical calculations – just the presentation of datasets in a graphical form. It is quite obvious that the word ‘trick’ was being used here in the magician’s sense of misdirection, as an attempt to hide something that would otherwise spoil the illusion.

    I am disappointed that those involved should have stooped to attempting such a feeble defence but I am even more disappointed that so many people were satisfied by it. As Alan’s excellent article points out, the hiding of the decline may well have been a perfectly innocent presentational technique used to ensure that the temperature history was readily apparent to the audience, but it also had the effect of conveniently hiding from them the true status of dendroclimatology as a science and, hence, misrepresented the reliability of that history.

    Liked by 1 person

  2. Academics are incredibly careless with the stuff they’re given. I’m afraid your split willow probably went the way of Phil’s floppy discs. I once found a 19th century African explorer’s photo album in a dustbin behind the Museum of Wales, and a friend researching musical instruments was given a couple of tea chests full of stuff left by Sir Charles Wheatstone (of the bridge of that name) to the Science Museum, containing, among a load of aborted inventions, a baroque flute which my friend sold at Sotheby’s for a tidy sum.

    Liked by 1 person

  3. Two things I know about Wheatstone:

    1) He didn’t invent the Wheatstone Bridge

    2) He did invent the concertina

    It’s a shame that the latter wasn’t in that box of aborted inventions.

    Liked by 2 people


    He did invent the concertina. It’s a shame that the latter wasn’t in that box of aborted inventions.

    You’re probably thinking of the Anglo-German concertina, which is an instrument played by circus clowns and Jolly Jack Tars. Wheatstone’s invention was the English concertina, an instrument for gentlemen.
    I used to play in an English concertina band. We thought we were the only one in the world, but there’s another in a school for the blind in Kenya. We were quite big in folk clubs at one time, and even did a tour of Belgium, which was aborted when the IRA blew up the stage we were due to play on.

    Liked by 3 people

  5. I do most strenuously object to my beautiful crack willow tree, that gave its all to science, being compared with a picture of Tony Thomas’s wanton tree (in a suggested related article).

    [Sadly we have no control of the algorithm that purports to show related articles. Another great post, though, Alan. — Scepticus]

    Liked by 2 people

  6. Geoff,

    No, actually I was thinking of the English concertina. As for being a gentleman’s instrument, I am reminded of the quip, usually misattributed to Oscar Wilde, that ‘a gentleman is someone who can play the accordion but chooses not to.’ It is normal to substitute one’s own pet dislike in this quote, e.g. bagpipes, cornet, etc. I nominate the English concertina for no better reason than that it pleases me to do so.

    Liked by 1 person

  7. To illustrate the subjective nature of much of dendrochronology, let alone dendroclimatology, try counting the number of annual tree rings in the slice photograph used to introduce my article. Use the entire slice. You will find that what you take as a single yearly increment in one part of the slice may seem to show additional layers in other parts. How about layers in the youngest (= outermost) parts? Then as a dendroclimatologist you will be interested in the thickness of the different layers. But hold on, for some years the thickness varies as you trace a layer around the slice. Nor do the thickenings and thinnings occur in the same segment in the different year increments. So what do you measure? I never could get a consistent methodology from CRU. I really did agonise over the procedures used for strip bark trees, which exhibit extreme lateral variation, but upon which much of the original hockey stick diagram was based.

    I hasten to add that my agonising did not actually concern trees. At the time I was doing work on calcium sulphate evaporite deposits that displayed thin (possibly annual) layers, like varves. As salinities increased in the evaporite basin, the varves began to thicken, but also became highly contorted and of irregular thickness (especially just before evaporite precipitation changed from calcium sulphate to sodium chloride). Previous researchers had reported and quantified the thickening of the irregular layers, but we couldn’t discover how this was done. Measurements made by different people in our study were different. This problem was essentially the same as measuring the thickness of irregular annual increments in strip bark trees. We never came up with a procedure that everyone agreed was consistent and repeatable. I strongly believe measurements on strip bark trees was similar and was fudged.

