John Mitchell’s Review Comments

IPCC policies state that their process is supposed to be open and transparent and that all comments are to be archived. Previously, we observed that the Lead Author Responses to our Review Comments were completely unresponsive on key issues. Under IPCC policies, the Review Editor is charged with seeing that this doesn’t happen. John Mitchell of Hadley Center was Review Editor of chapter 6. Despite policies to the contrary, the IPCC refused to provide complete comments by Mitchell and other Review Editors, providing only their sing-off statements.

David Holland attempted to obtain Mitchell’s review. These were refused on a variety of pretexts: first, that they had been destroyed; when that didn’t work, on the grounds that Mitchell had acted in a “personal” capacity; when that didn’t work (due to the fact that David Holland requested FOI information on who paid for his travel to IPCC meetings, they adopted the strategy referred to by Phil Jones – that IPCC was an international organization and that responding to FOI would interfere with UK relations with an international organization.

Ross McKitrick wrote me reporting that Mitchell made some on-point comments about the Hockey Stick issue. Mitchell’s comments could have been made by a CA reader. For example:

Is the PCA approach robust? Are the results statistically significant? It seems to me that in the case of MBH the answer in each is no

There’s more.

From John Mitchell to Jansen and Overpeck

I am in Geneva at the WMO EC meeting,so I have not had a lot of time to look at the SOD comments. I can not get to Bergen before Tuesday. I had a quick look at the comments on the hockey stick and include below the questions I think need to be addressed which I hope will help the discussions. I do tbelieve we need a clear answer to the skeptics . I have also copied these comments to Jean. Please let me know that you have received this, and what email address I can contact you at in Bergen¨.
With best wishes

1. There needs to be a clear statement of why the instrumental and proxy data are shown on the same graph. The issue of why we dont show the proxy data for the last few decades ( they dont show continued warming) but assume that they are valid for early warm periods needs to be explained.

2 . There are number of methodological issues which need a clear response. There are two aspects to this. First , in relation to the TAR and MBA which seems to be the obsession of certain reviewers. Secondly (and this I believe this is the main priority for us) in relation to conclusions we make in the chapter We should make it clear where
our comments apply to only MBH (if that is appropriate) , and where they apply to the overall findings of the chapter. Our response should consider all the issues for both MBH and the overall chapter conclusions
a. The role of bristlecone pine data: Is it reliable? Is it necessary to include this data to arrive at the conclusion that recent warmth is unprecedented?
b. Is the PCA approach robust? Are the results statistically significant? It seems to me that in the case of MBH the answer in each is no. It is not clear how robust and significant the more recent approaches are.
3. The chapter notes that new data has been included, but we dont say how much or is this is substantial or minor. The impression I have that the amount added is minor, but I cant tell.
4. The Esper et al and Moburg et al data both show increased variance, but the temporal patterns are quite different. We need to say why the discrepancy does not undermine our conclusions of greater cooling in the Little Ice Age.
5. I have not had time to check the original chapter, but the comments give the impression that the recent 50 yr warming is unprecedented over the last 500years (seems reasonable) and elsewhere over the last 1000years (less clear)

John FB Mitchell


  1. HR
    Posted Nov 23, 2009 at 10:07 AM | Permalink

    Have you asked for their definition of open and transparent?

    • jlc
      Posted Nov 24, 2009 at 5:44 AM | Permalink

      Have you asked for their definition of “robust”?

  2. Posted Nov 23, 2009 at 10:24 AM | Permalink

    Well that email shows that they were questioning, yet sought to conceal these quite obvious questions. The common accusation is that ideology is clouding their judgement, this post supports that accusation.

  3. Posted Nov 23, 2009 at 10:30 AM | Permalink

    Good grief, is there anything that they haven’t tried to fix?

  4. Alan Hohn
    Posted Nov 23, 2009 at 10:57 AM | Permalink

    1. There needs to be a clear statement of why the instrumental and proxy data are shown on the same graph. The issue of why we dont show the proxy data for the last few decades ( they dont show continued warming) but assume that they are valid for early warm periods needs to be explained.

