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Scientist Sets Record Straight on Medieval Warming Research

Posted on 31 March 2012 by greenman3610

This is a re-post from Climate Crocks regarding the myth that the Medieval Warm Period was warmer than present. 

daily fail

Yesterday I reported that the newest bogus climate denial meme rocketing around the Foxis of Evil had been disavowed by Geochemist Zunli Lu. At first all I had was a short message indicating that the Daily Mail Newspaper, and reporter Ted Thornhill had deliberately decided to publish a piece that Dr. Lu told them contained the wrong ‘angle”.

Now we have Dr. Lu’s more complete statement.

Syracuse University:

Recently published climate research by Zunli Lu, a geochemist in the Department of Earth Sciences in Syracuse University’s College of Arts and Sciences, has gone viral across the Internet by bloggers. A number of media outlets, including theDaily Mail and The Register, which are published in the United Kingdom, claim this research supports arguments that human-induced global warming is a myth. The claims, Lu says, misrepresent his work and the conclusions in the study. The statement below is an effort to set the record straight. The original news story about the research is posted on Arts and Sciences News.

Zunli Lu:
“It is unfortunate that my research, “An ikaite record of late Holocene climate at the Antarctic Peninsula,” recently published in Earth and Planetary Science Letters, has been misrepresented by a number of media outlets.

Several of these media articles assert that our study claims the entire Earth heated up during medieval times without human CO2
emissions.  We clearly state in our paper that we studied one site at the Antarctic Peninsula. The results should not be extrapolated to make assumptions about climate conditions across the entire globe. Other statements, such as the study “throws doubt on orthodoxies around global warming,” completely misrepresent our conclusions. Our study does not question the well-established anthropogenic warming trend.”

Fake Science, Deliberate Distortions for Tea Party Yokels

In one of the clearest demonstrations in memory of the gullible and credulous nature of the the pathetic yokels that frequent such sites as Wattsupwiththat and Climatedepot, this obviously distorted meme was picked up and broadcast uncritically (remarkable, considering the source) around the world.

For more contextual information, see my post of yesterday.

If you are going to write about fiendishly difficult and involved matters of science and technology, it is not necessary to be an actual scientist, although that helps.  What IS necessary is to scrupulously refer back to real science, real scientists, and primary sources. I’ve built the reputation of this blog and  this video series on that premise, and that is my commitment to my readers.

Climate Crocks eviscerated a similarly bogus meme some time ago in a video entitled “Birth of a Climate Crock”. Watch that and compare to see how the technique works, and who the players are.

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Comments 1 to 50 out of 55:

  1. Dr. Lu should contact Mr. Anthony Watts and ask him to please correct the glaring error on WUWT. Mr. Anthony Watts, proudly declared that this paper was vindication of his long held belief that the Medieval climate anomaly was global.

    Mr. Anthony Watts:
    "Yes, I know, I covered it first: The Medieval Warm Period was Global"

    Will Mr. Watts, in the interest of scientific integrity and robustness, correct the error? Dr. Pielke Senior maintains that "I have worked with Anthony and he is devoted to the highest level of scientific robustness", if that is true, Mr. Watts will respect Dr. Lu's wishes and correct the record, and refrain in the future from perpetuating scientifc myths.
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  2. Albatross:

    Perhaps you should take Dr Roger Pielke Sr.'s statement about Anthony Watts with a grain of salt?

    They are, after all, bossom buddies pursuing a common agenda.
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  3. John Hartz:

    How do you know Albatross isn't, in a deadpan manner, taking the accuracy of Pielke Sr's statements with a grain of salt (or two)?
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  4. John H. and Composer,

    Actually, see no reason not to doubt the sincerity of Pielke senior's statement and do not doubt that he meat to say exactly what did.

    What is very unfortunate is that Pielke senior's position on this particular issue/matter is clearly horribly wrong (as evidenced by pretty much every blog post made at WUWT, inlcuding the one misrepresenting Dr. Lu's findigs), but that Roger cannot bring himself to admit it.
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  5. The author, Zunli Lu, deserves a pat on the back for quickly responding to the misrepresentations of his paper. We don't see that often enough.
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  6. Albatross:

    I see no reason why Pielke Sr cannot be sincere as you suggest, so I will retract my interpretation of your comment.

    That said, it does not follow from "Pielke Sr's assessment of Watts' devotion to scientific robustness is sincere" that "Pielke Sr's assessment of Watts' devotion to scientific robustness is correct", which is what I presumed was the humourous subtext you were trying to convey.

    =====

    With regards to the Lu et al 2012 paper, the commentariat at WUWT appears to support the notion that the paper says what they think it says, not what the paper's author(s) report it says. Commenter bill at Deltoid shares some examples there.
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  7. I have already endeavoured to take this up with Watts, and have been labelled an 'anonymous coward' for my pains (I have a rather old WordPress profile that kicks in wherever I browse a WP blog, much as many of his regulars appear to).

    I was also lambasted for having 'green' in my email address, a clear indicator of bad intent, it seems.

    (For the record I used to run a business called 'Green Heritage' supplying local-native seeds to state and local government.)

    I kid you not.

    You'd almost think I hit a nerve.

    He's neither retracting nor revising, and he will not be publishing Zunli Lu's response in either of the articles he's devoted to the issue, including the one that celebrates his own success in inaugurating the 'this paper proves the MWP was global and is yet another disproof of AGW' meme:

    REPLY: I’m not discomfited, but quite amused. The headline is accurate and stays. Syracuse is well aware and was within minutes, and has no issues with it. Again, with my sincere blessings, be as upset as you wish. – Anthony
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  8. Bill: Courageous, but pointless. First rule of denial is never admit an error.

