The Trick

For the benefit of new readers, we discussed some aspects of the “trick” at Climate Audit in the past. Obviously, the Climategate Letters clarify many things that were murky in the past. On the left is a blowup of IPCC 2001 Fig 2.21 showing where the Briffa reconstruction (green) ends. More on this below.

Figure 1 below is the original graphic showing the MBH98-99, Jones et al 1998 and Briffa 2000 temperature reconstructions. I think that it’s fair to say that this graphic gives a strong rhetorical impression of the proxy reconstructions all going up throughout the 20th century, lending credibility to the idea that the “proxy” reconstructions would also be responsive to past warm periods – and obviously not giving any “fodder to the skeptics” by revealing the divergence between the Briffa reconstruction and temperatures.

Figure 1. IPCC 2001 Comparison of warm-season (Jones et al., 1998) and annual mean (Mann et al., 1998, 1999) multi-proxy-based and warm season tree-ring-based (Briffa, 2000) millennial Northern Hemisphere temperature reconstructions. The recent instrumental annual mean Northern Hemisphere temperature record to 1999 is shown for comparison.

While the digital version of the Briffa reconstruction has only become available in the past few days, Briffa 2000 (cited in the caption to IPCC Fig 2.21) did show the decline as shown in Briffa 2000 Figure 5 shown below (with its original caption). This series obviously goes down at the end (as does a related series in Briffa et al 1998, referred to by Gavin Schmidt.) What Gavin didn’t discuss is how you get from the version below to the IPCC version.

Figure 2. Briffa 2000 Figure 5 An indication of growing season temperature changes across the whole of the northern boreal forest. The histogram indicates yearly averages of maximum ring density at nearly 400 sites around the globe, with the upper curve highlighting multidecadal temperature changes… The LFD curve indicates low-frequency density changes produced by processing the original data in a manner designed to preserve long-timescale temperature signals (Briffa et al., 1998c). Note the recent disparity in density and measured temperatures discussed in Briffa et al., 1998a, 1999b). Note that the right hand axis scale refers only to the high-frequency density data.

Gavin Schmidt stated that everything was “in plain sight”. Regular CA readers are used to watching the pea under the thimble. There is no mention in the IPCC report of the deletion of Briffa reconstruction data after 1960. Nor is there any mention of the deletion in the IPCC reference (Briffa 2000) nor, for that matter, in the article cited by Gavin Schmidt (Briffa et al 1998). These articles report the divergence, but do not delete it. (Briffa et al 2001 does delete the post-1960 values.)

Not only was the deletion of post-1960 values not reported by IPCC, as Gavin Schmidt implies, it is not all that easy to notice that the Briffa reconstruction ends around 1960. As the figure is drawn, the 1960 endpoint of the Briffa reconstruction is located underneath other series; even an attentive reader easily missed the fact that no values are shown after 1960. The decline is not “hidden in plain view”; it is “hidden” plain and simple.

Figure 3. Blowup of IPCC Figure 2-21.

Previous discussion of these issues is at Climate Audit here here here and more recently by Jean S here. Jean S and UC report at CA that the puzzling end point properties can be replicated by replacing actual proxy data after 1960 with instrumental data and then smoothing (truncating back to 1960) – exacerbating the problem. (I haven’t personally confirmed this, but Jean S and UC are extraordinarily skilled analysts and know this material as well as I do.) Jean S:

In order to smooth those time series one needs to “pad” the series beyond the end time, and no matter what method one uses, this leads to a smoothed graph pointing downwards in the end whereas the smoothed instrumental series is pointing upwards — a divergence. So Mann’s solution was to use the instrumental record for padding, which changes the smoothed series to point upwards as clearly seen in UC’s figure (violet original, green without “Mike’s Nature trick”).

Jean S then drolly quoted Mann:

No researchers in this field have ever, to our knowledge, “grafted the thermometer record onto” any reconstruction. It is somewhat disappointing to find this specious claim (which we usually find originating from industry-funded climate disinformation websites) appearing in this forum.

The Climategate Letters contain a very interesting discussion between Mann, Jones, Briffa, Karl and Folland worrying that showing the discrepancy would provide “fodder to the skeptics”. More on this tomorrow.


  1. Mike Smith
    Posted Nov 26, 2009 at 8:35 PM | Permalink

    Thanks for your diligence and thick skin.

  2. Fred
    Posted Nov 26, 2009 at 9:12 PM | Permalink

    An old adage . . . the best place to hide a car in plain sight is in a parking lot.

    So it makes sense the best best to hide a proxy squiggle in plain sight is under a bunch of of other proxy squiggles.