    Yes! This one jumped out at me right away. The divergence problem is important. In our discussion of whether “hide the decline” is an infelicitous phrase, it must not be forgotten that the reason the decline had to be hidden, adjusted, or otherwise ‘transitive-verbed’ is that this divergence really exists for some important proxies.

    It is insufficient to hand-wave this problem with discussions of modern secondary effects like precipitation patterns without a defensible quantitative method of eliminating these effects and showing that the resulting proxy data does correlate with modern temperature. Also nice would be a way of detecting those secondary effects without reference to the divergence itself, since otherwise how do we know what parts of our historical data are similarly tainted?

    This gets back to the essential issue which the Team still hasn’t comprehended, as evidenced by their repeated complaints in the e-mails that Mr. McIntyre hasn’t produced his own temperature reconstruction. The burden of proof is fully on the people who assert the validity of the proxy-based reconstructions, especially if these reconstructions are to be used as the basis of policy. (Certainly there are those who argue that policy cannot ‘wait’ for the science, but even if they are correct, that’s a political argument, not a scientific argument, and it’s inconsistent to say on the one hand that you have science on your side, and on the other hand that you’re pursuing policies in advance of what the science demonstrates.)

  5. Ross McKitrick
    Posted Nov 23, 2009 at 11:42 AM | Permalink

    Here are some of my review comments on Ch 6, that I think JFB Mitchell was referring to. Bear in mind that the final version of the chapter did not in any way reflect the points Mitchell raised in his email.

    Fig 6.10. I here repeat a point made in my comments on the FOD. It is statistically invalid and visually misleading to overlay the black instrumental line on this diagram. The coloured graph lines show proxy records that end at 1980. If you want a line that continues up to more recent years that then you must use the proxy records that continue past 1980, not switch to a different type of series. There are up to date proxy records available, but as I’m sure the authors of this chapter are aware, they depart from the surface instrumental record, many of them declining after 1980. By failing to show this, and including the surface temperature data in black, it constitutes a misrepresentation, since the black line is an invalid forward extrapolation of the proxy data. If the reason for not showing the updated proxies is that they are not considered to be good representatives of temperature anymore, then by what right does the Figure insinuate that they were good proxies 8-10 centuries ago? It is no defence to claim that MBH99 established a statistically skillful relationship between the proxy network and the instrumental data, since that claim has been refuted, as discussed above. McIntyre and McKitrick (2005a,d) showed that the pre-1450 RE statistic was incorrectly benchmarked, yielding a spurious inference, and the r2 stat calculated by MB&H themselves, which showed the lack of skill, was simply not reported. The failure of the r2 and CE stats is confirmed by Wahl and Ammann. The squared correlation between the MBH long proxies and the instrumental record is nearly zero (MM05a,c). The mean correlation between the long NOAMER proxies and gridcell temperatures in the MBH98 data set (which dominate the pre-AD1450 portion) is -0.08 (McIntyre and McKitrick 2005c), and the RE significance benchmark is above the MBH98 RE score, using all available implementation of the Mann code (McIntyre and McKitrick 2005d). The surface instrumental record cannot be used as a statistically valid extrapolation for the proxies after 1980.

  6. Posted Nov 23, 2009 at 11:59 AM | Permalink

    Process is kicking in:

    This organisation have lodged a complaint to the UK’s Information Commissioner 😀

  7. O. Weinzierl
    Posted Nov 23, 2009 at 12:04 PM | Permalink

    Hans von Storch writes on

    “Another conclusion could be that scientists like Mike Mann, Phil Jones and others should no longer participate in the peer-review process or assessment activities like IPCC.”

    I think lots of people feel like this!

  8. Posted Nov 23, 2009 at 1:20 PM | Permalink

    This sums up the situation with those wishing to express an opinion on the BBC’s website about Climategate – almost a week in.

    “8. At 4:29pm on 23 Nov 2009, Andydaws wrote:
    OK, where do we start…Of course, we’ll write this with the Moderators in mind.

