Section 1.2 Response

The terms of reference are as follows:

1.1 Examine the hacked e-mail exchanges, other relevant e-mail exchanges and any other information held at CRU to determine whether there is any evidence of the manipulation or suppression of data which is at odds with acceptable scientific practice and may therefore call into question any of the research outcomes.


1. The allegation of ignoring potential problems in deducing palaeotemperatures from tree ring data that might undermine the validity of the so-called “hockey-stick” curve. In the late 20th century, the correlation between the tree ring record and instrumental record of temperature change diverges from that for the earlier period. The cause of this divergence does not appear to be understood. If the method used to deduce temperatures from tree ring proxy metrics for the earlier tree ring record is applied to the late 20th century tree ring series, then declining temperatures would be deduced for the late 20th century. It is alleged that if the cause of divergence between the tree ring and instrumental temperature record is unknown, it may have existed in earlier periods.  Therefore if tree rings had similarly failed to reflect the warming of the early Middle Ages, they may significantly under- estimate the warming during the Medieval Warm Period, thus falsely enhancing the contrast between the recent warming and that earlier period.  (It is this contrast that has led to statements that the late 20th century warming is unprecedented during at least the last 1000 years.)


2 Does not the problem of divergence for the late 20th century record  invalidate the deduction of tree ring palaeotemperatures for the period prior to the instrumental record?


12 Responses to “Section 1.2 Response”

  1. Jimchip Says:

    There is an early assumption that the tree rings are GREAT when compared with instrumental records:

    0907695513 Oct 6, 1998 (Briffa to Overpeck, reponse to Overpeck)Peck: “4) About trees…. (Keith are you still reading?? – I sent this to Ed and >Brian too, since they might have insights). Has anyone examined how a >tree-ring recon degrades as a function of sample size back in time. I >always see the quality of dendro recons cast as GREAT vs.other proxies (and >they are) based on comparison with instrumental records. But, the dendro >records usually have the best sample replication in this same instrumental >period, and then tail off back in time.”

    0924030302, 13 Apr 1999 (Mann to Briffa/Osborn): “There are problems with the 2000 year series in terms of your definition of the baseline for comparing with the other series, and this differs quite a bit from what we are likely to be showing in IPCC. It appears that both the density NH reconstruction and your 2000 year long series fall at least 0.1C below the other series during the 20th century, and are probably running at least that much too cold the whole way through.”

    Some not correlated with temp:

    0927817076 May 27, 1999 (Tim Osborn to Orson Vandeplassche, cc.Briffa): “The individual curves (Tornetrask, Taimyr and Yamal) have not been calibrated against their local temperature records yet, and so only exist as standardised (or normalised) anomalies…”
    and “…Instead, a new calibration needs to be made, using ring-width only. This hasn’t been done yet, and – while it *might* be a simple linear regression – sometimes ring-widths from one year and from the previous year are used together as predictors, so I cannot guarantee that it will be a simple rescaling of the uncalibrated curve. Nevertheless, the uncalibrated curve *is* correlated with summer temperature, so it certainly provides useful information.
    The average of the three series was calibrated *after* they were averaged, and was calibrated against the April-September mean temperature over all land north of 20N. This was purely for comparison with the other curves shown in our Science piece; for this curve, this region is by no means the optimum, and the temperature anomalies would no doubt differ in magnitude if a regional temperature from northern Eurasia had been used instead. This offers one explanation of why the 650-750 warming differs from Briffa et al. (1992)”

    IPCC Lead Author Mann re: IPCC revisions Also 0938031546, 0938108842, 8938125745

    0938018124 22 Sep 1999 (Mann to Briffa, Folland, Jones): “I am perfectly amenable to keeping Keith’s series in the plot, and can ask Ian Macadam (Chris?) to add it to the plot he has been preparing (nobody liked my own color/plotting conventions so I’ve given up doing this myself). The key thing is making sure the series are vertically aligned in a reasonable way. I had been using the entire 20th century, but in the case of Keith’s, we need to align the first half of the 20th century w/ the corresponding mean values of the other series, due to the late 20th century decline….But that explanation certainly can’t rectify why Keith’s series, which has similar seasonality *and* latitudinal emphasis to Phil’s series, differs in large part in exactly the opposite direction that Phil’s does from ours. This is the problem we all picked up on (everyone in the room at IPCC was in agreement that this was a problem and a potential distraction/detraction from the reasonably concensus viewpoint we’d like to show w/ the Jones et al and Mann et al series.
    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?? We would need to put in a few words in this regard. Otherwise, the skeptics have an field day casting doubt on our ability to understand the factors that influence these estimates and, thus, can undermine faith in the paleoestimates. I don’t think that doubt is scientifically justified, and I’d hate to be the one to have to give it fodder!…SO I think we’re in the position to say/resolve somewhat more than, frankly, than Keith does, about the temperature history of the past millennium.”