  3. Arnold
    Posted Nov 26, 2009 at 9:18 PM | Permalink

    If i can direct you to something, if i look at the different websites, there is not only a adjustment in the data after 1960, there is adjustment from the 1930,s onwarts

  4. Nick Stokes
    Posted Nov 26, 2009 at 9:19 PM | Permalink

    It is not true that “Gavin Schmidt stated that everything was “in plain sight”.” He said:
    Those authors have always recommend not using the post 1960 part of their reconstruction, and so while ‘hiding’ is probably a poor choice of words (since it is ‘hidden’ in plain sight), not using the data in the plot is completely appropriate, as is further research to understand why this happen
    He was talking specifically about Jones’ description of what is done in his paper, to which he applied the word “hiding”.

    Steve: Gavin’s statement is untrue. There are no such recommendations in Briffa et al 1998 or Briffa 2000. The “recommendation” seems to have evolved out of the preparation of the IPCC 2001 spaghetti graphic – something that I’ll discuss tomorrow.

  5. MrPete
    Posted Nov 26, 2009 at 9:21 PM | Permalink

    Fred, they didn’t hide the squiggle under the others.

    They hid the premature CUTOFF of the squiggle under the others.

  6. Reader
    Posted Nov 26, 2009 at 9:27 PM | Permalink

    Mike ‘the man’ Mann has just published another first author paper in Science. The stuff he is talking about just makes me dizzy. I find it very amazing for people to use not-so-good proxy data coupled with not-even-close-to-reality GCMs to study past a thousand years of global temperature. This kind of climate science (I call, the unknown-unverifiable-unrepeatable past temperature reconstruction) is just not science at all. The same applies to the future ‘projection’ of climate models. If one just get all the model projection data from 80’s about future 100 years climate I bet the ‘future’ has changed dramatically. This is clearly not science. The most fundamental thing about science is repeatable. This is merely a guessing game at this stage. The so-called paleclimate study with no-very-reliable proxy data is even worse.

  7. Posted Nov 26, 2009 at 9:44 PM | Permalink

    Nick Stokes:

    To be clear, whatever Gavin meant by

    ‘hidden’ in plain sight

    are also you saying that he, Mann and the others were right to refuse anyone the data from 1960? That it’s a ‘travesty’, perhaps, that Steve McIntyre has the data even in 2009, courtesy of anon of UEA? (For whom we pray safety, I suggest, even as we are deeply thankful for what they did.)

  8. Posted Nov 26, 2009 at 9:55 PM | Permalink

    What about the possibility that the proxy data is correct and the thermometer is wrong and we have been cooling for years (and the satellite data turns out to be calibrated against contaminated ground measurements) ?


    Steve– Nope.

  9. bender
    Posted Nov 26, 2009 at 9:55 PM | Permalink

    The divergence was hidden, both graphically and via data suppression and distortion. It was intentional. It was planned. They did it despite IPCC reviewer suggestions to the contrary. Why over-rule the reviewer’s suggestions? They did it for a reason: to suppress inquiry into how reliable these tree rings are as a temperature proxy. Case closed.
    Now … Why do you think they dodged Dr. Keiller’s great questions?

  10. TerryMN
    Posted Nov 26, 2009 at 9:57 PM | Permalink

    Nick – Briffa’s dendro proxies do not agree with the most recent (and so one would think most accurate) instrument record for one of two reasons: either they’re (as constructed) not reliable temperature proxies to begin with, or the most recent instrument record is not accurate. Which do you think it is – the former or the latter (or some of both)?

  11. anon
    Posted Nov 26, 2009 at 10:00 PM | Permalink

    This is getting ridiculous. It’s amazing that people have been able to converse in english for the past 400 years. We’ll use a trick to hide the decline. We’re not hiding any decline, it’s right there! What’s right there? The missing decline. I don’t see any missing decline. Exactly. This is turning into a who’s on first routine. Climate science sucks. From now on, get them on the stand and remove all wiggle room.

  12. Rhoda R
    Posted Nov 26, 2009 at 10:16 PM | Permalink

    This Gavin fellow seems to be really proud of the way they’ve hidden the data.

  13. Posted Nov 26, 2009 at 10:23 PM | Permalink

    If you don’t mind, this is not getting ridiculous —- It is ridiculous.

    I will never get past the fact that in Mann 08 the non-hockeystick curves are thrown out and the hockey stick shapes are kept. Who the hell would ever pass that through peer review!!

  14. Andy
    Posted Nov 26, 2009 at 10:27 PM | Permalink

    The instrumental temperature in the graph. Does that refer to satellite data or ground station records?

