Hit somebody! (The hockey song)

0901hockeythumb.png Expect a renewed interest in the shape of hockey sticks, as a new paper in the Proceedings of National Academy Of Sciences (PNAS) by Michael Mann (et al) finds that the last decade was the warmest for at least 1,300 years. The BBC headlines the story “Climate “hockey stick” is revived”, which rather stretches the facts about the controversy (nicely covered in the piece). More coverage at Mongabay, which notes:

The results confirm that temperatures today in the Northern Hemisphere are higher than those of the Medieval warm period, a time when the Vikings colonized Greenland are are believed to have become the first Europeans to visit North America.

Sounds like a red rag to sceptic bulls to me. Expect much nit-picking and fulmination. The rest of us will get on with trying to sort out the problem.

Mann et al. (2008). Proxy-based reconstructions of hemispheric and global surface temperature variations over the past two millennia. PNAS September 9, 2008 vol. 105 no. 36 (PDF available here)

80 thoughts on “Hit somebody! (The hockey song)”

  1. Yes – sorry – I’ve been trying to find a solution to that edit problem. It’s a server issue. The last one left, I hope, after the move.

    The different colours in the spaghetti graph are the different studies using different proxies/mixes of proxies.

  2. Anyhoo… The infamous hockey stick! That would be an actual record (disputed, unscientific, and poorly collected) nailed onto the back of proxy measurements then. Ah, new science! We might as well consult crystals and hang a piece of hemp over a map to find future warming.

  3. Gareth – what do you think about this?

    Caspar and the Jesus paper
    Monday, August 11, 2008 at 08:42PM
    There has been the most extraordinary series of postings at Climate Audit over the last week. As is usual at CA, there is a heavy mathematics burden for the casual reader, which, with a bit of research I think I can now just about follow. The story is a remarkable indictment of the corruption and cyncism that is rife among climate scientists, and I’m going to try to tell it in layman’s language so that the average blog reader can understand it. As far as I know it’s the first time the whole story has been set out in a single posting. It’s a long tale – and the longest posting I think I’ve ever written and piecing it together from the individual CA postings has been a long, hard but fascinating struggle. You may want to get a long drink before starting, and those who suffer from heart disorders may wish to take their beta blockers first. [snipped]

  4. bi – – IJI. Another inspiring post I see from you – with a brilliant riposte. Two bits of advice. When you feel the tip of the cotton bud come up against something, pull it back out of your ear. Also, when you pick mushrooms in the woods, don’t eat them! That’s where you’re going wrong, my friend!

  5. Bomber. Good piece. There will be lots about this in the coming months, especially with regard to the MWP. Has Climate Audit got its teeth into yet? Roger Pielke has.

  6. Wouldn’t say I don’t like him, just never see a constructive post based on the issues. Exhibit A: The above. And have you read his blog? Great, if you’re an insomniac.

  7. Dear Gareth

    The paper is publically accessible via the PNAS front page and going to the early edition.

    It looks to be a good piece of work. Clearly written.


  8. OK guys, Bomber’s legit.

    That piece is a very one-sided view of what Macintyre’s been up to at Climate Audit. It’s nit-picking about the statistics used in a ten year old paper that’s been supported by all the work done since. “Bishop Hill” is a regular commenter at CA, and his world view seems to be determined by that tight little sceptic clique.

    PS: I’ve edited your comment to link to Hill’s blog, rather than clutter up the comments here….

  9. bomber:
    the Bishop Hill piece is full of insinuation, i.e. certain damning conclusions are encouraged without any good reasons to reach them being spelled out–such and such was “quietly” accomplished, this and that “duplicitous” arrangement was made. It looks like any other conspiracy theory to me. Extraordinary claims, such as professional misconduct, require extraordinary evidence, which does not appear to be offered in that piece. I think it fairly portrays what a lot of McIntyre’s crowd *thinks* happened, but that does not demonstrate that it is what *did* happen. I am in no position to offer proof in either direction, so that’s just my two cents about what can be gleaned from the way the piece is written. In any case, McIntyre is about to have a whole new round of fun looking at the new paper; we’ll see what comes of it.