    First, Paul, congratulations on having correctly called the “state of play” on the temperature trend of the last decade (actually, on a linear model, we have to extend to 1997 to get a trend of more that 0.35C/century – versus a 95% confidence interval of +/- 1.2C.) Despite a good deal of obfuscation and criticism when you first posted, that conclusion seems pretty well acknowledged – ALLEGEDLY.

    Second, re authenticity – as far as I can tell, none of the ALLEGED protagonists are claiming the ALLEGED material is anything other than completely authentic.

    Third, there looks to be a VERY good chance that there’s no hacking involved. On his “Climate Audit” website, Steve McIntyre, the “bete noir” of the CRU points out he’d just received yet another refusal for the release of data dated on about the date that the file found it’s way onto the Russian site; that the file is ALLEGEDLY dated a day or two before the letter turning him down. Also, the file’s ALLEGEDLY titled “foi2009”, and that it’s ALLEGED metadata shows is consistent with that ALLEGED creation date and ALLEGED title.

    Which rather suggests an internal leak, not a hack at all. Not that your colleagues Black & Harrabin appear to have so much as considered that possibility.

    Fourth, the more recent developments from the ALLEGED analysis of the ALLEGED material are now focussing not on the ALLEGED e-mails, but on the ALLEGED fortran code, and an ALLEGED “read me” programmers file. Apparently and ALLEGEDLY there’s a chap called “Harry” who could possibly be undergoing a very uncomfortable ALLEGED time. ALLEGEDLY the ALLEGED “READ ME” makes very clear just how extreme the ALLEGED measures taken to ALLEGEDLY ensure that the paleoclimate studies produced the ALLEGEDLY desired “hockey stick” shape. Further the ALLEGED file ALLEGEDLY shows that the basic data set is ALLEGEDLY corrupted beyond all recognition, due to ALLEGEDLY poor data management practices.

    The ALLEGEDLY significant issue with the ALLEGED “hockey stick” treatment is that the code is ALLEGEDLY designed to ALLEGEDLY overwrite all treering proxy data after 1960, because it ALLEGEDLY shows poor ALLEGED agreement with instrumental temperature records, but ALLEGEDLY treats the tree-rings as a reliable proxy for temperature before 1960. That’s ALLEGEDLY very questionable practice…….

    Some of the other ALLEGED issues raised by the ALLEGED documents ALLEGEDLY include

    ALLEGED efforts to get sceptical academics removed from post.
    ALLEGED efforts to stop critical journals getting published
    ALLEGED admissions that there is a static/cooling trend that ALLEGEDLY can’t be explained by the current models – amusingly, that’s ALLEGEDLY a problem with the data, not the models….ALLEGEDLY, it’s a travesty!
    ALLEGED breaches of Freedom of Information legislation.
    ALLEGED attempts to get another BBC journalist to bring Paul to task for writing the “whatever happened to Global Warming” piece…
    ALLEGED discussions about changing the Sea Surface temperature record to make an unfortunate warm even in the 1940s go away.

    Amidst other stuff…..”

  9. chainpin
    Posted Nov 23, 2009 at 1:26 PM | Permalink

    Indeed Alan, that is why the divergence issue was listed as the number #1 concern by Mitchell–problem is they couln’t explain it then and they can’t explain it now.

    If you can’t fix the divergence problem, then you cannot defend the model–and out the window goes the theory.

    There is another email where Briffa goes into detail about the divergence problem, but I can’t find it.

    The depths of The Team’s blatant lack of respect for the sanctity of the scientific method is disgusting.

    Welcome to the new era of Big Science.

  10. Posted Nov 23, 2009 at 1:35 PM | Permalink


    “At 5:57pm on 23 Nov 2009, kh1234567890 wrote:
    “I was forwarded the chain of e-mails on the 12th October”

    And you just sat on it for a month, hoping that it will go away ?”

    Sounds very much like the BBC were going LALALANOTLISTENING a month ago FFS.

    No wonder the leaker resorted to going off-piste – thankfully they did or we’d be a hostage to the BBC’s agenda.