    Liked by 1 person

  8. ALAN
    If you think your stripped willow cross section is a bit wonky, have you seen the photo of a cross section of a strip bark pine that Steve McIntyre once published? It’s kind of amoeba shaped, with excrescences. The original researchers apparently didn’t cut down trees, but drilled boreholes where the fancy took them.


  9. Geoff,

    I’m not actually sure what species of tree is featured here.

    As for the Wheatstone debate, I hasten to add that I have nothing against English concertina players. I just don’t like the sound of an English concertina, and if I ever had the opportunity to hear one played, I suspect I’d dislike it even more.


  10. Geoff.
    You wrote: … “cross section of a strip bark pine that Steve McIntyre once published? It’s kind of amoeba shaped, with excrescences”

    This is exactly the point that I was trying to make. The problem is just about discernible in the tree slice used to illustrate the article, but in strip bark trees the problem is extreme. Much of the time the strip bark trees don’t grow over much of their trunks, so that a single bore would not provide a continuous record. As I wrote – I never established the methodology used in getting the records. Even if you were allowed to obtain a slice through the tree trunk (so killing the tree) I doubt that you could devise a methodology that would yield reproducible and meaningful results from strip bark trees.

    Surprisingly, my crack willow slice had very uniform growth layering. Traced around the slice, annual layers did vary some, but they all changed rather uniformly.

    In the illustrated slice, annual growth layers reveal internal layering, some of which die out when traced around the growth ring. Do these correspond to storm events that affected one side of the tree more than the other? So much to see, so much to interpret and learn from. I honestly never heard these problems discussed by CRUites.

    Liked by 1 person

  11. I thought I spotted a logical problem with the whole tree ring business. I once raised it at Climate Audit but I was politely ignored.

    I understand that, in order to determine whether temperatures have varied in past centuries, you have to take samples at the tree line, i.e. the altitude which marks the limit where that species will grow, in order to eliminate other confounding factors like precipitation and shade. But if the temperature changes, so will the tree line. If it was warmer in the past, then the tree line would have been higher, and the trees you’re sampling now would have been some way below it, other saplings which might have sprouted up in past centuries having died off in the meantime. But if it was colder in the past, then today’s trees (at the limit of their growing capacity because they’re at the tree line) would have never got going in the first place. In other words, the reasoning behind the whole project is basd on a circular argument.

    Liked by 1 person

  12. Again Geoff. Great minds think alike. I wrote
    “ But still a question remained for me: could those special locations be representative for global climate fluctuations? Also, surely the global variations would affect those special locations (otherwise why bother?), potentially making trees growing there more or less sensitive over time to climate variables other than temperature.”

    The “special locations” correspond to your “tree line” and climate changes would alter their “special” character, changing their ability to provide good temperature data.

    Actually I think a tree line affects the viability of saplings to survive. If the climate cools, existing trees, now beyond the tree line, still continue to grow but saplings die. In contrast, if the climate ameliorates, new saplings germinate in the newly habitable area, but older trees within the area formerly growing near the old tree line may now respond to other climatic variables and not just temperature. In other words, those areas would no longer be special and provide the information needed.

    Liked by 1 person

  13. Ecologist Jim Bouldin, once he was bounced off the Real Climate blog, posted a fascinating series of posts on his own blog about the problems with tree rings as treemometers. One of his points was that a narrow ring could mean that the temperature was low that growing season or that it was too high. And without other evidence, how could you even guess? It’s like with spaeliotherms: you have to know whether they are downstream or upstream from a glacier before you know how to interpret the annual growth with relation to temperature. It just seems like a waste of effort


  14. Mann et al 2008 performed temperature reconstructions with and without tree-rings. You can see the different curves in the Fig S7 of the SI here The limitations of dendrochronology and divergence problem are both discussed in the main paper here:

    (BTW, Figure S8 in the SI shows the effect on the reconstruction of removing a handful of proxies with potential data quality issues, including the notorious Tiljander lake sediments)


  15. Phil, the hockeystick reconstruction without the four Tiljander series included bristlecones, did it not? See contemporary and very detailed analysis at Climate Audit.