    Mann quoted Briffa’s 9/22/99 Email: “Let me say that I don’t mind what you put in the policy makers >summary if there is a general concensus. However some general discussion >would be valuable . First , like Phil , I think that the supposed >separation of the tree-ring reconstruction from the others on the grounds >that it is not a true “multi-proxy” series is hard to justify…The multi proxy series (Mann et al . Jones >et al) supposedly represent annual and summer seasons respectively, and >both contain large proportions of tree-ring input. The latest tree-ring >density curve ( i.e. our data that have been processed to retain low >frequency information) shows more similarity to the other two series- as do >a number of other lower resolution data ( Bradley et al, Peck et al ., and >new Crowley series – see our recent Science piece) whether this represents >’TRUTH’ however is a difficult problem. I know Mike thinks his series is >the ‘best’ and he might be right – but he may also be too dismissive of >other data and possibly over confident in his (or should I say his use of >other’s). After all, the early ( pre-instrumental) data are much less >reliable as indicators of global temperature than is apparent in modern >calibrations that include them and when we don’t know the precise role of >particular proxies in the earlier portions of reconstruction it remains >problematic to assign genuine confidence limits at multidecadal and longer >timescales. I still contend that multiple regression against the recent >very trendy global mean series is potentially dangerous. You could >calibrate the proxies to any number of seasons , regardless of their true >optimum response . I do >believe , that it should not be taken as read that Mike’s series (or >Jone’s et al. for that matter) is THE CORRECT ONE. I prefer a Figure that >shows a multitude of reconstructions (e.g similar to that in my Science >piece). Incidently, arguing that any particular series is probably better >on the basis of what we now about glaciers or solar output is flaky indeed…I know there is pressure to present a >nice tidy story as regards ‘apparent unprecedented warming in a thousand >years or more in the proxy data’ but in reality the situation is not quite >so simple. We don’t have a lot of proxies that come right up to date and >those that do (at least a significant number of tree proxies ) some >unexpected changes in response that do not match the recent warming. I do >not think it wise that this issue be ignored in the chapter. For the record, I do believe that the proxy data do show unusually >warm conditions in recent decades. I am not sure that this unusual warming >is so clear in the summer responsive data. I believe that the recent warmth >was probably matched about 1000 years ago. I do not believe that global >mean annual temperatures have simply cooled progressively over thousands of >years as Mike appears to and I contend that that there is strong evidence >for major changes in climate over the Holocene (not Milankovich) that >require explanation and that could represent part of the current or future >background variability of our climate.”

    Folland quoted: “The tree ring results >>may still suffer from lack of multicentury time scale variance. This is >>probably the most important issue to resolve in Chapter 2 at present.”

    0963233839 10 Jul 2000 “Raymond S. Bradley” to Frank Oldfield (see also 3.2):
    “But there are real questions to be asked of the paleo reconstruction. First, I should point out that we calibrated versus 1902-1980, then “verified” the approach using an independent data set for 1854-1901. The results were good, giving me confidence that if we had a comparable proxy data set for post-1980 (we don’t!) our proxy-based reconstruction would capture that period well. Unfortunately, the proxy network we used has not been updated, and furthermore there are many/some/ tree ring sites where there has been a “decoupling” between the long-term relationship between climate and tree growth, so that things fall apart in recent decades….this makes it very difficult to demonstrate what I just claimed. We can only call on evidence from many other proxies for “unprecedented” states in recent years (e.g. glaciers, isotopes in tropical ice etc..). But there are (at least) two other problems — Keith Briffa points out that the very strong trend in the 20th century calibration period accounts for much of the success of our calibration and makes it unlikely that we would be able be able to reconstruct such an extraordinary period as the 1990s with much success…Indeed, in the verification period, the biggest “miss” was an apparently very warm year in the late 19th century that we did not get right at all. This makes criticisms of the “antis” difficult to respond to (they have not yet risen to this level of sophistication, but they are “on the scent”). Furthermore, it may be that Mann et al simply don’t have the long-term trend right, due to underestimation of low frequency info. in the (very few) proxies that we used. We tried to demonstrate that this was not a problem of the tree ring data we used by re-running the reconstruction with & without tree rings, and indeed the two efforts were very similar — but we could only do this back to about 1700. Whether we have the 1000 year trend right is far less certain (& one reason why I hedge my bets on whether there were any periods in Medieval times that might have been “warm”, to the irritation of my co-authors!). So, possibly if you crank up the trend over 1000 years, you find that the envelope of uncertainty is comparable with at least some of the future scenarios, which of course begs the question as to what the likely forcing was 1000 years ago.”