  11. Barclay E. MacDonald
    Posted Nov 23, 2009 at 2:04 PM | Permalink

    It should be noted that the second paragraph above regarding David Hollands efforts to obtain information were concurrently discussed on at CA and some of the alleged emails that partially corroborate this are discussed here: The thread is entitled When in Doubt Delete.

  12. Arthur
    Posted Nov 23, 2009 at 2:06 PM | Permalink

    I like the privileged elitism: they can question the evidence for global warming among themselves, but the rest of us are not allowed to, and must expect to be attacked if we do.


  13. AKD
    Posted Nov 23, 2009 at 2:39 PM | Permalink

    Re: Paul Hudson.

    I strongly suspect someone forwarded some part of the string of e-mails that begins on October 12 and ends on October 14 with 1255318331.txt, as they are about Paul Hudson. I think he is saying the string of e-mails he received matches up with some of the e-mails contained in the leaked folder. It would have been possible for him to have received this exact package of material then as there is content dated after October 12.

    Interesting nonetheless that someone who received these e-mails though Hudson should see them….

    First e-mail header:

    From: Stephen H Schneider
    To: Myles Allen , peter stott , “Philip D. Jones” , Benjamin Santer , Tom Wigley , Thomas R Karl , Gavin Schmidt , James Hansen , trenbert , Michael Mann , Michael Oppenheimer
    Subject: Fwd: BBC U-turn on climate
    Date: Sun, 11 Oct 2009 23:32:11 -0700 (PDT)

  14. AKD
    Posted Nov 23, 2009 at 2:39 PM | Permalink

    make that *impossible*

  15. Shona
    Posted Nov 23, 2009 at 2:51 PM | Permalink

    Hello Steve,

    As a newbie to this may I thank you you the amazing, thankless work you have put in on this? I think there should be a “Galileo” prize, and you be its first recipient.

    My question, I understand that Seier, who is mentioned as needing to be got rid of was indeed got rid of. Do you know what happened with that? Is it known why he left his post?

  16. eric
    Posted Nov 24, 2009 at 4:54 PM | Permalink


    The work SM has done (with others like Ross, Jeff, Jean, Roman, Lucia etc) is not entirely thankless. There are those of us who are very thankful!!

    but I agree, they should get some sort of prize for “rigorous, relentless, and insightful auditing under fire in service of the public interest”.

    Unfortunately somehow I do not think that they will be on the Nobel committee’s shortlist.

    Until then – make sure to hit the tip jar! I am going there now myself.

  17. Posted Nov 24, 2009 at 5:34 PM | Permalink

    I’m not sure if this has been noted in another thread, and apologies if it has, but there is some ongoing work on the temperature dataset here. So far, it seems to be showing that temperatures in the 20th century may have been exaggerated.

  18. Craig Loehle
    Posted Nov 24, 2009 at 8:39 PM | Permalink

    Mitchell raises many valid points but not so much to get at the truth but seemingly to make sure they can make their claim of “unprecedentedness” in safety. If the data is shaky, don’t make such a claim.

  19. Posted Nov 24, 2009 at 8:40 PM | Permalink

    paulhan: spot on! I would love to see a whole new Thread here on the integrity or lack of it of the global surface temperature sets since 1850 (CRU) and 1880 (NOAA). EM Smith (htttp:// been documenting how especially since 1998 the approved met temp stations have been marching south in the NH and north in South America and Australia, and everywhere going down hill from the mountains to the beaches (e.g. the Andes’ stations have been abolished by NOAA and GCHN). How far if at all do CRU and NOAA weight their annual “global” temperatures for the constantly changing latitudinal distribution of the instrumental records?

    The further issue I would like to see taken up is the utter lack of correlation between changes in atmospheric CO2 as measured at Mauna Loa (since 1958) or Pt Barrow and changes in temperature at ANY SPECIFIC location – the CRU/Gistemp global sets are worthless becuase of the constant Jones-Hansen fiddles. I have done some 50 stations in Hawaii, California, Alask, Australia, and UK, and have yet to find a single place where the R2 is much if any better than the 0.00 of the MBH hockeysticks, with not a single significant t-statistic on the dCO2 coefficient.

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