    Liked by 1 person

  16. Sorry, I have read a lot of McIntyre’s output on this and simply do not find him credible. The genuine flaws he detects turn out to have negligible impact and the ones that would cause a significant alteration turn out not to be correct. Wahl and Amman (2007) repeated the hockey stick study with and without the ‘controversial’ strip bark bristlecones and found excluding them made no significant difference, and that excluding the data reduced the validation skill of the reconstruction, implying that it contained valid climatological information.

    “Results for the exclusion of the bristlecone/foxtail pine series developed according to scenario 3 are shown by the green curve in Figure 2. The exclusion of these proxy records generally results in slightly higher reconstructed temperatures than those derived from inclusion of all the proxy data series, with the greatest differences (averaging ∼ + 0.10◦) over the period 1425–1510. The highest values before the 20th century in this scenario occur in the early 15th century, peaking at 0.17◦ in relation to the 1902–1980 mean, which are nevertheless far below the +0.40–0.80◦ values reported for scenario 1. The verification RE scores for this scenario (Table 2) are only slightly above the zero value that indicates the threshold of skill in the independent verification period, and the verification mean reconstructions are correspondingly poor. The poorer performance of Scenario 3 in relation to Scenario 2, which cannot be attributed to calibration overfitting because the number of proxy regressors is reduced rather than augmented, suggests that bristlecone/foxtail pine records do possess meaningful climate information at the level of the dominant eigenvector patterns of the global instrumental surface temperature grid. This phenomenon is an interesting result in itself, which is not fully addressed by examination of the local/regional relationship between the proxy ring widths and surface temperatures (noted in Section 1.1) and which suggests that the “all proxy” scenarios reported in Figure 2 yield a more meaningful comparison to the original MBH results than when the bristlecone/foxtail pine records are excluded. Even in the absence of this argument, the scenario 3 reconstructions in the 15th century do not exhibit large enough excursions in the positive direction (in relation to the 20th century instrumental record) to yield a double-bladed hockey stick result that diminishes the uniqueness of the late 20th century departure from long-term trends. ”

    Fig 2 is here,

    The green line is the reconstruction without the allegedly problematic strip bark samples.

    It is the case that the 2006 NAS panel recommended that strip bark samples not be included in temperature reconstructions, however in 2009, Salzer et al revisited the site of the Bristlecones and published these conclusions:-

    “At 3 sites in western North America close to the upper-elevation limit of tree growth, Great Basin bristlecone pine (Pinus longaeva) showed radial growth in the second half of the 20th century that was greater than any time in the last 3,700 years. We have shown several new lines of evidence that suggest that at the upper forest border bristlecone pine ring widths have responded to temperature in the past and continue to do so. (i) The unique 20th-century increase in ring width is specific to the upper forest border and is not associated with a particular elevation. The link to upper treeline rather than to a specific elevation is not consistent with the WUE hypothesis of indirect fertilization by CO2 or fertilization by nitrogen deposition. (ii) The strong modern trend in growth observed at the upper forest border is not the product of any preprocessing or standardization of the data—there was none. (iii) The modern trend is not related to the difference between strip-bark and whole-bark growth forms.”

    Recent unprecedented tree-ring growth in bristlecone pine at the highest elevations and possible causes.
    Matthew W. Salzer, Malcolm K. Hughes, Andrew G. Bunn, and Kurt F. Kipfmueller


  17. “Wahl and Amman (2007) repeated the hockey stick study with and without the ‘controversial’ strip bark bristlecones and found excluding them made no significant difference, and that excluding the data reduced the validation skill of the reconstruction, implying that it contained valid climatological information.”

    Doesn’t this raise even the teeny-weeniest bit of doubt in your mind Phil. That records based upon plants that do not grow radially or uniformly around their trunks, which have large areas of their trunks lacking living cambium (which lays down woody tissue) can be used with impunity to obtain records of past temperatures? How can you even obtain a consistent record at all? and that’s before you even begin to consider whether the width of the tree rings are responding to temperature, or to something else like moisture, CO2, or UV levels, or most likely a fluctuating amalgam of these controls.

    Doesn’t the fact that inclusion or exclusion of this type of highly suspect data has little effect worry you in the slightest? Doesn’t it suggest that the manner the data (= any data) is processed will produce the desired result – a hockey stick and unprecedented recent warming, oh sorry heating? Whal and Amman’s conclusions, for me, merely raise questions about data manipulation.