    However, this episode should be documented and word of it shouted from rooftops. The author says they have it wrong and they don't care one bit. If this is what passes for credibility in the denial-o-rama, who can believe a word they say?
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  9. With respect, and with the caveat that I have not read any comments on either WUWT thread, Anthony Watts has nothing to apologize for with regard to this paper.

    His first post, linked by Albatross @1 above, merely asserts that the paper is evidence the MWP was global. That is true, and massively over interpreted by readers both here and (I am certain) at WUWT. X being evidence for Y is a very weak epistemic relationship. It is true whenever it is the case that the probability of Y given that X is greater than the probability of Y given that it is not true that X.

    The paradox of the ravens demonstrates how weak the "is evidence of" relationship is. Briefly, the statement that

    a) All ravens are black;

    is logically equivalent to the statement that

    b) Everything which is not black is not a raven.

    It follows that any fact such that, given that fact it is more probable that everything which is not black is not a raven also makes it more probable that all ravens are black. Ergo, discovery of a red apple is evidence that all ravens are black, as paradoxical as that may seem.

    It seems paradoxical only because humans have the habit of interpreting "X is evidence that Y" to mean that "X is conclusive evidence that Y", or at a minimum that "X is very substantial evidence that Y". Most people would endorse the claim (I suspect) that if X is evidence that Y, then given X, prima facie Y. However, the real world is far more complex that. It contains evidence for many statements which are in fact false. Indeed, science is built on the notion that evidence Y does not close the case.

    Now, I suspect that Watts takes the view that the Lu study "is another nail in the coffin" of the view that the MWP was not global. But evidence exists that it was not:



    Consequently there is substantial doubt that the coffin for the view that the MWP was not global will ever be built, let alone have the lid nailed down. But that in no way precludes some facts taken in isolation making it more probable than not that the MWP was global.

    Watt's second post is even less objectionable than the first, containing as it does just the full text of the press release from Syracuse University plus some quotes from the paper.

    The issue here is not whether Watts should correct the errors in his coverage of this issue for it is not evident that he has made any. Rather, the issue as this relates to Watts is will he, or will he not include the latest statement from Syracuse University as an update to his post to avoid over interpretation of the data? That he do so is a reasonable request. Should he not do so upon request, that would be reasonable grounds for criticism. It would be evidence of bias in his coverage of the issue, and evidence that he is quite happy that the paper be over interpreted.

    However, whether he does or not, that does not justify our over interpreting his posts as has been done in this thread.
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  10. Update: Watts has now included an update in which he defends his interpretation, but says:

    "Some media (The Daily Mail for example) have oversold the conclusions of the paper, and thus this is why the authors have issued a statement. Based on their words above in their own paper, I stand by my headline. Note that the authors at Syracuse have NOT asked me to change my headline nor any part of my post on the issue."


    I believe the authors statement deserves more prominence than a simple link. I also believe the section of the paper from which Watts quotes is poorly worded, implying as it does that all points between Europe and the West Antarctic Peninsula were warm during the MWP, which goes well beyond the evidence in the paper. (I do not think it was what the authors intended to imply, but was, as I say, a poor choice of words.)
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  11. Tom,
    Watts' 2nd post takes the immediate approach of suggesting pressure on SU researchers, postulating some 'Mike Mann's gospel.' This is more of the same old-same old. There are no over interpretations of his post here -Watts' words speak for themselves.

    The SU statement, '"completely misrepresent our conclusions," is ample justification of comments here.
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  12. Which was the point I was making all along.

    Watts clearly was celebrating inaugurating this very meme in his second post on the subject,

    'Yes, I know, I covered it first: The Medieval Warm Period was Global'


    And, technical defensibility of his original headline notwithstanding, this was clearly the place for him to point out that the lead author disagreed with this very assertion - to whit, that based on his paper anyone could simply assert 'the medieval warm period was global' particularly given that he was well aware of the advance of this meme, if only by the contents of the comments posted on his own blog!

    To my mind Watts simply could not credibly maintain bystander status in the propagation of this meme.

    And I note that he has not rescinded the headline above.

    I note also that this apology begins

    Since a number of commenters that are getting bent out of shape over the issue can’t apparently be bothered to read the paper, and since the authors at Syracuse themselves are under pressure because the alarmosphere has gone ballistic over the possibility that Mike Mann’s “there is no MWP much less global” gospel might be challenged, I offer readers this passage from the actual paper: [my emphasis]


    I had ready put to him that authors will have to fireproof the wording of their conclusions from agenda-based constructions, and pointed out that university PR staff are not the people to confirm whether a particular construction is a fair interpretation of a paper's conclusions, particularly as opposed to the authors themselves, as anyone whose large workplace has a PR department will doubtlessly be aware.

    He does not offer Zunli Lu's statement on the matter in the body of his own article/s, which is what I challenged him that he had a clear obligation to present. He still only offers a link to it, and I find it very difficult to credit that he would not have been perfectly content to ignore it entirely had not the issue been repeatedly raised.

    Now he has acknowledged that the very Daily Mail article he originally linked to without qualification is an over-interpretation, and he certainly deserves credit for doing so.

    May I remind you what he headline in question at the Daily Mail was?

    Is this finally proof we're NOT causing global warming? The whole of the Earth heated up in medieval times without human CO2 emissions, says new study


    I believe I played some part in this matter of the record-correcting updates in the body of his pieces, and am pleased to have done so

    Further, I will point out that this is a result, in that the folks at WUWT must acknowledge they cannot credit the Daily Mail's absurd spin on the tale

    I'll further suggest that such results is what this is about - and, to my mind, constraining blatant 'dog-whistling', such as is exhibited in the original second article.
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  13. This sort of thing is most disturbing. Not only does the good doctor have to explain the meaning of his paper, he now must refute, word for word, those that willfully misrepresent him. I did that myself, because whatever I typed in that space would have gotten snipped anyway.