  15. Nick Stokes
    Posted Nov 26, 2009 at 10:27 PM | Permalink

    The issue of divergence has been discussed at great length in the literature. Briffa et al 1998 was an early one. I don’t think Steve would appreciate diverting the thread into that topic.
    I was talking about Gavin’s characterisation of Jones paper.
    and RD,
    I don’t think 1960 was a dividing line for data availability. It’s an issue of what it was appropriate to plot. Again, this is the much discussed divergence issue. This para from Briffa et al 2004 sums up the 1960 issue in a review paper:
    The above facts seem to support an inference that some slowly varying factor began to exert a very widespread negative influence on the trend of these MXD data from around the middle of the 20th century, with effects at higher frequency also becoming noticeable in some high-latitude regions. For the time being, we circumvent this problem by restricting the calibration of the density data to the period before 1960. This reduces the potential overlap between temperature observations and density measurements and means that less data can be reserved for independent tests of the validity of predictive equations. This situation is far from ideal, but the alternative, using data after 1960 and thus incorporating non-temperature- related bias when fitting regression equations as a function of density variability, would invariability produce earlier estimates of past temperature that, to some extent, too warm.

    Steve: This isn’t an “explanation” – it’s no more than arm waving.

  16. kse
    Posted Nov 26, 2009 at 10:38 PM | Permalink

    Has anyone been able to figure out how Harry the Plotter mangled WMO codes and station coordinates?

    I had an idea to do some comparison between and data from NOAA and GISS – but I blew all my fuses in hour or so. Anyhow, managed test one weather station (so called Helsinki/Seutula that has same WMO code as Helsinki-Vantaa airport, but has measurement history back to 1829 or 1880 depending on the source… while the airport and its weather station become operational in 1952).

    It seems like CRU has “added” some “value” to their statistics:

    …and if we look at the difference of the mean temperatures between, e.g., CRU and NOAA data we can see quite revealing marks of ADM (Anthropogenic Data Manipulation):


  17. Raven
    Posted Nov 26, 2009 at 10:47 PM | Permalink

    2009 November 26 Nick Stokes,

    What are the above facts that “seem to support an inference that some slowly varying factor”?

    How do they hold up when you take this paper into account:

  18. Paul Penrose
    Posted Nov 26, 2009 at 10:50 PM | Permalink

    So the story is this: We know the data before 1960 are fine, so we use that, but since the data from 1960 onward are obviously bad, we just don’t use that. Is that what they are saying? What a bunch of pretentious crap! You can’t just drop part of the data and claim it’s corrupted unless you can explain exactly how it became corrupted. Otherwise you can’t know for sure that the rest of the data (the pre-1960 portion in this case) is not corrupted as well. Without that explanation you must throw out all the data. If you are interested in doing real science that is.

  19. Gavin (Not Schmidt)
    Posted Nov 26, 2009 at 10:51 PM | Permalink

    Check this out! CRU source code and dirty “tricks” in a nut shell, explained a software developer.

    Steve: There’s a lot of piling on right now. This particular issue is limited to the Briffa density reconstruction. This is not part of a climate “model” as generally understood or part of the CRU temperature series.

  20. stevemcintyre
    Posted Nov 26, 2009 at 11:02 PM | Permalink

    Readers interested in the topic may be interested in a post that I wrote in Feb 2006, just after the publication of Osborn and Briffa 2006, in which I reviewed some of these cargo cult ideas in Briffa’s articles

    Here’s one of my favorite Team explanations – one that I’ve described elsewhere as “cargo cult”:

    In the absence of a substantiated explanation for the decline, we make the assumption that it is likely to be a response to some kind of recent anthropogenic forcing. On the basis of this assumption, the pre-twentieth century part of the reconstructions can be considered to be free from similar events and thus accurately represent past temperature variability.

    D’Arrigo has mooted the possibility that moisture limitations have affected growth under warmer temperature regimes. Botanical response curves are upside-down U-shaped curves and there is no reason to expect a linear response of ring widths to an arbitrary temperature increase. Nonetheless the linearity assumption is embedded into the methodology. Craig Loehle published an article in Climatic Change formalizing this point – which has also been discussed at CA on a number of occasions.

  21. TerryMN
    Posted Nov 26, 2009 at 11:03 PM | Permalink

    The above facts seem to support an inference that some slowly varying factor began to exert a very widespread negative influence on the trend of these MXD data from around the middle of the 20th century

    Since the science is settled, and you’re obviously much more versed in this issue than I – can you explain to me what factor it is he’s referencing? Please?

  22. Al
    Posted Nov 26, 2009 at 11:11 PM | Permalink

    Translation of the quote from Briffa 2004:
    Something is happening and we don’t know what. We don’t know if it happened prior to the calibration period either. Please deprecate all temperature reconstructions outside of our calibration period as we’ve just proven (in the peer reviewed literature) that the same tree can provide both an excellent temperature response – and an abysmal one.

    Well, that last point was hidden, just like the decline.

  23. marie elks
    Posted Nov 26, 2009 at 11:22 PM | Permalink


    [i]It’s an issue of what it was appropriate to plot.[/i]

    Precisely. The tree rings are useless for any time period by CRU’s own admission, hence they are not and never have been “appropriate to plot.” Yet they did and continue to do so. Why?