    And it’s not just bristlepines is it? Upside-down lake deposits anyone? I would be mightily embarrassed, nay ashamed, if I had been found to have been so careless. And to compound the “mistake” by running the analysis without the upside-down lake sediment records, or with the sediments right way up, and announcing that it made no discernible impact, just adds more rubbish onto the pile.

    Liked by 2 people

  18. Phil, if you have read Climate Audit, you must be aware that Salzer et al was discussed at length with less than favourable conclusions. For my part I was instantly suspicious that the authors had set out searching for a particular answer, and I don’t think the discussion changed my view.

    As for McIntyre having negligible impact, next you’ll be telling me that Gergis et al 2012 coincidentally noticed they were using plain series rather than detrended series at the precise time that Climate Audit noticed it. Without Climate Audit, and I don’t mean just Steve McIntyre alone, I mean him plus the other major contributors there, that paper would now be carved in stone instead of on the scrapheap.

    Liked by 3 people

  19. Salzer et al found this:-

    “The lack of a substantial difference in ring width between our strip-bark and whole-bark groups in the modern period appears to contradict the finding of Graybill and Idso (13) for the same species in the same mountain range. In fact, when their raw ring widths are plotted in the same manner as our Fig. 3, there is little difference between their strip-bark and whole-bark groups in the modern period (Fig. S4A). The apparent divergence of their strip- and whole-bark chronologies from the mid-19th century to the late-20th century is the result of the standardization scheme they used (Fig. S4B). When compared in an appropriate manner, without artifacts introduced by standardization, recent growth rates of strip-bark and whole-bark trees from the same environment are very similar. In light of these results, the suggestion that strip-bark pines should be avoided during analysis of the last 150 years (27) should be reevaluated.”

    I can only find one discussion of the paper at CA, here McIntyre writes

    “We observed that there were a variety of issues surrounding whether bristlecone chronologies were unique antennae for world climate. In addition to being stressed by cold, Sheep Mountain bristlecones are in an extremely arid environment and subject to more than one stress.

    These issues are not canvassed in Salzer et al; instead, they argue that the chronologies are correlated to modeled high-altitude temperature- something that will be discussed on another day.”

    Firstly, Salzer et al does discuss precipitation, and main conclusions of the paper are temperature-based, so what the flip is he on about? Secondly if he did go onto discuss the issues ‘on another day’, I can find no record of it at Climate Audit and it would have been the work of a moment to update that post with a link. Thirdly, his Figure 5 seems to me actually to provide support for Salzer’s conclusion that ‘recent growth rates of strip-bark and whole-bark trees from the same environment are very similar’.

    As for Tiljander, it was not used ‘upside down’, the calibration process indicated the sign of the correlation. The choice was to use it as the algorithm indicated or not use it at all. In the end they did both. The authors were well aware of the possible contamination:

    “. In addition to checking whether or not potential problems specific to tree-ring data have any significant impact on our reconstructions in earlier centuries (see Fig. S7), we also examined whether or not potential problems noted for several records (see Dataset S1 for details) might compromise the reconstructions. These records include the four Tijander et al. (12) series used (see Fig. S9) for which the original authors note that human effects over the past few centuries unrelated to climate might impact records (the original paper states ‘‘Natural variability in the sediment record was disrupted by increased human impact in the catchment area at A.D. 1720.’’ and later, ‘‘In the case of Lake Korttajarvi it is a demanding task to calibrate the physical varve data we have collected against meteorological data, because human impacts have distorted the natural signal to varying extents’’). These issues are particularly significant because there are few proxy records, particularly in the temperature-screened dataset (see Fig. S9), available back through the 9th century. The Tijander et al. series constitute 4 of the 15 available Northern Hemisphere records before that point. In addition there are three other records in our database with potential data quality problems, as noted in the database notes: Benson et al. (13) (Mono Lake): ‘‘Data after 1940 no good— water exported to CA;’’ Isdale (14) (fluorescence): ‘‘anthropogenic influence after 1870;’’ and McCulloch (15) (Ba/Ca): ‘‘anthropogenic influence after 1870’’. We therefore performed additional analyses as in Fig. S7, but instead compared the reconstructions both with and without the above seven potentially problematic series, as shown in Fig. S8.”