    I worry that this is going to serve to intimidate people who would otherwise produce meaningful research because it's just not worth the hassle.
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  14. In essence, Watts' work is done on this issue. The echo chamber has already picked up the meme and it is spinning out of control. If you search 'ikaite,' a mineral few had heard of before this, you even find a repeater who claims ikaite is a vegetable.

    Watts knows that once he gets a story going, his sycophants will happily create so much noise that any fine details will be drowned out. Here, the poor author is saying 'that's not what the research shows!' Nobody (except a few of us) is listening.
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  15. muoncounter @11, I noticed the boilerplate about "Mann's gospel" which is typical of Watts and why (among other reasons) I do not consider him in anyway a reliable source on science. Regardless of of what we think of him, however, it is important to criticize what he actually says, not what we expect he would say. On that basis, the criticisms of Watts in this thread are unfair.

    We can contrast the coverage of this issue by Watts and by the Daily Mail. The lead headline by the Daily Mail for this story reads:

    "Is this finally proof we're NOT causing global warming? The whole of the Earth heated up in medieval times without human CO2 emissions, says new study
    Evidence was found in a rare mineral that records global temperatures
    Warming was far-reaching and NOT limited to Europe
    Throws doubt on orthodoxies around 'global warming'"


    This headline, and the the article that follow it completely misrepresent the paper and deserve harsh criticism. More importantly, it is clearly the target of the Syracuse and Lu rebuttal. In particular, Lu quotes from this headline when he says:

    "Other statements, such as the study “throws doubt on orthodoxies around global warming,” completely misrepresent our conclusions."


    Hence it is the Daily Mail article in particular, and other similar articles in the mainstream media which are the subject of criticism by Syracuse and Lu. Indeed, Lu himself may not even be aware of Watts.

    In contrast, Watt's claims have been quite circumspect. The essential claim is that the paper is "More evidence the Medieval Warm Period was global", which is a reasonable gloss of the claim made in the paper that, "...our ikaite record builds the case that the oscillations of the MWP and LIA are global in their extent...". If that claim is treated as meaning that the data in the paper establishes a prima facie case that the MWP was global in extent, it is false. If it is treated as claiming that it overwhelms the counter evidence, it is also false. But if it is understood as making it more probable that the MWP was global than the opposite finding at that site would have done, then it is true.

    I think Watts is subject to legitimate, and harsh criticism on many grounds. I think he can be criticized even in this episode in that he linked to the Daily Mail article without stating the obvious that it radically misrepresented the contents of the paper. I think also that he would do better to publish the full clarification from the University of Syracuse rather than just a link. But the criticism of Watts in the first few posts on this thread is unjustified and based on an over interpretation of his claims.
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  16. 'Yes, I know, I covered it first: The Medieval Warm Period was Global'

    [Link to the Daily Mail's absurd article: Watts - 'I must have had 20 tips... like this one']

    ...WUWT had the story first, 5 days ago on March 22nd. Somehow a lot of people missed it, so I’m linking to it again. Read it here: More evidence the Medieval Warm Period was global

    And I have more graphs and information from the actual paper than the Daily Mail has.


    This latter is certainly true. Too bad the Daily Mail's piece is hyperbolic BS, but this was apparently not worth mentioning at the time of posting.

    While I appreciate your position, Tom, I do feel you're being rather kinder than I'm inclined to be.

    As muoncounter says @ 14, the damage on this one is done with little chance of any meaningful correction of the record in the public mind. Celebrations of the propagation of such a misleading meme seriously irk me.
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  17. bill @16, it is not a question of being kind to Watts, something I am scarcely likely to be accused of. It is a question of being accurate.

    Beyond that (though less important IMO), it is a missed opportunity. Had the initial challenge to Watts been why he had not notified his readers of the misrepresentation by the Mail, he may have responded by defending the Mail's coverage. Certainly his readers would have. In either case, they would now be facing the situation in which your challenge was vindicated by the lead author himself.

    Had Watts himself supported the Mail Online's claims, he would have no refuge to hide in. He himself would have been caught clearly misrepresenting the science. Had his readers defended the Mail's coverage, then Watt's would have no excuse for not correcting the record when he first published the link. In particular any claim that his readers are sufficiently well informed to not be deceived by the Mail would be refuted by their defense of the article.
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  18. What I don't understand in discussions about eg. the MWP is, that even if it was global, why that supposedly disproves AGW today? Just because something similar to today happened in the past, doesn't mean that it happened for the same reasons, does it? This is like the analogy with bushfires which were started due to eg. lightning strikes before humans appeared so today's fires could not have been started by arson.
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  19. Good point, Baerbel. The current situation is somewhat unique in the history of Planet Earth!
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  20. [inflamatory snipped]

    The reason the MWP makes a difference to them is that they have their own imaginary version of what AGW theory is that bears no correspondence to reality. So in the case of MWP, their basic idea is that if the earth warmed and cooled within historic times, we 1) can't figure out why and 2) can't tell any difference between then and now. Magical denial. Scientific evidence that the MWP was just heat being redistributed around the globe doesn't fit their worldview. Their worldview is more about identity politics than even ideology these days.

    But to John's point in 19...the MWP is about the rhetorical point of denying the current situation is unique. Only temperature matters, causes are irrelevent. "Natural Cycles" don't require explanation.

    For my part I'd like to see a supplement on the MWP that offered explanations of what was going on then...shift in current patterns etc...why they shifted, why they shifted back etc.

    And in my view Mann's 2009 paper as cited Tom Curtis is brilliant piece of work...making clear the differences between then and now. Just don't expect a denier to give it any credence- because Mike Mann is an author it's tainted.