    Whatever happens, it is the mark of a certain type of delusion when someone thinks that if they can cast doubt on one piece of the evidence about anthropogenic warming, that will somehow call the whole large-scale picture into question. It seems that some people don’t understand what “multiple independent lines of evidence” means.

  10. Bishop Hill’s piece makes a lot of noise about how the IPCC desperately needed the Wahl and Ammann paper in Climate Change for the AR4… but I just scanned the Paleoclimate chapter and it’s only cited once (Ch6, p466), and only in connection to the first McIntyre-McKitrick paper’s failure to replicate MBH98. Of the criticisms about verification steps that Bishop Hill brings up, the IPCC actually says:

    McIntyre and McKitrick (2005a,b) raised
    further concerns about the details of the Mann et al. (1998)
    method, principally relating to the independent verification
    of the reconstruction against 19th-century instrumental
    temperature data and to the extraction of the dominant modes
    of variability present in a network of western North American
    tree ring chronologies, using Principal Components Analysis.
    The latter may have some theoretical foundation, but Wahl and
    Amman (2006) also show that the impact on the amplitude
    of the final reconstruction is very small (~0.05°C; for further
    discussion of these issues see also Huybers, 2005; McIntyre
    and McKitrick, 2005c,d; von Storch and Zorita, 2005).

    Whatever your opinion on the statistical arguments, the insinuations of malfeasance and conspiracy on the part of the IPCC just look like bullshit.

  11. Tortoise – I think you nailed it. The Caspar and the Jesus paper looks like ‘State of Fear’ has slipped the bonds of fiction and leaped into fallacy disguised as fact. It’s the methodology and rhetoric rather than the plot and that I find most interesting (my occupational hazard, I’m afraid).

  12. Fragment and others

    Thanks for your interest in the Caspar piece. In answer to Fragment’s points, the Wahl and Amman paper found that you could retain the hockey stick shape under a proper centred PCA calculation if (and only if) you retained the fourth principal component of the North American Tree Ring network. In the original hockey stick paper, it was claimed that it was only necessary to take the first PC. Using decentred PCs makes a huge difference therefore (and this is what Wegman testified to Congress). The fourth PC accounts for only 8% (IIRC) of the variance in the network, so it’s pretty hard to claim that it’s a significant pattern in the data. To put it another way, Mann’s original argument was that tree rings from a couple of species of trees in a couple of mountain ranges in a corner of Colorado were the most important pattern (PC1) in tree rings in the USA and that they could therefore be used to form the basis of a recreation of temperatures across the northern hemisphere. Now the argument is that the tree rings from these obscure trees are indeed very obscure (PC4), but they can still be used to recreate northern hemisphere temperatures. It’s simply not credible.

    On the subject of verification statistics, the paragraph you quote from the IPCC does a rather cute sidestep doesn’t it? – they move swiftly on to principal components while leaving one with the impression that the criticisms of verification stats has no foundation at all. But this is all out in the open now. W&A have admitted that their reconstruction has R^2 of zero. A statistically insignificant reconstruction cannot prove that another statistically insignificant reconstruction is correct.

  13. Thanks for showing up Bishop. I feel like leaping into Monty Python mode and shouting “It’s da bishop”, but that would be childish. (I’d forgotten how funny that sketch is…).

    So let’s cut to the chase. Do you really think that the contested statistical minutiae to which you refer somehow mean that the world is not currently warmer that at any time in the last 1,300 years?

  14. Bishop, thanks for dropping by. Please note that my comment above was in response to your inferences that the IPCC was up to something dodgy based on the idea that Wahl & Ammann (2007) was highly important to them. Whatever the merits of the PC1/PC4 centred/decentred arguments (and I don’t agree with you), that was not an argument you raised in the piece linked by bomber.