  24. Nick Stokes
    Posted Nov 26, 2009 at 11:28 PM | Permalink
    Raven, TerryMN
    The Briffa review goes on to consider ozone as a possible cause.
    Paul P,
    One of the Briffa plots of evidence is shown in this CA thread. The onset of divergence at about 1960 is marked.
    You are making a general criticism of dendro, and its divergence issue, which has been long discussed at CA. I think the focus here is on whether the presentation was properly described in the papers.

    Steve: It wasn’t mentioned in IPCC TAR or in the first two drafts of IPCC AR4 nor was it referred to by any dendro reviewer of the AR4 Second Draft.

  25. Craig Loehle
    Posted Nov 26, 2009 at 11:36 PM | Permalink

    It may be appropriate to HYPOTHESIZE that something is different about the tree rings after 1960, but there is no way you can use this as a proof of anything (like unprecedentedness, for example). Briffa’s guess about this divergence should not form a basis for world energy policy.

    Raven: thanks for plugging my paper.

  26. geo
    Posted Nov 26, 2009 at 11:56 PM | Permalink

    Thanks for the 2006 link, Steve.

    “In the absence of a substantiated explanation for the decline, we make the assumption that it is likely to be a response to some kind of recent anthropogenic forcing.”

    I’m torn between feeling appalled and feeling “well, that’s what they do, isn’t it?”.

    Algebra is one of the great inventions of the human race. Alas, it only works when you’ve actually identified all the variables. Otherwise it is just garbage.

    I’d still love to see someone try on for size what happens to the MWP if you assume that the reduced tree ring growth in the late 20th century is a response to hitting a temp threshold, and then apply the “divergence” on that basis to MWP reconstructions.

  27. John Blake
    Posted Nov 27, 2009 at 12:31 AM | Permalink

    snip – this sort of angry comment is against blog policy

  28. Nick Stokes
    Posted Nov 27, 2009 at 12:32 AM | Permalink

    Craig Loehle
    Briffa’s guess about this divergence should not form a basis for world energy policy.
    It doesn’t – not by a long stretch. Kyoto happened in 1990. The primary basis of AGW concern is the accumulation of GHG and their known radiative properties.

    Steve: Nick and Craig, as you well know, editorial policy here discourages efforts to debate the “big picture” in one paragraph bites. Otherwise every thread becomes identical. LEt’s leave it there, please

  29. TerryMN
    Posted Nov 27, 2009 at 12:43 AM | Permalink

    snip = OT
    In *your* opinion, is the divergence problem an increase in lower atmospheric O3, or a decrease in stratospheric O3? And why?

  30. TerryMN
    Posted Nov 27, 2009 at 12:52 AM | Permalink

    Steve – I understand the snip, but would like to note that was started with:


    So as to avoid confusion. Thanks.

  31. marie elks
    Posted Nov 27, 2009 at 12:55 AM | Permalink

    Not sure where to put this, but in the fisher.txt file within the documents folder is found the following:

    LOL “Alderheimers”????


    I will send you the time series you need in a minute for the Central
    west Greenland Stack…
    And some other bits and pieces,,, The NGRIP record has the trend in it
    that is no doubt closer to the truth for the fixed elevation temperature
    history. But even there one could need a correction for elevation
    change. The elevation corrected south GRIP Holocene has a very strong
    negative delta trend in it and I expect there should be some correction
    done to the north GRIP record too,, eventually I think they should all
    come out looking like our records from Northern Canada. Now at least
    ice core records have some low frequencies to correct… not like your
    bloody trees that can not remember one century to the next,,,
    (alderheimers )

    So the files attached have the same names as in the papers :
    1. “Signal and Noise ….conductivity” Fisher.1994 .Holocene,4,2,
    2. “Intercomparison of….techniques”, Fisher and others.1996. Nato
    ASI Vol 141, “Climate variations and forcingmechanisms of the last
    2000 yrs”, Springer Verlag etc. pp 297-328.

    The papers act as the user manual and file discription. There are
    Greenland files : central Greenland O-18 stack DELNORM6.CWG

    Fritz Koerner and I down to do a chapter in the book too I think,if
    its the same book ,but its not due for quite a while,,,


    Keith Briffa wrote:
    > Dave
    > I am currently working with Ray Bradley and others to produce a chapter for
    > a PAGES book . Our chapter is concerned with the climate of the last 1000
    > years and I am currently putting together a Figure and text concerned with
    > the circum North Atlantic area. I wondered if you had , in an easily
    > plotable form )i.e. spreadshhet-like numbers with real dates ) the stacked
    > record – or whether you considered just plotting the GRIP?GISP mean was
    > appropriate ? In a paper by Hammer , the north and south GRIP records (O18)
    > are different – with a negative trend through the Holocene in the north and
    > a recent “warming”, but neither at summit. I have restricted space so what
    > is best to plot .
    > cheers
    > Keith

  32. marie elks
    Posted Nov 27, 2009 at 1:14 AM | Permalink

    Wow, Mr Steve, were you aware of a University of Albany inquiry into two papers produced by a Dr Wang? Apparently, station data was determined to be reported VERY inaccurately in two published papers.