    Some points on arguing the 2009 paper... all the data and methods are archived with Science and freely available. So much for the memes of hidden data and methods. However you do get people stuck in a 1998 timewarp. Does anyone know if the self-appointed climate auditors have done anything with Mann 2009 or BEST? Or is the silence deafening?
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    Moderator Response: [Dikran Marsupial] Inflamatory material snipped. Please can we stick strictly to the scientific issues and avoid inflamatory or partisan comments.
  21. My understanding is that ice age/interglacial cycles are triggered by globally averaged climate forcing of no more than a quarter of a Watt. Presumably then, the relatively small global warming and cooling trends of the last millennium (probably less than 1C from max to min) must have been the result of even smaller forcings. Today's anthropogenic forcing is already much greater - about 1.7 Watts net forcing since 1750 - and so can be expected to produce much larger climate changes if we carry on with anything like 'business as usual'. So the 'MWP', far from reassuring us that there is No Problem, should be taken as a clear indication that we're conducting a very dangerous experiment with the Earth's climate.
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  22. Icarus @21, the globally averaged Milankovich forcing of only about 0.25 W/m^2 as you say, but that is only because the geographical configuration of the Earth made it extremely sensitive to very large regional and seasonal forcings associated with the Mikankovich cycle. Specifically, the greater sensitivity to summer forcing, and the existence of continents in the NH between 30 and 60 degrees North, but ocean in the SH between 30 and 60 degrees South meant high or low summer NH insolation can trigger very large albedo feedbacks. Consequently it is not possible to determine climate sensitivity from the very low globally averaged Milankovich forcings which trigger glacials or interglacials.

    It is, however, possible to treat the slow feedbacks of the transition between glacial states as forcings, and determine the climate sensitivity of the fast feedback response. That turns out to be approximately 0.75 degrees C per watt meter squared of forcing, or 2.8 degrees C per doubling of CO2. Of course, that is the fast feedback only. The climate sensitivity including slow feedbacks may be up to double that, and will certainly be larger.

    What the extremely sensitive balance of the glacial/interglacial transition does tell us is that the assumption that we can warm the Earth by 2 to 4 degrees C and be sure of a predictable response is nonsense. We may be lucky, or we may pass another transition which adds on another 2 to 3 degrees of warming rapidly. As Richard Alley says, we know that those transitions are out there. We just don't know whether we will pass one of them with 1, 2, 3, or even 4 degrees of warming.
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  23. Those on the science side of this discussion understand the importance of the points raised immediately above. Just as those on the science side will look to the Lu etal paper before trumpeting any conclusions. Note that these presumptive conclusions appear to be based on what the abstract calls 'qualitative.'

    However, Watts and his fellow travelers ignore these points and invent the fabrication that SU hasn't asked that the story be withdrawn. Look at the SU statement: on their letterhead, under the same name as the initial release, the meaning could not be more clear.

    We're in a situation analogous to the flap over Kirkby's initial CLOUD results. He simply did not say what the W gang heard, but that didn't slow them down.

    [snip]
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    Moderator Response: Inflammatory snipped.
  24. Tom @9, what proxy did the NOAA reconstructions use? Surely it's relevant that the Antarctic Peninsula was by and large grey, i.e. little or no data existed for the region at the time this reconstruction was done? So Lu's paper fills in a couple more blocks, but so far doesn't contradict any of the evidence that the MWP wasn't global. At least not that I can see.
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  25. caroza @24, unlike "is evidence of", "contradicts" is a very strong evidential relationship. So no, SFAIK, the ikaite evidence does not contradict the any of the evidence that the MWP was not global. That does not mean we should not adjust the probability we assign to the statement that "the MWP was global" in light of the ikaite evidence, and that evidence requires us to adjust that probability so that the statement is more probable than it was prior to our obtaining that evidence.

    Having said that, "the MWP was global" is a very vague phrase, that could be interpreted as meaning (a) "the MWP was associated with climate impacts of global extent" where the climate impacts could be anomalous cold as much as anomalous warmth outside of Europe. On that interpretation it almost certainly was global. Alternatively it could be interpreted as meaning (b) "the mean global temperature during some period in the MWP was greater than the 20th century mean (or the mean of the first decade of the 20th century)" with the first being probably true, although close to 50/50, while the later is possibly true but unlikely on available evidence. Or it could be interpreted as meaning, (c) "The regional temperature in all regions of the globe was greater than the 20th century mean during some of (or most of) the MWP", which is almost certainly false in the first case, and absurd on the available evidence in the second.

    It is probable that Lu et al meant something like (a) when they wrote that "...our ikaite record builds the case that the oscillations of the MWP and LIA are global in their extent...", although they could have meant something like (b). It is probable that Watts meant something like (b) or stronger. Never-the-less, without specific clarification we cannot just assume Lu et al meant (a) and that Watts meant (b) and that therefore Watts misinterpreted Lu et al.

    The ikaite evidence is evidence for all of (a), (b) and (c) and their variants, and does not contradict the contraries of any of (a), (b) and (c) or their variants which is why I have not clarified before.

    Finally, Mann et al 2009 use a largely overlapping proxy set to that used in Mann et al 2008, whose proxy records are kept by NOAA. Mann et al 2009's data is probably also kept by NOAA but I do not have the link to hand.
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  26. The regional variation in MCA remains an interesting question, but note that modelling runs in AR4 does predict MCA as a global event.
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  27. "Yes, I know, I covered it first"

    The WUWT article has been edited since first publication and doesn't have a time stamp. However, the first comment - by David A - is dated and timed at March 22, 2012 at 7:06 am.

    The story was covered by Kompas.com on the 22 March at 10:53 WIB. I stand ready to be corrected, but my understanding is that the Earth isn't flat, so for the same calendar day, 10:53 WIB is substantially earlier than 07:06 in the US.

    So: who covered it first? Or perhaps the better question would be: who covered the story accurately first?
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  28. Is a review of the paper coming soon?