    The argument you did make was that the IPCC depended on the Wahl & Ammann (2007) paper’s verification statistics. Fact is I just demonstrated they aren’t mentioned in the WG1 report, and the whole topic of MBH98 & MBH99 is brief. As such, statements like “the IPCC needed to have the Wahl and Amman papers in the report” are completely unfounded, on the evidence you’ve given. You wouldn’t accept shoddy reasoning like you’ve presented from, say, Al Gore, and I’m not going to accept it from you.

    And the fact is that it undermines your credibility. When you’re wrong about easily fact-checked material like that, I’m not really inclined to go through and see if the claims you make about the actual statistics bear up under scrutiny. If you want to convince someone like me of something about the quality of the science, stick with the science please, and stay out of the realms of dodgy inferences about motivations.

  15. In view of Gareth’s words, ‘The rest of us will get on with trying to sort out the problem.’, I thought it worth mentioning that the Royal Society has just released a dedicated theme issue of Philosophical Transactions of the Royal Society:
    ‘Today, the individually neutral words ‘global’ and ‘warming’ combine to provide an epithet whose consequences, already causing misery and premature death for millions, hold the prospect of unquantifiable change and potential disaster on a global scale for the decades to come. While the link between rising global temperatures and increasing atmospheric concentrations of CO2 has been known for more than a century, there is increasingly the sense that governments are failing to come to grips with the urgency of setting in place measures that will assuredly lead to our planet reaching a safe equilibrium.’

    The twelve papers are a collection of possible geo-engineering solutions to deal with what the editors further describe as an ‘inadequate response by politicians’.

    I say fascinating, but it’s more a gut-clenching kind of fascination, particularly the paper on ocean fertisilization (I have not yet read them all). The RS has published this theme issue in order to generate serious discussion. What’s alarming is that, well, the RS are not known for being alarmists.
    Access to the journal is via the usual databases or directly: http://journals.royalsociety.org/content/102021/?Content+Status=Accepted&sort=p_OnlineDate&sortorder=desc&v=expanded&Proposed+Issue+Title=Theme+Issue+‘Geoscale+engineering+to+avert+dangerous+climate+change’+compiled+by+Brian+Launder+and+J.+Michael+T.+Thompson

  16. 1) This newest result looks like another few bricks+mortar in “The great Wall of Science” I described in part 1 of this long post at Deltoid. It extends the Wall, and firms up the earlier work.

    2) When one has a bunch of long-ago reconstructions, with error bars, and they mostly overlap, even if they don’t agree exactly, a rational person says:

    – We don’t know the exact answer.
    – But we don’t need to, it’s most likely in the middle somewhere.

    – Put another way, if X says something is 10 +/- 2, and Y says it’s 10.5, +/- 2, they mostly agree, not disagree.

    3) Iff people consider England as an area that displayed a clear MWP+LIA temperature pattern to be representative of areas like that … there’s a delicious, quite-well-documented 2000-year temperature history that supports it’s warmer now in England than it was any other time in the new Mann reconstruction.

    Anybody know what that is? (Hint: it’s buried somewhere in that Deltoid post.)

    4) Not that it really matters, except to general scientific understanding…
    What matters is the current temperatures, current Ocean Heat Content, and the expected trajectory of planetary energy imbalance.

    The average temperature in 1000AD makes *zero* difference to what’s coming, although bounding it better will help people make better predictions.

  17. Gareth

    The answer is that we have no idea if the twentieth century warming is unprecedented or not. The idea that you can resurrect past temperatures from tree rings is a bit mad IMHO because of all the confounding factors (rainfall, relationships with other organisms, genetic changes and so on). There is a great deal of evidence for a Medieval warm period from non-tree ring sources, although I wouldn’t suggest for a moment that these demonstrate conclusively that medieval temperatures were higher than today.