    So they did the reconstruction with and without the proxies with potential quality issues. What more do you want? Here is plot without tree-rings and without Tiljander etc (The plot ends in 2000, so add on another 0.2C or so of modern global warming)

    Click to access NHcps_no7_v_orig_Nov2009.pdf

    As for Gergis et al, 2012, it is by no means on the scrap heap. As you note, it was not McIntyre who commented on the detrending issue but ‘Jean S’, and Gergis claims they had detected it themselves two days earlier. Who cares? The paper was reworked and republished in 2016, the conclusions virtually unchanged. The PAGES 2K consortium published a virtually identical Australasian reconstruction. So I am struggling to see that the impact of a comment on McIntyre’s website was anything other than negligible.

    It is difficult to debate somebody whose starting point assumes bad faith and that is a good description of Mr McIntyre. There’s a lot that should raise eyebrows. He’s engaged in behaviour that would result in prompt dismissal were he working as a professional scientist. In the period after the MBH studies were published he took to Usenet under the pseudonym ‘Nigel Persaud’ and wrote malicious and defamatory comments about the work of Michael Mann and other climate scientists while boosting his own efforts with Ross McKitrick. He is not averse to a bit of quote mining. One of his frequent complaints is that he cannot obtain data from genuine scientists, however even when the data is sent he has been known to hide the fact:

    “McIntyre: A few days ago, I became aware that the long-sought Yamal measurement data url had materialized at Briffa’s website – after many years of effort on my part and nearly 10 years after its original use in Briffa (2000).

    Hantemirov: Steve has an amnesia. I had sent him these data at February 2, 2004 on his demand.”

    McIntyre made the claim that the Mann et al algorithm would produce Hockey Sticks out of randomised ‘red noise’. As it turned out they were using a highly unrealistically auto-correlated input and data-mining the output. He has allowed his website to be used as a vehicle for vexatious FOI requests. His blog science has horrified at least one professional dendrochronologist:

    “Steve, I’m horrified by your slipshod work. You did not define what you compare, what dataset used in each case, how data were processed, and what was the reason for that, what limitation there are, what kind of additional information you need to know. Why didn’t you ask me for all the details? ”

    And so on, and so forth. Seems clear to me that to take anything he writes at face value is something of a category error. I am genuinely bemused that anyone takes him seriously. (scroll down).


  20. Phil, the detrended vs. plain series issue should not have mattered. Gergis et al made it matter. They could have acknowledged Climate Audit and the mistake and reported the results as obtained by the methods they claimed to have used. That only 6-9 series (seems to depend who you ask) of the 27 passed the screening using the reported method as opposed to the actual method meant the “network” was then probably a bit underwhelming. Did they form a hockeystick? We’ll never know.

    I do not believe for one moment that they spotted the error independently. That wouldn’t matter unless they were to claim that they did so, which they did. (The time stamps on the emails that McIntyre obtained under FOI support his version.)

    Gergis then referred to a “typo” being the cause of all this trouble. But a typo has never resulted in a paper being retracted. If it was a typo then a single word change in the MS, which had still not been printed, was all that was required.

    That the final network using detrended series closely resembled the original, despite two thirds not passing the screening initially, is a source of wonder. To some it looks like confirmation of the original result. To others it looks like the result was predetermined. The new screening (I’ve just been back to Climate Audit to read about it) was not “plain series vs grid cell temperature” as the original. Instead it was “detrended series at -1, 0 or +1 lag, vs grid cell plus all adjacent grid cell temperatures.” (I even found a comment of mine saying that the grid cell temperatures probably had a high degree of autocorrelation, so the issue of picking multiple targets to aim at might not have been that serious.) In any case there is a well-known procedure called the Bonferroni correction that in its simplest form just reduces your significance threshold in proportion to the number of tests. It was not used. At the time commenters ridiculed the possibility that tree rings might determine future temperatures (i.e. with the -1 lag), although to my eye it was more a problem that the original series were not dated using the same method.