    0969618170 22 Sep 2000 (Malcom Hughes to Tom Crowley):
    “If you examine my Fig 1 closely you will see that the Campito record and Keith’s reconstruction from wood density are extraordinarily similar until 1850. After that they differ not only in the lack of long-term trend in Keith’s record, but in every other respect – the decadal-scale correlation breaks down. I tried to imply in my e-mail, but will now say it directly, that although a direct carbon dioxide effect is still the best candidate to explain this effect, it is far from proven. In any case, the relevant point is that there is no meaningful correlation with local temperature. Not all high-elevation tree-ring records from the West that might reflect temperature show this upward trend. It is only clear in the driest parts (western) of the region (the Great Basin), above about 3150 meters elevation, in trees old enough (>~800 years) to have lost most of their bark – ‘stripbark’ trees. As luck would have it, these are precisely the trees that give the chance to build temperature records for most of the Holocene. I am confident that, before AD1850, they do contain a record of decadal-scale growth season temperature variability. I am equally confident that, after that date, they are recording something else.”

    “Quoting tom crowley :

    > Dear Malcolm and Keith, > > as I discuss in my Ambio paper the “anomalous” late 19th century warming > also occurs in a LaMarche tree ring record from central Colorado, the > Urals > record of Briffa, and the east China phenological temperature record of > Zhu. > > Alpine glaciers also started to retreat in many regions around 1850, > with > 1/3 to 1/2 of their full retreat occurring before the warming that > commenced about 1920. > > The Overpeck et al Arctic synthesis also discusses warming before 1920 – > that record matches very closely the Mann et al reconstruction in other > details back to 1600. > > Unpublished work by us on coral trends also suggests slight warming > between > about 1850-1920. > > So, are you sure that some CO2 fertilization is responsible for this? > May > we not actually be seeing a warming?”

    1037241376 13 Nov 2002 “Ronald M. Lanner” to the listserv ITRDBFOR@LISTSERV.ARIZONA.EDU:
    “I find it frustrating that some dendrochronologists stubbornly see tree ring characteristics as being affected by climate. They are not. They are affected by cambial activity. Cambial activity is affected by internalities of tree behavior, mainly hormonal and nutrient fluxes in the crown. Those things are largely influenced by climatic factors. So there is quite a bit of slack between the climatic factor and the ring characteristic. Is this just negligible static? I doubt it. I see this as an oversight by dendrochronologists that weakens their credibility a tad among those knowledgable about tree growth. I also have a quarrel with the dogma of dendrochology that the cambium changes as the tree becomes senescent. I know of no data that trees senesce — that is, that they undergo changes due solely to aging. This started as forestry dogma, and was accepted by tree-ringers, who then corrected for it. I’m practically the only one who has systematically looked for evidence of senescence (with a Ph.D. student), and we could not find any in young to ancient bristlecones.”

    {Added 2/21/10: A minor reference from Lanner re his book on Bristlecone pines)

    1141398437 3 Mar 2006 (Overpeck to Briffa):
    >we do need to say something , but as I said in an earlier message ,
    >not without more consideration. We should not write something curt
    >on this – ditto the Co2 possible fertilisation . In the push to do
    >all this other stuff , we have had to leave it – to discuss later
    >how to include an uncertainty issues bit about recent environmental
    >mess ups . The D’arrigo paper is not convincing , but we have to do
    >some work to show why , instead of just saying this . The divergence
    >issue is NOT universal , and not unrelated to very recent period
    >bias arising from processing methods . It is VERY LIKELY not the
    >threshold problem D’Arrigo thinks”

    The above was in response to D’Arrigo’s presentation at the NRC panel:
    “>>>Know anything about the “divergence problem” in tree rings? R D’arrigo talked to the NRC yesterday. I didn’t get to talk to her afterward, but it looked to me that they have redrilled a bunch of the high-latitude tree rings that underlie almost all of the high-res reconstructions, and the tree rings are simply missing the post-1970s warming, with reasonably high confidence. She didn’t seem too worried, jubut she apparently has a paper st out in JGR. It looked to me like she had pretty well killed the hockey stick in public forum–they go out and look for the most-sensitive trees at the edge of the treeline, flying over lots and lots of trees that are lesss sensitive but quite nearby, and when things get a little warmer, the most-sensitive trees aren’t anymore, and so the trees miss the extreme warming of the recent times, and can’t reliably be counted as catching the extreme warmth of the MWP if there was extreme warmth then. Because as far as I can tell the hockey stick really was a tree-ring record, regardless of how it was labelled as multiproxy, this looks to me to be a really big deal. And, a big deal that may bite your chapter…