  18. Fragment

    We know that the IPCC broke its own rules by accepting W&A’s paper for the 4AR when it hadn’t been accepted for publication. You could argue that this was “just one of those things”, but I don’t think it’s terribly unreasonable of me to think that there might have been a reason for this. None of my other arguements depend whether the paper was accepted legitimately or not, so it’s a moot point anyway. To say it undermines my credibility is entirely fallacious.

    Regarding the PC arguments, I didn’t cover these in the original posting, you are right. The article has been widely discussed as a summary of the hockey stick affair, but this is a misconception. It was only telling the story of Wahl and Amman’s papers, so the PC issue was left out. You say you disagree with me. Would you care to elaborate on that a bit? Wegman says it’s wrong. Gerry North (who headed the NAS panel) says he agrees with Wegman. What do you know that these guys don’t?

    I didn’t say that the IPCC needed to have W&A’s verification statistics as such. I said that they needed to have W&A because this was the paper that was alleged to refute McIntyre & McKitrick. With this alleged refutation in place, they could continue to use the hockey stick to promote the idea that modern warming is unprecedented. The bit about verification statistics demonstrates that W&A’s papers didn’t refute M&M at all – in fact they showed the same thing, namely that the hockey stick had no statistical skill.

  19. We know that the IPCC broke its own rules by accepting W&A [Wahl and Ammann]’s paper for the 4AR when it hadn’t been accepted for publication. […]

    […] I said that they needed to have W&A because this was the paper that was alleged to refute McIntyre & McKitrick.

    M&M’s paper was published in Energy and Environment, which isn’t even a credible journal. The IPCC didn’t even have to include M&M’s work in the first place. They did not have to find a paper to refute M&M, but they did — as a goodwill gesture.

    So, Hill, is it suddenly OK to bend the rules, as long as doing so supports your inactivist position?

    — bi, International Journal of Inactivism

  20. I don’t think it is meaningful to try to make precise temperature comparisons across hundreds or thousands of years. But I would happily say this is probably one of the warmest periods in the last few thousand years, and could be the warmest.

    But I am intrigued by the “hockey stick” graph you post. I have always disliked this particular graph because, even if the data is accurate, the data presentation seems misleading to me. The later data-sets, showing the strong upward swing, are not smoothed nearly as much as the older datasets. The raw data shows fluctuations that encompass huge swings in temperature, but these are smoothed out in the graph, except for the few recent data-sets. Yet it is these few recent data-sets that provide the dominant visual effect. So the dominant visual effect, of a sharp upward spike at the end, seems to me to be an illusion created varying the smoothing between the temperature series.

    Although there are clearly differences, the smoothing methodology is not clear; but I expect the older data-sets are smoothed by adjacent periods, whereas the Had and Cru data sets look as if they are smoothed by prior periods with the addition of a trend line. I bet you dollars to donuts that if the exact same methodologies applied to the last 20 years of the Had and Cru datasets were applied to each 20 years of the other data records, we would see many many similar peaks in temperature.

  21. Bishop:

    we have no idea if the twentieth century warming is unprecedented or not

    Oh really? It doesn’t just depend on tree rings, you know. There’s a mass of evidence from all sorts of proxies, as well as the physical response of the climate system (see Arctic melt). And that’s really my frustration with the whole “hockey stick” business – that somehow playing around with statistics and “auditing” other people’s work is supposed to be a counterbalance to what John Mashey memorably described as the “great wall of science” (it’s worth following his link, it’s more relevant to what’s really going on than the tale you tell).

    Meanwhile, the rest of the world will get on with trying to do something to alleviate the problem. But thanks for showing up.

  22. Bi
    Where a paper was published is not relevant to whether it is correct or not. To argue otherwise is a fallacy. The chief criticisms of the hockey stick (the use of decentred principal components and failure of the verification R^2) were in Geophysical Research Letters rather than E&E anyway.

    I don’t understand the rest of your comment.

  23. Gareth

    As I remember it, the IPCC 4AR is pretty much all about multiproxy reconstructions. I can’t recall anything from the last 2000 years section that doesn’t include tree rings. I may be wrong though.