    McIntyre had always, always, banged on about screening. It was obvious by an elementary study of those early tries that using an instrumental target and a plain series just mined for hockeysticks. Not rocket science. Hockeystick science. Detrending was a good answer to part of the problem (note: not the whole problem). But they just had to ruin things by all this jiggery-pokery.

    I am absolutely sure that the hockey team were watching every post that appeared at Climate Audit with a high degree of trepidation. They knew that Steve and some of the others there were smarter than them. If only they had engaged there and tried to get to the right answer, in a “disinterested search for truth,” rather than belittle and dismiss his efforts in public while dashing around like disturbed ants in private trying to sticky tape flawed results back together. Steve made mistakes. But you cannot hold a blogger to the standards of international teams of scientists whose output is supposed to be informing policy, policy that even now is changing our way of life in more extreme ways than climate change will. Hockeysticks have a lot to answer for.

    In any case, after what was it, three revisions, four years, twenty reviews (I can’t remember the specifics), out came the new version, closely resembling the old version. (I feel a song by The Who coming on.)

    Liked by 1 person

  21. I’m amazed people are still going on about this. There have been so many millenial temperature reconstructions that the basic picture is now pretty clear.

    Ultimately, there are those who are trying to use innovative methods to understand our millenial temperature history, and there are others who are spending their time trying to find any reason to criticise the work of the first group. McIntyre is not in the first group.


  22. ATTP,

    You should try not to be so amazed all the time. If I had set out to develop a discipline that was susceptible to experimenter’s bias I could not do a better job than paleoclimatology. Even if it turns out to be the only scientific endeavour in history to be immune from such, you still could not blame those who are not fully involved for being wary of the possibility. A lasting preoccupation with the allegations made in the early days of hockey stick generation is only to be expected, because for some, with experimenter’s bias in the back of their mind, there is only so much reassurance that can be taken from the argument that ‘a thousand flies cannot be wrong’.

    Liked by 2 people

  23. One disagrees often with what Steve McIntyre, that noble and disinterested seeker after the truth has to say. But he sometimes talks sense:

    “While there is much to criticize in the handling of this data by the authors and the journals, the results do not in any way show that “AGW is a fraud” nor that this particular study was a “fraud”.

    There are many serious scientists who are honestly concerned about AGW and your commentary here is unfair to them.

    In retrospect, the “hockey stick” studies that I’ve criticized have been used by climate scientists, journals and IPCC to promote concern, but the most important outstanding scientific issue appears to me to be the amount of “water cycle” feedback, including clouds as well as water vapor. This controls the “climate sensitivity” to increased CO2.

    In my opinion, scientific journals reporting on climate and IPCC would serve the interested public far better if they focused on articulating these issues to the scientific public at a professional level than by repeatedly recycling and promoting some highly questionable proxy studies that deal with an issue that interests me, but which is somewhat tangential to the large policy issues.”

    – Steve McIntyre

    Comment left at The Spectator taking Melanie Phillips to task for her over the top accusations after the Yamal nontroversy.

    Hockey Stick – ‘Somewhat tangential’ to policy. True in 2009, even more so now.


  24. John,

    You should try not to be so amazed all the time.

    Using the term “amazed” was me trying to be polite.

    [You didn’t succeed. Try answering John’s substantive points. These kind of non-answers will be put in spam in future. — mod]

    Liked by 1 person

  25. ATTP,

    >“Using the term ‘amazed’ was me trying to be polite.”

    And yet it isn’t being in the least bit polite of you to express amazement that anyone should think something important, is it? In fact, it is designed to cause maximum offence, since it serves to belittle and deride. You play the gentleman pugilist surrounded by thugs but, in truth, you’re just street-fighting like the rest of us.

    It would, I think, be helpful to discuss the potential for experimenter bias in a field where data selection and statistical analysis play such a huge role, and where the main objective appears to be the confirmation of a belief already underpinned by so much political and intellectual investment. Statistics is a notoriously problematic area for the researcher to come to terms with, and abuse, both deliberate and unintentional, is not uncommon, as is suggested by the opening lines of a guide written by Alex Reinhart, assistant teaching professor of statistics and data science at Carnegie Mellon University:

    “If you’re a practicing scientist, you probably use statistics to analyze your data. From basic t tests and standard error calculations to Cox proportional hazards models and propensity score matching, we rely on statistics to give answers to scientific problems.