    1141849134 8 Mar 2006 (Overpeck to Briffa) Subject: Fwd: divergence:
    “For those just in on the issue raised by Richard. There is a paper
    written by Rosanne D’Arrigo that apparently casts serious doubt on
    the ability of tree ring data to reconstruct the full range of past
    temperature change – particularly temperatures above mid-20th century
    levels…>Peck–Thanks. The big issue may be that you don’t just have to convince me
    >now; if the NRC committee comes out as being strongly negative on the
    >hockey stick owing to RD’A’s talk, then the divergence between IPCC and NRC will be a big deal in the future regardless. The NRC committee is accepting comments now (I don’t know for how long)… As I noted, my observations of the NRC committee members suggest rather strongly to me that they now have serious doubts about tree-rings as paleothermometers (and I do, too…at least until someone shows me why this divergence problem really
    >doesn’t matter). –Richard”

  2. Jimchip Says:

    1051638938 4/29/03 Cook qutoed in Briffa to Cook. A longer chain mail:
    Hi Keith,
    Here is the new Esper plot with three different forms of regionalization: linear vs. nonlinear (as in the original paper), north vs. south as defined in the legend, and east vs. west (i.e. eastern hemisphere vs. western hemisphere). All of the series have been smoothed with a 50-yr spline after first averaging the annual values. The number of cores/chronologies are given in the legend in parentheses. Not surprisingly, the north and south chronologies deviate most in the post-1950 period. Before 1950 and back to about 1200 the series are remarkably similar (to me anyway). Prior to 1200 there is more
    chaos, perhaps because the number of chronologies have declined along with the within-chronology replication. However, there is still some evidence for spatially coherent above-average growth. I showed this plot at the Duke meeting. Karl Taylor actually told me that he thought it looked fairly convincing, i.e. that the low-frequency structure in the Esper series was not an artefact of the RCS method.

    1101243716 Nov 23, 2004 Briffa to v.Jones
    Don’t get hung up on the “decline or changing sensitivity issue” in trees . This is NOT a great problem in Scandinavia, Ural/Yamal and is anyway a divergence in trend and quite subtle and evident in wood density mostly. We are also of the opinion that it could be partly a statistical processing artifact – we are exploring this now. If you plough through my comments and suggestions and then return the text with specific requests of what you wish to do I will then try to oblige thursday

    1141930111 09 Mar 2006 Eystsrein Jansen to Jones, quoted:

    >Looking at the discussions after the NAS panel meeting we should expect focus now to be sidetracked from PC-analyses and over to the issue of bad proxies and divergence from temperature in the last 50 years. Thus this last aspect needs to be tackled more candidly in AR4 than in the SOD, and we need to discuss how to do this, soon. The Key expert here is Keith and I guess we should be able to assess the situation based on his and D´Arrigo´s work and the expertise at hand.

    Peck quoted:
    >>>I’m hearing about D’Arrigo’s splash from other sources (Richard Alley) – hope Keith et al., have good counter arguments.
    >>>best, peck

  3. Jimchip Says:


    From: Michael Mann
    To: “Thomas.R.Karl”
    Subject: Re: paper on smoothing
    Date: Fri, 29 Aug 2008 15:53:41 -0400

    >> Curtis Covey wrote:
    >>> Very interesting. Does it mean that the apparent leveling-off of
    >>> global mean surface temperature since the turn of the century is due to “artificial suppression of trends near the time series boundaries” ?

    Mann: yeah, its statistically real, but an artifact almost certainly of
    natural variability. As Josh Willis nicely pointed out in a recent
    interview, anyone citing this as a reason to doubt the reality of
    anthropogenic climate change is like a vegas roller thinking he can beat
    the system because he’s on a momentary winning streak…

  4. jimchip Says:

    I’ve talked recently about the phenomenon of cherry picking tree ring chronologies with upticks in the small-subset (10-20) compilations used in typical Hockey Team multiproxy studies (e.g. Jones et al 1998; Crowley and Lowery 2000, etc., most recently Osborn and Briffa, 2006; and to a slight lesser extent D’Arrigo et al, 2006 (where there was a discipline resulting from the need to report their own extensive fieldwork.) I’ve referred in passing to evidence that there has been a large-scale decline in density and ring width over hundreds of sites and it might be useful to do a quick survey of this evidence

  5. jimchip Says:

    Rutherford et al 2005 (the et al being half the Hockey Team: Mann, Bradley, Hughes, Briffa, Jones, Osborn) is a re-statement of the MBH98 network (flawed PCs and all) and the Briffa et al 2001 network using RegEM. I haven’t figured out exactly what the properties of the RegEM method are as compared to other multivariate methods, but that’s a story for another day. This is the article where they first put forward the idea that the verification r2 is a “flawed” statistic.