    The file name is 080214_SUNYA_draft.pdf and the document date is Feb 14, 2008.

    The PDF is text-protected so I can’t paste sections here, but the inquiry committee unanimously voted to send it to an investigating committee.

    Wow. Just wow.

    Steve: the problems with this data set were initially reported at Climate Audit though the later course of actions were not ones that I would have taken.

  33. Nick Stokes
    Posted Nov 27, 2009 at 1:33 AM | Permalink

    Clearly we’re straying – I’ll just refer to the Briffa 2004 paper. I’m no authority here.

  34. marie elks
    Posted Nov 27, 2009 at 1:53 AM | Permalink

    Just curious, did the revisions listed below make it to the published paper? This is the first email in the 1154697504.txt file.

    Mr Steve, did you consider contacting this Anders fellow for a contributor here? He sounds at least minimally interested in accuracy.


    From: Anders Moberg
    To: Martin Juckes
    Subject: McIntyre, McKitrick & MITRIE …
    Date: Fri, 04 Aug 2006 09:18:24 +0100

    Dear Martin and all others,

    Having read the new manuscript, I would like to draw the attention of
    all of you to the section about McIntyre&McKitrick vs Mann et al. I am
    not entirely happy with this section. It may be that I am not fully
    updated about all details on their dispute, but it appears to be some
    mistakes in this section of our manuscript. Therefore, I ask all of you
    to check how this section can be improved and clarified. This is very
    important! If we refer incorrectly to the MM-Mann dispute, I am
    convinced that all of us will be involved in lengthy frustrating e-mail
    discussions later on. I anticipiate this from personal experience! Let’s
    do our best to avoid this.

    The problematic bit of text starts on p. 16, para 4: (“The failure of
    MM2003 … is partly due to a misunderstanding of the stepwise
    reconstruction method”) and slightly below: (“MM2003 only calculate
    principal components for the period when all chronologies are present”).

    I read through the MM2003 paper yesterday. From what is written there,
    on p. 763-765, it appears that they were well aware of the stepwise
    method. On p. 763, about at the middle of the page, they write:
    “Following the description of MBH98 … our construction is done
    piecewise for each of the periods listed in Table 8, using the roster of
    proxies available through the period and the selection of TPCs for each
    period listed in Table 8”.

    This is clearly at odds to what is written in our manuscript. Has it
    been documented somewhere else that MM2003, despite what they wrote,
    really misunderstood the stepwise technique? If it is so, we need to
    insert a reference. If this is not the case, we need to omit the lines
    about the misunderstanding. We also need to explain better why the
    MM2003 calculations differ from MBH.

    Moreover, our sentence (“MM2003 only calculate principal components for
    the period when all chronologies are present”) imply that MM2003 only
    calculated PCs for the period 1820-1971, as this would be the period
    when all chronologies are present according to the MM2003 Table 8.
    Obviously, they calculated PCs beyond 1820, as their calculations
    actually extend back to 1400.

    The problem continues in the legend to our Fig. 2. (” Each of the 212
    data series is shown … The red rectangle indicates the single block
    used by MM2003, neglecting all data prior to 1619″). The last sentence
    is inconsistent with the information in MM2003 in three ways; a) MM2003
    clearly show in their Table 8 that they analysed the same blocks of data
    as MBH. b) The year 1619 as a starting point of a data block is
    inconsistent with MM Table 8. Where does the year 1619 come from? It is
    not mentioned anywhere in MM2003. c). The red block implies that MM2003
    made calculations back only to 1619, but they did back to 1400.

    Moreover, the numbers given in the graph of our Fig. 2 indicate that the
    total number of series is 211, whereas the text in the legend and also
    in the main text on p. 16 says 212. Which number is correct?

    I suppose that some of you others will know this subject much better
    than I. I have just read the MM2003 paper, and find our reference to it
    to be inconsistent with it. I hope you all can make efforts to make this
    bit crystal clear. If not, I fear we will get problems!

    Finally, I would like to draw your attention to the related sentence in
    our conclusions on p. 26: (“Papers which claim to refute … have been
    reviewed and found to contain serious flaws”). Are all of you happy with
    this statement? Would it sound better with a somewhat less offending
    sentence, something like:

    “Papers which claim to refute … have been reviewed and found to
    essentially contribute with insignificant information that does not
    affect the consensus, and even to include some flaws.”

    I attach the MM2003 paper.

    I will send some comments to the other parts of the text in a separate mail.


  35. Posted Nov 27, 2009 at 2:32 AM | Permalink


    I read your post here on the trick and also the one on WUWT.

    I believe I found a fairly large error in your reading of Mann’s mail…

    You misread that last email (link) and you’re on the wrong divergence.