    This is unfortunate, because statistical errors are rife.”

    For example, what may be of particular relevance here is the problem of pseudo-replication. Then there is the problem introduced by having too much freedom to choose statistical techniques:

    “The most concerning consequence of this statistical freedom is that researchers may choose the statistical analysis most favorable to them, arbitrarily producing statistically significant results by playing with the data until something emerges. Simulation suggests that false positive rates can jump to over 50% for a given dataset just by letting researchers try different statistical analyses until one works.”

    To be clear, I am not claiming here that such practices have actually featured in paleoclimatology, but I do think there is sufficient legitimate concern to justify outsiders asking questions. You should not be amazed by this and you should not look upon their persistence dimly.

    Liked by 2 people

  26. Phil,

    >”Hockey Stick – ‘Somewhat tangential’ to policy. True in 2009, even more so now.”

    I’m not sure I can agree entirely with that statement. It is certainly the case that the hockey stick is now somewhat tangential to policy. Even if a new temperature reconstruction were to emerge tomorrow that showed a Medieval Warm Period that stuck out like the proverbial pig in a snake, that wouldn’t change a thing, since policy is now well and truly established. However, when the hockey stick first emerged, it wasn’t so long beforehand that the IPPC had been saying things like:

    “A global warming of larger size has almost certainly occurred at least once since the end of the last glaciation without any appreciable increase in greenhouse gasses. Because we do not understand the reasons for these past warming events, it is not yet possible to attribute a specific proportion of the recent, smaller warming to an increase of greenhouse gasses.”

    The hockey stick changed all of that by appearing to remove the need for an explanation for ‘these warming events’. I think this was hugely important – not tangential at all. The IPCC certainly made enough fuss about it at the launch of AR3. Even as late as 2007, it was still important to the IPCC to lay claim to unprecedented warming – evidence its AR4 Summary for Policymakers:

    “Average Northern Hemisphere temperatures during the second half of the 20th century were very likely higher than during any other 50-year period in the last 500 years and likely the highest in at least the past 1300 years.”

    You don’t get to say that sort of thing without a hockey stick.

    Liked by 3 people

  27. MIAB,

    >”You treat climate enforcers as normal human beings at your peril.”

    Maybe, but what is normal anyway? In fact, I think you will find that most ‘climate enforcers’ are just normal people. And, to be fair, I don’t think either ATTP or Phil can be called dim. That said, what with ATTP being ‘amazed’ and Phil being ‘generally bemused’, it doesn’t look like they would be as prepared to say the same about us.


  28. Perhaps if you speculate what fuel Phil Clarke or ATTP will be using to heat their homes in 2035 we might have an answer. They will have moved to the tropics, following their principles


  29. ATTP,

    >”FWIW, I don’t think the issues here has anything to do with people being dim”

    Well I’m glad to see that we are very much in agreement on that point.

    >”and, just to be clear, there’s no hidden subtext here”

    Then perhaps it was inappropriate for you to have alluded to one by saying “Using the term ‘amazed’ was me trying to be polite.” I could continue to probe by asking just what was this negative sentiment for which an expression of amazement was considered a more polite alternative. However, that would probably be unproductive. Instead, I would be much more interested to learn whether my explanation as to why there is really no cause for amazement made any impression on you. You have not responded to it. Was that just you trying to be polite again?

    Liked by 1 person

  30. John,
    Well, this issue has been discussed so much on blogs over the years that it’s hard to see how repeating these discussion will achieve a different outcome. Also, there are now many millenial temperature reconstructions that all produce broadly the same results. As I understand it, there is very strong agreement about the basic picture (slow cooling towards what is referred to as the Little Ice Age and then warming since the mid-1800s to today). Most of the more recent work (as far as I’m aware) has been focussed more on the shorter timescale variability than on the longer-term picture.

    Also, although statistics is clearly something that researchers sometimes apply incorrectly, if others think it has significantly influenced the results in some field then the solution is, ideally, to redo the work in a way that correctly applies the statistics. Just asking questions is unlikely to resolve this. Also, there have now been so many temperature reconstructions that all produce the same basic picture that it seems very unlikely that this is some kind of major issue.