  6. jimchip Says:


    4) Whilst we are taking bets, proxies will never be better than
    instrumental data. Corals will eventually extend the SOI
    series but never be better than it for the years after 1850.
    Similarly with the NAO. Instrumental data exists to extend
    this to about 1750 and the fact that such data is sitting
    out there is only just begining to be realised. A great NAO
    reconstruction could be produced if the real data extended
    over nearly 200 years, enabling the low-frequency aspects
    to be considered in much more detail than ever before
    ( a la Stahle with the SOI).

    That’s enough for now.


    Subject: No Subject
    Date: Thu, 17 Sep 1998 10:35:12 -0400 (EDT)

  7. jimchip Says:


    >3) regarding proxies, I wonder how much of the “quality” issue regarding
    >ice cores and some other remote proxy records is due to there not being any
    >instrumental stations near them (and at the same altitude)? Also, with
    >respect to coral records, I get the feeling most in the coral community now
    >think there is something “funny” about long Galapagos record (age model,
    >maybe more – I think a new record is being generated). Also, many coral 18O
    >records (e.g., New Caledonia) are influenced by both temp and salinity
    >variations. This is a solid reason why the fit of such a record to temp
    >won’t be as good as you’d like (or as good as a buffo dendro record). I
    >think Terry Quinn is generating the trace metal data to sort temp out.
    >Lastly, I’ve now seen a number of coral records (most not published, but
    >Tarawa is an example I think) where the proxy does as well as local
    >instrumental data (in this case ppt) in getting the regional signal, AND
    >the local instrumental record only go back to the war. I’m guessing, just
    >between us, that ENSO recons based on proxies will soon be better than
    >instrumental ones before 1950 – not just before 1850! In fact, I’d bet on
    >it (using some of the money Ray still owes Julie!). Thus, I worry that it
    >might not be wise to dismiss reconstructions on a proxy basis, particularly
    >since trees lack one important trait – they don’t work for all parts of the
    >4) About trees…. (Keith are you still reading?? – I sent this to Ed and
    >Brian too, since they might have insights). Has anyone examined how a
    >tree-ring recon degrades as a function of sample size back in time. I
    >always see the quality of dendro recons cast as GREAT vs.other proxies (and
    >they are) based on comparison with instrumental records. But, the dendro
    >records usually have the best sample replication in this same instrumental
    >period, and then tail off back in time. For example, Brian’s Jasper recon
    >has a sample depth of ca 28 trees in the last century, but drops off to ca.
    >5 in the 12th century and 1 (?) in the 11th century. The “quality” of the
    >recon must degrade too?? In contrast, some non-dendro reconstructions may
    >not verify as well as dendro vs the instrumental record, but they might not
    >degrade with time either since the sample density doesn’t change with time.
    >Thus, could it be that at some point back in time, the dendro records
    >degrade to the same quality (or worse) than other proxies???

    From: Keith Briffa
    To: “Jonathan T. Overpeck” ,,,,,, Brian Luckman
    Subject: Re: climate of the last millennia…
    Date: Tue Oct 6 13:38:33 1998

  8. jimchip Says:


    As for decisions about the most appropriate baseline period to use for the
    series, that is as you point out an important issue and one we have to
    consider with some circumspection, especially if a “modern” calibration
    (e.g., 1931-1960) to the instrumental record gives a substantially
    different alignment
    from the more 19th century-oriented calibration you describe. The tradeoff
    of course is that the instrumental series itself is considerably less certain
    prior to the 20th century while, as you point out, the non-climatic influence
    on tree growth may be setting in by the mid 20th century. Something I think
    we can iron out satisfactorily at the next juncture.

    From: “Michael E. Mann”
    To: Tim Osborn ,
    Subject: Re: Briffa et al. series for IPCC figure
    Date: Tue, 05 Oct 1999 12:31:56 -0400
    Cc: k.briffa@uea, p.jones@uea,,

  9. jimchip Says:

    0966015630.txt Probably applies to 1.2, 3.2 (the usual suspects)

    Chris and John (and Mike for info),
    I’m basically reiterating Mike’s email. There seem to be two lots of
    suggestions doing the rounds. Both are basically groundless.

    1. Recent paleo doesn’t show warming.

    This basically stems back to Keith Briffa’s paper in Nature in 1998
    (Vol 391, pp678-682). In this it was shown that northern boreal forest
    conifers don’t pick up all the observed warming since about the late
    1950s. It was suggested that some other factor or a combination of
    factors related to human-induced pollution (e.g. nitrogen deposition,
    higher levels of CO2, ozone depletion etc). Hence in a new paper
    submitted to JGR recently we develop a new standardization approach
    (called age banding) and produce a large-scale reconstruction
    (calibrated over the period 1881-1960 against NH land north of 20N)
    back to 1402. If you want a copy of this can you email Keith and he’ll
    send copies once he’s back from holiday.