    What non-tree ring reconstructions do you have in mind? I can think of Loehle’s (which Bi wouldn’t like it because it was in E&E :-)) but that was too late for IPCC anyway. And it showed an elevated MWP. Everything else is contaminated by tree rings and, more particularly, bristlecones and a few rather dubious other series like Gaspe and Tornetrask.

  24. Bishop Hill:

    Where a paper was published is not relevant to whether it is correct or not. To argue otherwise is a fallacy.

    Yeah, indeed, and of course it’ll be absolutely acceptable for them to cite a paper from my International Journal of Inactivism. After all it calls itself a journal, and some of the articles have been peer-reviewed (well, reviewed by peers)!

    Or not?

    The chief criticisms of the hockey stick […] were in Geophysical Research Letters

    …happen to be not the ones that the IPCC were dealing with. The above-quoted paragraph from 4AR talks about

    independent verification of the reconstruction against 19th-century instrumental temperature data

    which is simply not discussed in M&M’s GRL paper. The idea that the IPCC needed W&A to rebut M&M — specifically M&M (GRL) — is fiction.

    — bi, International Journal of Inactivism

  25. Bi

    You seek to denigrate M&M by saying they published in an obscure journal. I pointed out that this is fallacious and that the chief criticisms of the hockey stick were published in GRL, a major journal, (and by the way, the journal that had originally published MBH99.

    You then refer to a part of Fragment’s IPCC quote about independent verification. You left out the second part of the quote which is about principal components. This was in the GRL paper, so to this extent at least, your attempt to defend the hockey stick on grounds of “the refutation was published in an obscure journal” is not only fallacious but wrong. The incorrect PC calculation, which has been peer reviewed in a major journal and confirmed as a valid criticism by two major independent scientific panels, means that the hockey stick is wrong. End of.

    Now, as to the independent verification of the HS by other researchers, M&M05 (E&E) criticised the allegedly independent verifications of the HS on the grounds that the researchers were not independent of Mann, Bradley & Hughes, and also that they used many of the same proxies too – and that the proxies that were driving the results was, in pretty much every case, down to bristlecones and foxtails (which were widely agreed – including by some of the hockey team – to be experiencing a non-climatic growth spurt in the 20th C) or to a small number of other proxies with alarming adjustments, and/or secret data (Tornetrask, Gaspe, Lonnie Thompson’s ice cores). This claim was examined by Wegman, confirmed as correct, and indeed extended.

  26. Bishop Hill:

    You left out the second part of the quote which is about principal components.

    M&M (GRL) does not dispute the PCA calculation either; it disputes the preprocessing of the data prior to the PCA:

    prior to their principal components (PCs) analysis on tree ring networks, they carried out an unusual data transformation which strongly affects the resulting PCs.

    In other words, the so-called “main points” which the IPCC actually had to address were all in M&M (E&E). Take out the E&E tabloid article, and there’s simply nothing that the IPCC was obliged to rebut.

    — bi, International Journal of Inactivism

  27. Bishop:

    As I remember it, the IPCC 4AR is pretty much all about multiproxy reconstructions.

    Not the one I read. It seems to cover the multiple lines of evidence quite well.

  28. Bi

    I don’t think we’re going to get anywhere by debating the semantics of whether standardisation of the proxies is a pre-processing step or a part of the calculation itself. You can’t do PC analysis without having standardised the series you are attempting to analyse. If you get the standardisation wrong, then what comes out of the calculation isn’t a PC. Whichever way you look at it, MBH got it wrong and M&M said so in GRL.

  29. Bishop, I’m talking about the response of the climate system to forcing by GHGs, not the narrow question of multi-proxy reconstruction. There’s plenty of evidence that tells us the current situation is well out of what might be described as “the ordinary”.

  30. Two more set of bricks in the wall:
    1) I recommend Ruddiman, 2007
    , see especially section 10, where he further develops the plague/reforestration hypothesis to help epxlain teh CO2 jiggles of the post-Roman period and the LIA.