  31. ATTP,

    Thank you for your response. However, I don’t think it is addressing my point and I suspect it rather begs the issue. The question is, how is it that, despite what you say, there are still those (seemingly intelligent) people who can remain concerned, and is this fact really reason enough for your amazement? The problem is that you are saying that a consilience should be reason enough to dismiss people who are concerned. But these people are concerned precisely because they fear that the consilience is not as significant as it seems. Simply saying that there is an impressive consilience, and those who remain concerned should stop complaining and do their own work, doesn’t help because:

    a) You are often dealing with lay people who may have enough background to be concerned, but not enough to become properly involved. Insisting that they put up or shut up is tantamount to demanding deference without doing anything to help such people become comfortable with such deference.

    b) Knowing that, in general, a result may be highly sensitive to preselection of data and the statistical approach taken, one might reasonably expect that this is also true of paleoclimatology. That being the case, the professed consilience starts to look like something that needs an explanation rather than something that explains. To what extent is an underlying truth driving the consilience, rather than a presupposition of truth generating conciliation via statistical artefact?

    c) If a sceptic were to have the acumen to do their own analyses, then (having sufficient room for manoeuvre) one might reasonably expect that they could draw conclusions that differ from the consensus. But how does that help? Is whether or not a technique reproduces other people’s results a good enough criterion for validating the technique? Isn’t experimenter bias supposed to be all about why such a criterion should be treated with suspicion?

    Once again, I feel I should make it clear that I am not arguing that the consensus within paleoclimatology is wrong, but that it is at least reasonable to challenge the consensus with experimenter bias in mind. We are dealing with a subject (statistics) where the correct pre-selection of data is critical and results can differ wildly under different statistical approaches. Add to that the pre-existence of a received wisdom, and I think the extent to which consensus is the result of genuine consilience becomes a reasonable matter for debate. Put another way, can experimenter bias become institutionalised?


  32. Oh, I see, you’re more asking why are there still intelligent people who remain concerned. I don’t have a particularly good answer. As to your other points.

    a) I’m certainly not insisting that people who are concerned put up, or shut up. However, I don’t think there is some obligation that all people’s concerns are addressed. I think trying to engage with people who are concerned is good, but there is a limit. I also tend to think that people can’t both be lay-people who are just concerned, and people who have enough expertise to actually question the science. The latter can’t simply go “but I’m just a lay person” when they get pushback (IMO, at least).

    b) I have no idea how this is resolved without simply doing more research. If what’s been done isn’t good enough for some people, then either they can advocate for more research, do so themselves, or simply accept that they won’t be satisfied.

    c) I think this is how science progresses. If someone gets a result that seems different to what other have got, then it may provide an opportunity. However, it does have to be credible.


  33. ATTP,

    >”Oh, I see, you’re more asking why are there still intelligent people who remain concerned. I don’t have a particularly good answer.”

    And whilst that remains the case, perhaps you should remain open-minded.

    >”I’m certainly not insisting that people who are concerned put up, or shut up.”

    Fine, but it sounded to me as though that is what you were doing here when you said:

    “Also, although statistics is clearly something that researchers sometimes apply incorrectly, if others think it has significantly influenced the results in some field then the solution is, ideally, to redo the work in a way that correctly applies the statistics. Just asking questions is unlikely to resolve this.”

    >”However, I don’t think there is some obligation that all people’s concerns are addressed.”

    Nor would I expect you to feel so obliged.

    >”I also tend to think that people can’t both be lay-people who are just concerned, and people who have enough expertise to actually question the science.”

    I’m not sure what you are getting at here. I would have thought it eminently possible for non-experts to have enough about them to challenge experts. It happens in life all the time.

    >”I have no idea how this is resolved without simply doing more research.”

    If the suspicion is that experimenter bias has become institutionalised, then this may be of limited help.

    >”However, it does have to be credible.”

    And there’s the rub. How is the credibility of a particular data pre-selection or choice of statistical technique to be determined? One would hope that it would have nothing to do with them giving the answer that is expected.


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