    This background is to illustrate how Singer et al distort things. The
    new reconstruction only runs to 1960 as did earlier ones based solely
    on tree-ring density. All the other long series (Mike’s, Tom Crowley’s
    and mine) include other proxy information (ice cores, corals,
    historical records, sediments and early instrumental records as well as
    tree-ring width data, which are only marginally affected). All these
    series end around 1980 or in the early 1980s. We don’t have paleo data
    for much of the last 20 years. It would require tremendous effort and
    resources to update a lot of the paleo series because they were collected
    during the 1970s/early 1980s.

    It is possible to add the instrumental series on from about 1980 (Mike
    sought of did this in his Nature article to say 1998 was the warmest of
    the millennium – and I did something similar in Rev. Geophys.) but there
    is no way Singer can say the proxy data doesn’t record the last 20 years
    of warming, as we don’t have enough of the proxy series after about 1980. takes the argument further
    saying that as trees don’t see all the warming since about 1960 the
    instrumental records recently must be in error (i.e. this group believes
    the trees and not the instrumental records). This piece by Idso and
    Idso seems to want to have the argument whichever suits them.

    From: Phil Jones

    To: “Michael E. Mann” , “Folland, Chris”
    Subject: Re: FW: Mann etal
    Date: Fri, 11 Aug 2000 13:40:30 +0100

  10. Jimchip Says:

    See also 1.9
    Briffa’s Avam-Taimyr Series

    Before continuing with Yamal, I’m going to make a little detour through the Avam-Taimyr series, the measurement data to which was also archived at the same time as the Yamal data. Taimyr, also originating in Briffa 2000, has been another staple of Team reconstructions in the past 10 years, but doesn’t have a HS pattern. Actually it had a noticeable Divergence Problem, with a 20th century peak in 1942.

    While Yamal stayed unchanged in Briffa et al 2008, the Taimyr series was modified noticeably, becoming the “Avam-Taimyr” series. To the previous Taimyr site (72N, 101E), Briffa added the Bol’shoi Avam site (70 30N 93E), about 8 degrees (!) to the west. One doesn’t expect Team adjustments to leave even small scraps on the table and this proved to be the case here as well – the added data substantially increased 20th century values and substantially lowered 1150-1250AD values, thereby altering the medieval-modern differential in favor of the 20th century.

  11. Jimchip Says:

    1061625894.txt Wigley and Wigley, T.M.L., Jones, P.D. and Briffa, K.R., 1987: Detecting the effects of acidic deposition and CO2-fertilization on tree growth.

    WRT the Idso paper. I think Phil got his “Empire strikes” idea from Timo:
    “We have already discussed about this study in July under title ?Empire
    Strikes back on Soon et al.? ´”

    From: “Michael E. Mann”
    To: Tom Wigley
    Subject: Re: [Fwd: VS: [Climate Sceptics] Mann & Jones on 1800 yrs proxies]
    Date: Sat, 23 Aug 2003 04:04:54 -0400
    Cc: Phil Jones , Gavin Schmidt , Michael Oppenheimer , Mike MacCracken , Tom Crowley ,,, Ellen Mosley-Thompson ,,, Keith Briffa , Kevin Trenberth , Tim Osborn , Gabi Hegerl , Stefan Rahmstorf ,, Eric Steig ,

    Thanks Tom,
    I agree–the issue is not completely settled, and thanks for the reference (any possibility
    you can send me a reprint?). The point here of course is that we are talking a potential
    effect, w/ as you say, at best a weak signal–hardly the dominating overprint that is
    argued by the Idso brothers! (by the way, weren’t they a circus act at one point??),
    At 12:48 PM 8/22/2003 -0600, Tom Wigley wrote:

    Thanks for your clarifications.
    With regard to the CO2 fertilization effect on tree ring width, I wrote a paper a number
    of years ago pointing out that there were signal-to-noise problems in identifying and
    quantifying such factors.
    Wigley, T.M.L., Jones, P.D. and Briffa, K.R., 1987: Detecting the effects of acidic
    deposition and CO2-fertilization on tree growth. (In) Methods of Dendrochronology.
    Vol. 1, Proceedings of the Task Force Meeting on Methodology of Dendrochronology:
    Kraków, Poland, 26 June 1986, (eds. L. Kairiukstis, Z. Bednarz and E. Feliksik),
    International Institute for Applied Systems Analysis, Agricultural Academy of Kraków,
    Polish Academy of Science, WOSI Wspólna Sprawa 38/37 no. 20, 239253.
    While I am confident that you are correct, and that this is not a crucial factor, I
    think one should be careful about denying its existence. There are, furthermore,
    additional obfuscating factors that make the effects of CO2 fertilization on ring widths
    hard to identify.
    Perhaps more important is the fact that many tree ring based reconstructions use density
    data, and the jury is still out on whether more CO2 increases or decreases density.
    Michael E. Mann wrote:

    Dear Colleagues,
    Several you have inquired about the below claims by the notorious “Idso brothers” which
    relates to the paper by Mann and Jones that appeared in GRL a couple weeks ago.
    Of course, its the usual disinformation we’ve come to expect from these folks, but a few
    details on why:
    1) The supposed “Co2 fertilization” argument is a ruse. The only evidence that such an
    effect might actually play some role in tree-growth trends has been found in high
    elevation sites in western North America (consult Malcolm Hughes for more details). As
    in Mann et al ’99 (GRL), any such effect, to the extent it might exist, has been removed
    from the relevant series used in the latest (Mann and Jones) paper through the removal
    of anomalous differences between low-elevation and high-elevation western North American
    temperature trends during the post 1800 period, prior to use of the data in climate
    2) We haven’t in the past extended the proxy reconstruction beyond 1980 because many of
    the proxy data drop out. However, the repeated claim by the contrarians that post-1980
    proxy data don’t show the warming evident in the instrumental record has finally
    prompted me to go ahead and perform an additional analysis in which the
    proxy-reconstruction is extended forward as recently as at all possible (to 1995, for
    which 3 out of 8 of the NH records are available, and 1 of the 5 SH records are
    available). The SH and GLB reconstructions are thus obviously tenuous at best, but they
    do address, to the extent at all possible, the issue as to whether or not the proxy
    reconstructions show the post-1980 warming–and they do.
    See the attached plot which compares the NH (blue), SH (green), and GLB (red) series
    through 1995. The late 20th century is the nominal maximum for all 3 series *without any
    consideration of the information in the instrumental mean series*. This thus refutes
    the 2nd criticism cited by the Idso brothers.
    One note about the 40 year smoothing. As in the trends in the instrumental series shown
    by Mann and Jones, a boundary constraint on the 40-year smooth has been used that
    minimizes the 2nd derivative at the boundary–this trends to preserve the trend near the
    end of the series and has been argued as the optimal constraint in the present of
    nonstationary behavior near the end of a time series (Park, 1992; Ghil et al, 2002). I
    favor the use of this constraint in the smoothing of records that exhibit a significant
    trend as one approaches the end of the available data. This might be worth talking about
    in the next IPCC when the subject of adopting uniform standards for smoothing data, etc.
    are discussed…
    In retrospect, Phil and I should have included this analysis in the GRL article, but its
    always hard to know what specifics the contrarians are going to target in their attacks.
    This analysis however, will be included in a review paper by Jones and Mann on “climate
    in past millennia” that is presently being finalized for “Reviews of Geophysics”.
    I hope that helps clarify any questions any of you might have had. Please feel free to
    pass this information along to anyone who might benefit from it.
    Now, back to fighting the “Shaviv and Veizer” propaganda along w/ Ben Santer and David
    Parker out in Italy…