    2) But the other one, and there is a slight relevance to New Zealand, due to the relatively recent fondness for grapes, is the one I alluded to earlier:

    [SEL2004] Richard C Selley, The Winelands of Britain: Past, Present & Prospective, 2004 (F). Geologist/oenophile traces historical growth and shrinkage of UK wineries over two millennia. Current wineries are North of Medieval Warm Period and heading North quickly. Slightly out of date, a few vineyards are already in Leeds, Selley’s projection for 2050. Visit the Loch Ness winery around 2100AD. See map of Britain’s winers over last 2000 years.

    Selley has done extensive studies of the geology and archaelogy of British wineries, as summarized by the ebb and flow of them in the map.

    If the MWP/LIA happened in UK, then I observe that the Northern limit of winieries is already well above the MWP limit… Grapes are enough of a high-value crop that people do plant them where they can. Maybe someone in NZ can point to the historical spread of viticulture there

  31. John Mashey. I live in England. During the Roman occupation 2,000 years ago they grew vineyards as far north as Northumberland (look it up on the map – you’ll be shocked). As far as I’m aware, we’re nowhere near that today. Must have been the fault of all those Roman Chariot 4x4s!

  32. Harry the Hat:

    0) The MWP was (roughly) 1 millenium ago.
    The Roman period was (roughly) 2 millenia ago.

    The latest Mann, et al paper talks about reconstructions to 1300 years ago (~700AD), and maybe, with tree-rings/caveats to 1700 years ago (~300AD), so there’s not a lot of overlap with Romans in England (~ending 450AD?). I didn’t once mention Roman period, nor did Mann’s paper, because, as far as I know, we don’t yet have anywhere near the proxy evidence people would want to make strong statements.

    BUT, since you raised the interesting issue of Roman times…

    1) I don’t live in England, but my wife is from Yorkshire, I’ve been to England maybe 30 times, so I know where Northumberland is.

    2) I conjecture you got the “Roman vineyards in Northumberland” from one of the usual unreliable blogs, and stated it as an authoritave fact without checking, but if you have an actual reference to serious research, with a specific location, please post it, as people would be delighted to see it. Otherwise, it might be nice to just say “I saw it on a blog, or wherever”.

    3) Of course, some of us do check things out, not just by reading , but by asking those far more expert than ourselves.

    A courteous email request often elicits a quick answer, so here, I asked Richard Selley what he thought, and he kindly replied within a few minutes.

    By happy chance, the newest edition of his book came out, and he has included more material on Roman period:

    a) He “does not know of any Roman vineyards as far nNorth as Northumberland. North Thoresby in Lincolnshire is the most northern to the best of his knowledge.”

    North Thoresby is about 25 miles South of Leeds (where vineyards exist), but nearer the coast, about 60m lower, and should be roughly 1-2C warmer than Leeds, in 2080, according to Selley’s latest map. North Thoresby would be in the pink (Merlot) area near the coast, whereas Leeds would be in the yellow (Chardonnay) area in the middle, as should Northumberland be, by then (top right corner). SO, Northumberland will get its chance.

    b) Now, that does *not* guarantee there were no Roman vineyards in Northumberland, it just means that a serious expert who has studied this for many years doesn’t think so.

    It also shows that people are already growing grapes a bit North, and in a cooler area than the most Northern Roman vineyard he knows. Of course, economics and technology might be different, and temperature isn’t everything, Hence I do not label this as overpowering proof of anything, but I certainly give Selley’s views weight.

    c) It does say: there isn’t a lot of evidence, but the vineyard evidence that does exist says:

    – England is already warmer than MWP
    – And maybe a little warmer than (later) Roman times.

    If anyone would actually like to understand the dynamics of all this, again, I recommend Ruddiman’s book:

    If our interglacial were like most past ones, without human civilization, and with the usual jiggles:

    – Roman times should have been cooler than they were [less CO2/CH4]
    – Medieval should have been cooler yet
    – And right now, it would be very cold, although nowhere near a return to the depths of an ice age (that would naturally be tens of thousands of years away, or now, possibly not to be seen again by humans).