    It may be interesting. But there is a annoying paywall that blocks any intersted readers that are not subscribed to Earth and Planetary Science Letters
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  29. From Peru - I'm not aware of any SkS author addressing this particular paper.
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  30. Watts: the authors at Syracuse themselves are under pressure because the alarmosphere has gone ballistic over the possibility that Mike Mann’s “there is no MWP much less global” gospel might be challenged

    Watts: What’s your point? That the author is now tap dancing? No doubt he was given a talking to.

    That's one way to avoid admitting error - imply the author's statements to correct obvious widespread mangling of his work are not sincere - that he is the one spinning his own work because of some shadowy pressure from somewhere. These claims alone are disgraceful.

    Can someone enlighten me as to what this "there is no MWP" gospel is that Watts speaks of? Published work (ex. Mann 2008, Mann 2009) appears to show otherwise. Does Dr. Mann not follow his own gospel?

    Tom Curtis: Had Watts himself supported the Mail Online's claims, he would have no refuge to hide in.

    Citing junk material without critique is simply irresponsible. While issuing an update on the same post 3 days later might seem redemptive, the vast majority of readers won't see it. That's part of their general communication strategy: shoot first ask questions later, and make sure those questions are answered quietly.
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  31. "Medieval" as an adjective applies only to European Middle Ages, which lasted roughly from the end of the Roman Empire (5th century AD) to the Renaissance (15th Century AD). The Discovery of America by Columbus in 1492 is generally considered the end of the Middle Ages, and the start of the Early Modern Period.

    But you will not hear any historians talk about "Medieval New Zealand", or "Medieval Brazil". So "The Medieval Warm Period was a Global Phenomenon" makes as much sense as saying "The 14th Century Black Death was a Global Phenomenon". Both statements have some meaning, but is very imprecise, and needs further explanation.

    There was always evidence for what I have seen called the "Little Climatic Optimum" in the North Atlantic from 950 to 1250AD. I think it was H.H.Lamb of CRU who first used the term Medieval Warm Period in print. Lamb meant Europe only, as he displayed a chart with temperature records from England.

    There should be some effort to stop using the term Medieval Warm Period. I think North Atlantic Climatic Optimum should be used for the 95-1250AD period with warm temperatures, to emphasise there there is no evidence that it extended worldwide.

    To confuse matters, deniers grab published temperatures from places like China at a time other than 950-1250AD, and annex them to the "Medieval Warm Period".

    The same consistency should apply to the Little Ice Age.

    However, I fear that the term Medieval Warm Period is too embedded in the consciousness to be changed.
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  32. shoyemore @31 makes an interesting point about nomenclature. Things are a little more confused than he suggests however. For a start, historians do refer to Medieval Japan (1185-1600), Early Medieval China (220-589 AD), and Medieval India (1206?-1596 AD). However, Shoyemore is correct that there is no medieval Brazil, or New Zealand. I believe that only societies developing a feudal organization with a late iron age physical culture can be said to be medieval. Clearly these various medieval periods overlap, but are not synchronous, so naming a purportedly global phenomenon after its near synchronous timing with the european high medieval period is, therefore, eurocentric at the least.

    However, renaming the MWP the Little Climactic Optimum or the North Atlantic Climactic Optimum is of dubious merit. One well established feature of the period 900-1500 AD is a series of very long, strong La Nina like conditions in the Eastern Tropical Pacific. It follows that, at a minimum the ETP was unusually cool over that period (and the WTP unusually warm). These are not North Atlantic conditions, and nor were the La Nina like conditions climactic optimums either in the ETP or in some effected areas. Similarly evidence exists of persistent cold conditions in Russia at this time. This mix of persistent warm and persistent cold conditions in various distinct parts of the globe indicate that the best name is a Climate Anomaly, and absent any convenient global name for the period, the Medieval Climate Anomaly will have to serve (Eurocentric though it is).

    Unfortunately, while more accurate, that choice of names will involve us in a fruitless rhetorical debate that the fake "skeptics" prefer so much to discussing science. Hence I'll stick with MWP for now.
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  33. NWJ @30, I agree that citing junk material without debunking it is unjustifiable. I just think it is a shame that was not the focus of the criticism of Watts. On that point he clearly has no leg to stand on, and cannot plead that he or the paper is being misinterpreted.
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  34. Like Tom Curtis, I think criticisms of Anthony Watts in this topic are unfounded, and I think it's incredible nobody has retracted any of them. However, I am dismayed by Curtis's decision to offer Mann 2009 as evidence to contradict a position. Mann 2009 is based on the same analysis as Mann 2008 was, and this means it suffers from the same problems. Specifically, it is entirely dependent upon tree ring data and uncalibratable data (which was used upside down).

    This point was even acknowledged by Gavin Schmidt:

    Note too that while the EIV no-dendro version does validate to 1000 AD, the no-dendro/no-Tilj only works going back to 1500 AD (Mann et al, 2009, SI).

    In fact, the Supplementary Information for Mann 2009 acknowledges its dependency on that data. Given this dependency directly contradicts Mann's 2008 paper, it seems peculiar to offer either paper as evidence of anything to do with the MWP.

    Incidentally, unlike BaerbelW's representation @18 and Dave123's representation @20, there are many people who believe a high MWP is important not because it disproves AGW, but rather, because it indicates natural variability may play a larger role than is commonly believed.
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  35. Brandon, interesting. However, I am puzzled by this:
    "Specifically, it is entirely dependent upon tree ring data and uncalibratable data (which was used upside down)."

    The list of proxies in the supplementary data includes many different types of proxies. Is it your contention that these other proxies (spelotherms, icecore, coral etc) are "uncalibratable"?
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  36. Also, I note support for Mann 2009, in Graham et al 2010 which makes interesting reading. Also, Brandon, by "natural variability" do you mean "unforced variability"? Modelling does not support this idea.
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  37. Here's my very first public prediction.