    The meat:

    So, if we show Keith’s series in this plot, we have to comment that
    “something else” is responsible for the discrepancies in this case. Perhaps
    Keith can
    help us out a bit by explaining the processing that went into the series
    and the potential factors that might lead to it being “warmer” than the Jones
    et al and Mann et al series??

    As I read it, he is not talking about the post 1960 decline as that would be cooler not warmer.

    Here Keith is warmer than everyone. Now read this from a few paragraphs previous:

    We demonstrate
    (through comparining an exatropical averaging of our nothern hemisphere
    patterns with Phil’s more extratropical series) that the major
    discrepancies between Phil’s and our series can be explained in terms of
    spatial sampling/latitudinal emphasis (seasonality seems to be secondary
    here, but probably explains much of the residual differences). But that
    explanation certainly can’t rectify why Keith’s series, which has similar
    *and* latitudinal emphasis to Phil’s series, differs in large part in
    exactly the opposite direction that Phil’s does from ours.

    So Briffa is warmer than Mann and Phil is in the opposite direction. Looking at the chart he must be talking about 1800-1900 here and saying they gotta have a good explanation for it.

    You’re dead right they deleted post 1960 data etc… but this email does not provide the motive for it.

    [Although Ironically I think it really does. 😉 The motives are the same and we know that.]

    But technically it is unfair to say Mann is talking about post 1960 in this email.


  36. Ric
    Posted Nov 27, 2009 at 2:44 AM | Permalink

    Okay…to the layperson. The hockeystick just does not make sense. The indication of the Hockeystick graph is that is was so damn cold before 1900 that the world must have been covered in glaciers before. Okay maybe I don’t read the graph well. But think of this from my point of view. From the 70’s to the middle 90’s I remember staggering snowfalls and brutal cold. ( I live in MN ). If the graph is correct…up until 1900 it was so damn cold that it had to be unbearable here. If you go back to the ” little ice age” between mid 1500 to mid 1700 how in the world could anyone live in anyplace north of the equator? And then it just warms starting 1900? And then it was hospitipal in the northern climate? In fact now it just skyrockets? I know what I am saying seems ignorant….but the hockeystick chart makes it seem like such a huge temperature shift that one would have to assume that it had to be much colder….not just a little….you have to ask yourself…how the hell did we grow crops before 1900 in Minnesota?

  37. Spence_UK
    Posted Nov 27, 2009 at 3:14 AM | Permalink

    Mann responds to the “trick” over at DeSmogBlog – and he can’t resist continuing to be tricky, even after the cover is blown.

    He claims the “trick” was adding the instrumental data as a second, separate line on the graph for comparison (and to show recent temperatures). Of course, thanks to UC and Jean S we know that this just isn’t true. And it is obviously not true – the graphic being referred to (on the WMO statement) doesn’t even have a separate instrumental temperature line! (See Jean S’ post at the original CA here)

    He then refers to the “hide the decline” as being the trimming of the post-1960 data, which is a half-truth, conveniently forgetting the extended splice remix.

    I notice some of the pro-team blogs are simply parroting these foolish, incorrect claims; I ended up at John Cook’s place via Lambert’s which contains an similarly misleading description.

  38. Posted Nov 27, 2009 at 4:43 AM | Permalink

    I have clarified what Tamino is showing on his web site ( His 30 year moving average was not compressed, just slid back 15 years to the wrong date. It starts 15 years after 1600 instead of 30 years after:

  39. Posted Nov 27, 2009 at 4:43 AM | Permalink

    I have clarified what Tamino is showing on his web site ( His 30 year moving average was not compressed, just slid back 15 years to the wrong date. It starts 15 years after 1660 instead of 30 years after:

  40. Posted Nov 27, 2009 at 5:18 AM | Permalink

    The black curve in Gig.2 marked as temperature record since 1880 is quite suprising. I think it is pretty good estimation of real global temperature, showing that 2000s were just a bit warmer than 4Oties. GISTEMP or HadCRUT show the difference at least three times bigger. Where does it come from?

  41. ignoranceisntbliss
    Posted Nov 27, 2009 at 6:15 AM | Permalink

  42. Kent
    Posted Nov 27, 2009 at 7:35 AM | Permalink

    If the word “trick” is commonly used by scientists to describe a clever, albeit legitimate, method of dealing with data then the word “trick” should pop up in numerous emails from climate scientists and in numerous contexts. Has anyone conducted a word count for “trick” within the stolen emails?

    Although I have heard non-scientists use similar phrases (e.g., “the trick to opening the jar of pickles is to pour hot water over the lid”) I have never heard of any scientist using the phrase to describe his/her research methodology.

  43. Posted Nov 27, 2009 at 7:43 AM | Permalink

    MODERATOR: Please reject my Tamino posts. They were preliminary work for which I will have a professional graphic made to explain in the next day or two. Thanks!