    ——– Original Message ——–
    Subject: VS: [Climate Sceptics] Mann & Jones on 1800 yrs proxies
    Date: Wed, 20 Aug 2003 13:52:40 +0300
    From: Timo Hämeranta
    CC: “Charles F. \”Chick\” Keller” , “Kirill Ya.
    Kondratyev” , “Michael C. MacCracken”
    , “S. Fred Singer” , “Sallie
    Baliunas” , “Carl Wunsch” ,
    “David R. Legates” , “George Kukla”
    , “James E. Hansen” ,
    “Tom Wigley” , “Willie Soon”
    Dear all,
    GRL finally published the study
    Mann, Michael E. and Phil D. Jones, 2003. Global surface temperatures
    over the past two millennia, Geophysical Research Letters Vol. 30, No.
    15, 1820, 10.1029/2003GL017814, August 14, 2003
    [1] We present reconstructions of Northern and Southern Hemisphere
    mean surface temperature over the past two millennia based on
    high-resolution ?proxy? temperature data which retain millennial-scale
    variability. These reconstructions indicate that late 20th century
    warmth is unprecedented for at least roughly the past two millennia for
    the Northern Hemisphere. Conclusions for the Southern Hemisphere and
    global mean temperature are limited by the sparseness of available proxy
    data in the Southern Hemisphere at present.
    We already noticed the study in
    Mann, Michael, Caspar Ammann, Kevin Trenberth, Raymond Bradley, Keith
    Briffa, Philip Jones, Tim Osborn, Tom Crowley, Malcolm Hughes, Michael
    Oppenheimer, Jonathan Overpeck, Scott Rutherford, and Tom Wigley, 2003.
    On Past Temperatures and Anomalous Late-20th Century Warmth. Eos, Vol.
    84, No. 27, page 256, July 8, 2003
    There we found that ” …. an extension back through the past 2000
    years based on eight long reconstructions [Mann and Jones,2003].”
    CO2 Science Magazine today presents the study as follows:
    Was Late 20th Century Warming Really Unprecedented Over the Past Two
    Mann, M.E. and Jones, P.D. 2003. Global surface temperatures over the
    past two millennia. Geophysical Research Letters 30: 10.1029/2003GL017814.
    What was done
    Using 23 individual proxy records from 8 distinct regions in the
    Northern Hemisphere and 5 proxy records from the Southern Hemisphere,
    the authors constructed Northern and Southern Hemispheric and global
    mean temperature histories over the period AD 200 to as close as they
    could get to the present employing a 40-year lowpass filter of the data.
    What was learned
    Mann and Jones say their temperature reconstructions indicate that “late
    20th century warmth is unprecedented for at least roughly the past two
    millennia for the Northern Hemisphere.” They also say their data and
    analysis “suggest a similar, but less definitive conclusion, for the
    global mean.”
    Although we and many others have many bones to pick with many aspects of
    Mann and Jones’ analysis, we will here focus on just a couple of points
    and temporarily grant them the benefit of the doubt in those other areas.
    First of all, granting them almost everything they have done, it can
    readily be seen from their own graph of their own results that the end
    point of their reconstructed global mean temperature history is not the
    warmest period of the prior 1800 years. In fact, their treatment of the
    data depicts three earlier warmer periods: one just prior to AD 700, one
    just after AD 700 and one just prior to AD 1000 (see figure below).
    Reconstructed global temperature anomaly (based on 1961-1990
    instrumental reference period) adapted from Mann and Jones (2003).
    The globe only becomes warmer in the 20th century when its measured
    temperatures are substituted for its reconstructed temperatures. This
    approach is clearly unacceptable; it is like comparing apples and
    oranges. If one has only reconstructed temperatures from the distant
    past, one can only validly compare them with reconstructed temperatures
    from the recent past.
    Another important point that is ignored by Mann and Jones is that the
    last century witnessed a dramatic increase in atmospheric CO2
    concentration, which everyone knows is an effective aerial fertilizer.
    It also witnessed a dramatic increase in atmospheric nitrogen
    deposition, which further enhances plant growth. Consequently, as
    tree-ring data comprise the bulk of the proxy temperature information
    employed by Mann and Jones, their reconstructed global mean temperature
    history must possess a non-temperature-induced pseudo-warming signal
    driven by CO2- and nitrogen-induced increases in growth that make 20th
    century warming appear significantly greater than it really is. Hence,
    there could well be still other periods of the past 1800 years (in
    addition to the three we have already noted) when the global mean
    temperature was also warmer than it was at the end of their
    reconstructed record in the 20th century.
    What it means
    Mann and Jones have clearly failed to demonstrate the key point they
    desired to make in their paper. Their data, however, speak for
    themselves in clearly demonstrating that late 20th century warmth was
    not unprecedented over the past two millennia.
    We have already discussed about this study in July under title ?Empire
    Strikes back on Soon et al.? ´
    All the best
    Timo Hämeranta
    Moderator, Climatesceptics

    Professor Michael E. Mann

  12. Jimchip Says:

    World Dendro 2010 Divergence panel

    Mc was disinvited as a keynote speaker that Biffa was on.

    Date: Sat, 31 Oct 2009 13:17:25 +0000
    Reply-To: ITRDB Dendrochronology Forum
    Sender: ITRDB Dendrochronology Forum
    From: Tom Melvin
    Subject: Call for Papers on Divergence
    Content-Type: text/plain; charset=”iso-8859-1″; format=flowed

    We are trying to organise a session at the WorldDendro2010 in Rovaniemi (June 2010) The Divergence phenomenon in Dendroclimatology Convenors: Keith R. Briffa, Rosanne D’Arrigo, Kevin Anchukaitis and Thomas Melvin This session will review the current status and explore ongoing and potential future research focused on the “divergence” phenomenon in dendroclimatology. Though generally characterised as an observed divergence between the trends in tree growth series and in instrumental climate records during the last decades of the 20th century, different studies indicate a variety of geographical and temporal descriptions and suggest various explanations. The significance of the divergence phenomenon in the context of large-scale climate reconstruction is shown by the stress laid upon it in the Fourth Assessment Report of Working Group 1 of the IPCC, which states: “At this time there is no consensus on these issues…and the possibility of investigating these further is restricted by the lack of recent tree ring data at most of the sites from which the tree ring data…were acquired.” Contributions that describe specific regional or large-scale studies, focusing on recent research into the character, mechanisms, causes or implications of “divergence”are all welcome.

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