    Within a decade, today's hotly debated issues surounding the "Medieval Period" will be nothing more than a footnote in disussions of manmade climate change.
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  38. scaddenp, that's not my contention at all. What I and Gavin Schmidt are discussing is if you remove tree ring data and a few other series (known as the Tiljander series), Mann's conclusions are unfounded. While there are over a thousand proxies used in Mann's paper, it turns out almost all of them are irrelevant to the conclusions regarding the MWP. The only things which matter are the uncalibratable Tiljander series (which were used upside down) and tree ring data. The other series may be fine or not, but they aren't the source of the signal, so to speak.

    As for natural/unforced variability, I was referring to natural variability as I presume there would have been some sort of forcing involved. However, it would be understandable to think natural fluctuations play a larger role if we don't know of any forcing which could have caused the MWP.

    As for modeling, that's an important point. The argument would be if the MWP was warm (and not limited to a few regions), and we can't explain it, it should cause some doubt as to the explanations we have.
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  39. Brandon, what I am noting is that the idea that there are known forcings operating in Medieval Period is unfounded. Figure 6.13 in AR4, WG1 notes work on known forcings and also model responses to those forcings at least for the NH. This doesnt resolve questions about SH response nor explain the regional variations in response (though Graham et al would suggest that these are resolvable).

    The idea that there was some unknown forcing/variability at work at MWP which could also be responsible for modern warming is clutching at straws to my mind. We have perfectly good explanation with known physics and forcings for today's global warming.
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  40. scaddenp, if we accept that the idea you mention is "unfounded," and we accept a high MWP, there are only two possible conclusions. One, the current state of knowledge regarding forcings (which ones exist or the ones present in the MWP) is rather lacking. Two, natural fluctuations can be much larger than is currently believed. Whether or not it seems like "clutching at straws" to your mind, those are the only two sensible conclusions.

    Both cases would have a meaningful impact on our current state of knowledge, and thus it is worth knowing. It's even possible the final result would be climate's sensitivity to certain forcings is larger than expected, and thus global warming is a more serious problem than expected.

    As for having a "perfectly good explanation with known physics and forcings for today's global warming," that's mostly a non-sequitir. If estimates of climate sensitivity have a range of over two degrees, there is obviously plenty of room for impact.

    It's important to remember plenty of people don't think a warm MWP would mean AGW was untrue, but would still be important.
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  41. Whoops! That should read "..no known forcings operating.."
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  42. scaddenp, nobody is suggesting there were no (known) forcings operating during the MWP. Forcings exist at all times. The question is one of magnitude. Consider these two questions:

    If the MWP could be as warm as current times without anthropogenic influences, how can we explain it? If we don't have an explanation, how do we know the same cause isn't have an influence now?

    It's also worth pointing out if the MWP truly was warm, it calls into question the manner in which the "consensus" has formed. How could the hockey stick have gotten such prominence if it was wrong (especially if it was critically flawed)? How could so much effort have gone into defending the hockey stick if it is wrong?

    The point of the MWP isn't that it will overturn AGW. It's that it will provide valuable information.
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  43. Brandon Shollenberger @34 objects to using the use of Mann et al 2008 and 2009 because, according to him, the signal disappears if you exclude both all dendroclimactic (tree ring width and tree ring density) proxies and all Tiljander series. Mann et al 2008 used a total of 1,209 proxies, of which 4 where Tiljander series and 1,036 are dendroclimactic series. Removing both leaves just 169 or the original 1,209 proxies series. Brandon thinks it significant that having removed 86% of the data, the signal no longer remains intact. I think that tells us more about Brandon than it does about the reliability of Mann et al 2008 and 2009.

    However, it is possible to partially test Brandon's contention by consulting the supplementary information of Mann et al 2008, where we find the following chart:



    You will notice that the reconstruction using just 14% of available data (no dendro) is not significantly different from the full reconstruction, especially using the CPS method. You will also notice that even using the no dendro data set, peak MWP temperatures in the NH are still less then their peak in the 20th century.

    On the face of it, therefore, there is no merit in Brandon's claims. As he has provided no supporting evidence, his claims should be dismissed until he supports them with actual data, and actual sited quotes (if he wishes to claim somebodies authority for his position).
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  44. To me, Brandon's #42 is somewhat of a microcosm of the problems with a certain style of arguments on the topic.

    The first two paragraphs imply (the logical extension of them) that if we don't know with precision the forcings during every bout of climate change over the life of the planet, we can't have much confidence in our conclusions on the modern rapid warming, particularly if the value of globally-averaged temperature happened to be similar to recent times. This is like saying that if you buy a used automobile with an incomplete service history, you can't have any confidence in being able to diagnose problems. Certainly, it could be useful to have the complete record, with every dotted I and crossed T, but ability to make conclusions based on current and recent observations are hardly diminished, nor is the fact that current and past data (that is available) is entirely consistent with how we know a car engine operates.

    Sadly, the reliance on relatively simple but compelling non-sequiturs explains why so much effort went into attacking past reconstructions, something that continues today. That reminds me - I need to read Mann's recent book. Probably some better insight there on the matter.