  44. steve
    Posted Nov 27, 2009 at 8:57 AM | Permalink

    If the tree rings are not a good predictor of actual observable temperatures ( which appears to be the case ) then to me this says we should be skeptical about using them to reconstruct past temperatures.

    Is there a better reconstruction of temperatures for the past 1000 years other than tree rings ? ( ice cores, water levels etc ).

  45. steve
    Posted Nov 27, 2009 at 8:59 AM | Permalink

    A “trick” can be used to referred to a “method” in mathematics.

  46. Phil A
    Posted Nov 27, 2009 at 9:15 AM | Permalink

    Sorry if this is an old questionj (and that I don’t have the wherewithal to chase it myself) but how universal a problem is this “divergence” in the proxies? Is it just the tree-rings or in other proxies too? In the tree-rings is it in all the trees or just some of the trees? And do the cherrypicked trees have more or less divergence than the trees they chose not to use?

  47. Al
    Posted Nov 27, 2009 at 12:11 PM | Permalink

    Juraj V,
    The official historical instrumental data itself keeps getting adjusted too. That is: the black line is just an older version.

  48. Posted Nov 27, 2009 at 12:28 PM | Permalink

    Three details
    (1) the earlier black temperature line has surely been tweaked by lowering 1940’s so that the final line shoots up when the vertical scale is adjusted up to make “hockeystick”. I seem to remember emails about this, SST issues and land issues.
    (2) the earlier black temperature line is shown as red in the final graph, so that unconsciously we splice it on to Jones’ red reconstruction.
    (3) we now know that the hidden decline went down, down, down. Yet that little green line ends with a hint of uptick. Where did THAT come from?

  49. Posted Nov 27, 2009 at 12:33 PM | Permalink

    Quick, quick,
    the span is spick.
    Right in the thick –
    a Hockeystick Trick.

  50. Shallow Climate
    Posted Nov 27, 2009 at 1:22 PM | Permalink

    Re Stevemcintyre, above: “Nonetheless, the linearity assumption is embedded into the methodology.” When I first read that statement, my mind read it as “…embedded into the mythology.” Now, I dare you to claim that your actual wording is more truthful than my wayward mind here.

  51. MikeN
    Posted Nov 27, 2009 at 3:35 PM | Permalink

    From a review on Amazon of The Book of Basketball

    *(My favorite is the table comparing performances for two guards from ages 22 through 24. Except for Allen Iverson he makes the “executive decision” to show ages 23-25 because AI “spent five months in jail and missed his senior year in high school.” Yeah…that’s not really how stats work. You can’t just toss the numbers you don’t like and pick the ones that support your argument. Well, obviously you CAN, but that’s cherry-picking, not statistics.)

  52. Andrew
    Posted Nov 27, 2009 at 3:40 PM | Permalink

    Thanks for stepping-back to explain the history of some of this stuff that has been covered in detail previously, but may not be well understood by those who are not intimately familiar.

    In a discussion on another website (not a climate one!) I was told that the divergence problem was well-known, and well-explained; not swept under the carpet. The divergence was attributed to Aerosol pollution and changes in solar radiation. I was pointed to this article (which I can’t read without a subscription).

    My question is: Aside from hiding the issue in various articles, are the causes actually well-understood? Why does it affect some tree series, and not others (eg. in the graph above, it looks like only Briffa’s series is affected).

    Secondly, the context of Mann’s original statement is important: It was actually:

    [Response: No researchers in this field have ever, to our knowledge, “grafted the thermometer record onto” any reconstruction. It is somewhat disappointing to find this specious claim (which we usually find originating from industry-funded climate disinformation websites) appearing in this forum. Most proxy reconstructions end somewhere around 1980, for the reasons discussed above. Often, as in the comparisons we show on this site, the instrumental record (which extends to present) is shown along with the reconstructions, and clearly distinguished from them (e.g. highlighted in red as here). Most studies seek to “validate” a reconstruction by showing that it independently reproduces instrumental estimates (e.g. early temperature data available during the 18th and 19th century) that were not used to ‘calibrate’ the proxy data. When this is done, it is indeed possible to quantitatively compare the instrumental record of the past few decades with earlier estimates from the proxy reconstruction, within the context of the estimated uncertainties in the reconstructed values (again see the comparisons here, with the instrumental record clearly distinguished in red, the proxy reconstructions indicated by e.g. blue or green, and the uncertainties indicated by shading). -mike]

    Now: There is a bit of a difference in context between ‘it is never grafted on’ and ‘it is shown on the same graph but clearly identified’.

    When you / Jean S refer to the “grafting”, is your concenr with the issue that the instrumental record was shown on the same graph (which gives the reader a false impression of significance), or that the instrumental record was actually used to smooth the proxy record?

  53. Nick Stokes
    Posted Nov 27, 2009 at 4:29 PM | Permalink

    Steve, kent
    One well-known math example that comes to mind is “Ewald’s trick”, which is perfectly sound math (just from the Poisson summation formula). Googling gives 70,400 hits.