    But of course, analogies aren't perfect. Neither are proxy reconstructions, or any measurements for that matter. This relates to Brandon's 3rd paragraph. First, as an important background, what does it mean for the MWP to be "warm"? Brandon does not define "truly was warm". Does this mean that there were many regions warmer than their average over the last 1000 years? Not in any real dispute. Does this mean that there were individual proxies or regions equal to or exceeding warmth in the recent period? Not in dispute either - it's even stated in Mann 2009. Does this mean that global mean temperature was warm relative to its average over the 1000 years? Again, not much dispute there that I've seen. Does it mean that global mean temperature was the same or warmer than the recent period? What is the range of the MWP? Some proxies show peak warmth at different times within that period, or sometimes after it. What is the "recent period"? 20th century average? Average of the last 3 decades? Average of the recent decade? Note also that many reconstructions just make conclusions for the northern hemisphere. The arguments put forth bring up a whole host of these questions, not completely covered here, and never sufficiently detailed by those who choose to "over-interpret" proxy data. CO2science.org comes to mind. "Mann tried to erase the MWP" or Watts' definition of Mann's gospel being "there is no MWP" are other phrases that seem to jump out. Erasing what exactly? Some sketchy Lamb proxy from Central England from the 1960's? We end up with a whole series of silly strawman arguments whenever some proxy is found to be, for deliberate carelessness effect, "truly warm".

    Next, all reconstructions are "wrong" in the sense that they aren't precise or perfect representations, so this isn't a useful term. Past reconstructions have error bars, and they tend to be larger going back further. The early MBH northern hemisphere reconstructions had fairly large error bars from the MWP. Even then, with the most "flat" early reconstructions, the best estimate showed a northern hemisphere temperature relatively higher than, say, 600 years later. The error bars allowed for significant variation. A significantly more pronounced MWP is consistent with these past reconstructions.

    There are plenty of questions about what exactly qualifies a reconstruction to be a "hockey stick", but that's another matter.

    Brandon's final paragraph is correct, but not very useful. Valuable in what way? To present a more precise picture of climate events? Or to fool elements of the public (with fallacious reasoning) into believing either global warming isn't a problem, or we just don't have any clue? For scientists, the former. For political hacks, the latter.
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  45. To add to the comments about the mediæval warm period, its relative effect, and its extent, it's worth considering the data from Kyoto Cherry Blossom Festival in Japan.

    The Japanese have kept scrupulous records, extending back for more than a thousand years, that document the commencement of cherry tree flowering. Cherry blossom burst is highly temperature dependent, and Aono et al have carefully collated and analysed the records. The nice thing about the cherry blossom data is that it is a dataset independent of tree rings, and easily understood by the lay person.

    I commented on the data just over 18 months ago. I'll leave the intersted reader to follow the link for the extended commentary, but the basics are that:

    1) cherry blossom data tracks the proxy amalgams of other research groups
    2) there is a strong hint that the "mediæval warm period" extended to Kyoto for at least some of the mediæval interval
    3) the "mediæval warm period" in Japan was not as warm as are temperatures there now: there is a very distinct "hockey stick"
    4) the region around Kyoto appears to be warming relatively more than the global average, as indicated by the comparison of proxies.
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  46. Tom Curtis, I wasn't aware I would need to provide links for major developments in a paper you promote. (-snip-). However, I'm always happy to provide sources, so here is a link to Gavin's remark.

    Now then, you claim "to partially test [my] contention" by looking at Mann 2008's SI despite the fact I specifically said the 2009 SI acknowledged my point. (-snip-).

    In any event, you can find the SI I referenced here. In it, you'll find Figure 8 which shows what I said. The only difference is it removes the four Tiljander series and three other series which aren't relevant to what we're discussing.

    Finally, you say you think the sensitivity test I mentioned says more about me than the reliability of the work in question, yet that sensitivity test is specifically brought up by Michael Mann. It's even in the abstract of his 2008 paper. The only thing I add to the test he proposes is the removal of uncalibratable (and upside down) data. (-snip-), there is no difference between what I discussed and what Mann himself discussed. It's a strange issue to criticize me over.

    Incidentally, I don't claim removing 86% of the data is necessary to remove the hockey stick. I only go with that test because Mann himself specifically claimed his reconstruction passed it. And Mann's own work has acknowledged that isn't true. As has Mann's major supporter and friend, Gavin Schmidt.

    The same thing happens when you remove a much smaller portion of the tree ring data, but I thought it would be best to stick with the points people like Mann and Schmidt acknowledge as true before discussing other issues.
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    Moderator Response: [DB] Please refrain from personal characterizations and stick to the discussion of the science. See the Comments Policy for further guidance. Inflammatory tone snipped.
  47. Brandon Shollenberger @46 thank you for the links. However, having been able to peruse their contents, it is quite plain why you did not provide them previously.

    Let's start with Figure S8:



    Your original claim was that Mann et al 2009 was "... entirely dependent upon tree ring data and uncalibratable data (which was used upside down)."

    By examining the graph above it can be seen the the essential features of the Global Mean Temperature Reconstruction without dendro series, the four Tiljander series, and three other series which may have suspect data. Specifically, that reconstruction shows a LIA colder than the 20th century average, and a MWP warmer than the 20th century average but colder than end 20th century temperatures. The only way in which the reconstruction could be considered "entirely dependent" on the tree ring and tiljander data (combined) is on the issue of statistical validation. But it is no surprise that as you reduce the number of proxies, the period over which the reconstruction passes statistical validation reduces.

    Indeed, the reason the reconstructions loose statistical skill with increased duration is that the number of proxies available for the full duration of the reconstruction falls. By excluding dendro plus seven other series, the number of available proxies in the period 1400-1499 after screening drops from 99 to 22. With dendro series still included that number rises to 68. So, it turns out that Brandon's case depends on arguing that the fact that 22 proxies is insufficient to reconstruct global temperatures is some how of great statistical significance.

    Of course, he has an authority on his side, Gavin Schmidt. Except it turns out that what Schmidt actually wrote was:

    "It's also worth spelling out some of McIntyre's thimble hiding here. First off, after a 7 years you'd think that he would be aware that the reconstructions are done in a step-wise fashion - i.e. you use as much information as is available as far back as you can. Back to 1500 you use everything that goes back that far, back to 1400 a little less etc. So a proper no-dendro/no-Tilj reconstruction will not just be made with what is available in 1000AD. Second, given all of the bluster about validation statistics, he never seems to compute any. Since the no-dendro CPS version only validates until 1500 AD (Mann et al (2008) ), it is hardly likely that the no-dendro/no-Tilj CPS version will validate any further back, so criticising how bad the 1000 AD network is using CPS is hardly germane. Note too that while the EIV no-dendro version does validate to 1000 AD, the no-dendro/no-Tilj only works going back to 1500 AD (Mann et al, 2009, SI). So again, McIntyre is setting up a strawman, not performing any 'due diligence' and simply making stuff up - all in order to demonstrate some statistical prestidigitation to the adoring commenters."



    So, instead of affirming that the lack of validation for the no dendro, no tiljander data set prior to 1500 is some show significant, he is excoriating McIntyre's "thimble hiding", thimble hiding of a very similar nature to that by Brandon.

    If Brandon was serious about his argument, he would perform a Monte Carlo test. He would eliminate 1,039 proxy series and determine the earliest date at which the resulting reconstruction achieves validation using the Mann et al 2008 method. He would then rinse an repeat, doing the same thing several thousand times to find a probability function for the duration of statistical skill for similar trimmings of the proxy set. If, having done that he finds that statistical skill is preserved well earlier than 1500 AD in >95% of cases of similarly extensive censoring of the data, then he has a case. Failing such a test, however, all he as is the trivial fact that significantly reducing available data significantly reduces statistical skill.

    [sarc] Who would have thought it? [/sarc]

    Finally, Brandon says:

    "Incidentally, I don't claim removing 86% of the data is necessary to remove the hockey stick. I only go with that test because Mann himself specifically claimed his reconstruction passed it. And Mann's own work has acknowledged that isn't true. As has Mann's major supporter and friend, Gavin Schmidt."


    This is a straightforward falsehood, or actually several of them.

    1) Neither Mann nor Schmidt claimed that reducing the data "remove[s] the hockey stick". That is explicitly a claim about the shape of the curve resulting from removing the data, and as can be seen above removing the data does not significantly change the shape of the curve. More importantly, Mann and Schmidt made claims about the effect of censoring data on statistical skill, not on the shape of the curve.

    2) In Mann et al, 2008, Mann made claims about statistical skill when removing all dendro series. He did not make any claims about statistical skill when removing all dendro series plus seven other series. Therefore the supplementary information to Mann et al 2009 does not show his claim in 2008 to have been wrong.

    3) As Mann et al 2009 does not show Mann et al 2008 to be wrong, Schmidt cannot have acknowledged the non-existent error by citing the non-existent acknowledgement of the error.

    Given that the quoted claims by Brandon are direct falsehoods, I would hope he has the integrity to acknowledge his error, and correct it. But I fear he will just provide one more example of the truism, being a denier means never having to say your wrong.
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  48. While on the topic of correcting errors, two days ago I posted this on WUWT:

    "Anthony, granted that the passage you quote is reasonable grounds for the claim that the study provides evidence that the MWP was global, so long as we interpret “provides evidence” in a strict but weak sense which does no over interpret the data. Specifically, it does not establish a prima facie case that the MWP was on average warmer than the first decade of the 21st century, or that all locations of the globe where warmer than the first decade of the 21st century (two possible interpretations of the claim that the MWP was global). It does contribute towards building such a prima facie case, but other evidence contributes to building the contrary case and only by consideration of the balance of all evidence can it be determined which theory is better supported.

    However, the Daily Mail article clearly misrepresented the contents of Lu et al, 2012. Nor did we need the corrections from Syracuse University and Dr Lu to know that. Specifically, the article claims that ikaite is “a rare mineral that records global temperatures”, which is blatantly false. It also claims that the study “Throws doubt on orthodoxies around ‘global warming’” which is also blatantly false (and tendentious). Given these clear misrepresentations by the article, why did you not provide a caveat with your link warning your readers of the misrepresentation by the Mail Online? This is of particular interest as, by your account, this post is for the benefit of people who have read the Mail Online article and were wondering why you had not posted on the topic. Surely for their benefit it was important to point out not only that you have covered it, but that the Mail Online article contained gross misrepresentations, and to correct those misrepresentations.

    I await your answer with interest."


    So far Watt's has not deigned to respond. Evidently acknowledging and correcting the errors he did make on this paper, ie, his failure to point out the gross misrepresentation by the Mail Online article to which he linked, is not on his agenda.
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  49. Tom Curtis #32

    Yeah, yeah, I would go with Medieval Climate Anomaly as a vernacular, but I think no journal editor should accept a sentence like "The Medieval Climate Anomaly was global", but prefer "The Medieval Climate Anomaly, observed in Europe as a warming between 950 and 1250AD, extended to other parts of the planet." Or not!

    You are correct of course that the word "Medieval" is extended to region outside Europe which had parallel feudal organisations at some point between the 5th century and the 15th century. All the more reason to try to remove the vagueness the term brings to the discussion, which detracts from the science.

    BTW, some great posts of yours above. Well done.
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  50. "If the MWP could be as warm as current times without anthropogenic influences, how can we explain it? If we don't have an explanation, how do we know the same cause isn't have an influence now?"

    Firstly, warming is not the same as current times. Even historical records have different regions warming at different times, unlike current setup. And only in a few places is warming comparable to present. Whether the MWP was a global phenomena is open question but proxy evidence to date does not yet support that nor does the weak sealevel signiture.

    Secondly, as I pointed out earlier,when the postulated forcings operating in MWP are put into models, then they show warming at least for NH. (For reference papers, see the AR4 figure). The mystery is in the regional pattern, not the absence of sufficient forcing.
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