    Steve: Nick, that’s neither here nor there. Because Ewald’s trick is legitimate doesn’t mean that hiding the inconvenient data is a legitimate “trick”.

  54. Neil Fisher
    Posted Nov 27, 2009 at 5:33 PM | Permalink

    If the Mann quote is accurate, then perhaps he can explain an article in New Scientist Magazine (28th Nov 2009, pp11 “Hacked archive provides fodder for climate sceptics”) where Fred Pearce reports that Mann told him “…the ‘trick’ was simply a published device to extend to the present a graph of temperatures derived from the analysis of tree ring data.This is done using real thermometer data”. Hmmm – sure sounds like what he denied “anyone” would do to me. Perhaps Fred Pearce misrepresented his position (it’s not a direct quote of Mann), but it sure doesn’t look good, does it?

  55. Posted Nov 27, 2009 at 6:31 PM | Permalink


    One well-known math example that comes to mind is “Ewald’s trick”, which is perfectly sound math (just from the Poisson summation formula). Googling gives 70,400 hits.

    So you say that the CRU “trick” is some kind of sound and common technique in climate science? What is its purpose? Can you describe how it works?

  56. Nick Stokes
    Posted Nov 28, 2009 at 12:24 AM | Permalink

    No, Michal, I didn’t say that.

  57. Posted Nov 28, 2009 at 1:38 PM | Permalink

    Just an interesting thing I noticed. At the UEA website, they’ve posted some responses. At the bottom of this page UEA response
    are two graphs, labeled as follows:

    The WMO1999 figure (top) with climate reconstructions and instrumental temperatures merged, and a version (bottom) with the climate reconstructions (coloured) and instrumental temperatures (annual & summer in black) shown separately.

    If you overlay the two graphs, it’s clear that the top graph, with the items “merged” has a higher end point than the instrumental line on the second graph. Any ideas as to how merging instrumental data points with lower climate reconstruction values results in datapoints that are higher than the instrumental values? See the overlay here:


    The faint blue line in the upper right corner is the “merged value”. The two original graphs are available at the UEA site for anyone to work with.

  58. Posted Nov 28, 2009 at 5:55 PM | Permalink

    Figure 3 is strikingly similar to the emblem Lady Gaga had painted on her face at her concert in Montreal last night.

    Coincidence? I think not!

  59. Posted Nov 30, 2009 at 1:04 AM | Permalink

    I’m sure the research and the blog itself have been rewarding, but I’m thinking that there must be some degree of satisfaction in the revelations this past week that vindicate your efforts to seek a broader level of understanding before rushing to judgement on climate change.

    I do not detect any signs of gloating on these pages, though you would certainly be forgiven for doing so. Although only an occasional visitor, I do drop by now and again for an update into this increasingly interesting debate and even contribute to it in my own humble way in my own blog (

    I wish you all the best in your efforts to promote a spirit of reasoned discourse. Blessed are the peacemakers!

  60. Daganstein
    Posted Nov 30, 2009 at 9:00 PM | Permalink

    Yes, finally, we know that the science is being hidden UNDER OTHER SCIENCE. How dare these scientists produce graphs that are sometimes hard to understand. Thank you Steve, for continuing to cherry pick climate science. One day, you will be able to build a very large cherry pie and we will all eat it and it will be delicious.

  61. mfellion
    Posted Dec 17, 2009 at 9:10 PM | Permalink

    I think I acidently put my question on the wrong page so I will try again. Looking at the hockey stick. I noticed there is a large grey area which narrows drastically after about 1912. It first starts narrowing about 1800. What is the gray area. The red line shoots up but it is unclear to me what is being measured? Finnally, I see they left out the tree ring data. Looking at what I believe is the tree ring data going back, it doesn’t seem to coorelate with anything, going up and down independently of the other three data sources. Is that a correct observation?

    Different issue. Read the blog.

  62. Mikkel R
    Posted Feb 27, 2010 at 7:29 AM | Permalink

    Two simple question. TAR mentions on page 133 that figure 2.21 depicts the uncertainty interval of Mann et al. 1999 (figure 2.20 in TAR).

    First question: Is it appropriate and “normal” practice to “craft” (as a matter of speaking) the uncertainty interval of one study on a figure depicting several studies?

    Second question: Had the Briffa series been depicted in its entirety it would obviously have shown a decline in that proxy diverging from the temperature record. But would it also have gone below the “grey area”?

    The reason for asking is that illustratively this would severely impact the feeling of “consensus” between reconstructions that figure 2.21. implicitly portray but would also very visually contradict the certainty placed on Mann et al. 1999 (figure 2.20.) which as we all know was included in the summary for policymakers.

  63. Mikkel
    Posted Feb 27, 2010 at 10:29 AM | Permalink

    To answer my own questions I refer to:

    Sry for asking about what had already been covered.

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