    Most likely human agriculture and forest-cutting managed to cancel out the normal cooling, which was good, as it stabilized temperatures (and sea levels) in a very narrow zone … which are about to depart. Leaving too far in either direction will be very expensive, but it’s easy enough to stop the return to ice age, if anyone ever needs to. Unfortunately, the other direction is harder…

  33. John,

    Many thanks for that reply! You really should get yourself a repository for your longer – and most useful – comments.

    As it happens, I’m reading Plows*, Plagues and Petroleum at the moment, and finding his arguments compelling. The development of Ruddiman’s hypothesis and its progress is a far better example of how science really works than any of the bleatings of the sceptics.

    * – though I’d rather it was ploughs, obviously. 😉

  34. Bishop:

    No, you’re wrong. The only evidence for whether the current situation is out of the ordinary is paleoclimate.

    And there’s a lot more to paleoclimate than tree rings.

    So, do you accept the IPCC’s broad conclusion that warming is unequivocal, and action to restrict greenhouse gas emissions necessary, or does your “climate audit” bring the whole of Mashey’s “great wall” tumbling down?

  35. Bishop Hill:

    I don’t think we’re going to get anywhere by debating the semantics of whether standardisation of the proxies is a pre-processing step or a part of the calculation itself.

    So you’re now saying your assertion that ‘the IPCC needed W&A to refute M&M’ rests on a particular semantic interpretation of the above-quoted IPCC’s paragraph? That’s a rather thin strand to hang a whole edifice of conspiratorial motives upon, isn’t it?

    Besides, the IPCC specifically said that one of the concerns was about

    the extraction of the dominant modes of variability […] using Principal Components Analysis.

    rather than some vague concept of “calculation”. The IPCC’s concern was with the PCA itself, while M&M (GRL) was talking about preprocessing before PCA.

    So what the IPCC was really addressing was M&M (E&E), which they could rightfully ignore (but didn’t).

    — bi, International Journal of Inactivism

  36. John Mashey. I saw you post all this on realclimate! I didn’t say that you mentioned the Roman period. I mentioned it, just to prove a point that Britain was hotter 2,000 years ago than now. Ask your wife how we get our street names here – you’ll be enlightened. Britain is an old country. It’s town names, street names and even people’s surnames come from its past. As vineyards leave little archeological trace, they are hard to track down. However, there has been very much said about what the Romans did here, as you can imagine. So, no I didn’t get it from a blog – it’s just ‘known’. To go back to names. There are “Vine Streets” all over the UK etc. – even one in South Shields, Tyne & Wear, and one in Cumbria. Our ‘Central England Temperature’ tells us all that we’re 1 degree C warmer than we used to be. I have tried to find out (in vain) just how well that takes account of the urban island heat effect which, in a rather small and crowded country, is significant. But when you talk to older people here they poo-poo the idea of Britain warming, saying that it’s no warmer now than when they were kids. Alas, all we have is the CET. Cheers!

  37. Bishop Hill:

    I’ve been quite specific about what I’m talking about — I referred specifically to the IPCC’s above quote on the use of “Principal Components Analysis”, and to your baseless claim that the IPCC needed W&A to rebut M&M (GRL).

    You on the other hand have repeatedly been using vague terms like “calculation”, “argument”, and “the science”.

    It’s clear here who’s trying to conflate and confuse.

    The IPCC’s concern was with the PCA itself, while M&M (GRL) was talking about preprocessing before PCA.

    See what I mean?

    Oh yes, I know what you mean. You’re saying that The Argument™ based on The Calculation™ from The Science™ proves that Al Gore is fat. Or more specifically, it proves The Claim™, and now I forgot what The Claim™ was, because you keep using such vague terms. I mean, Terms™.

    Oh, and Al Gore is fat.

    — bi, International Journal of Inactivism

  38. Gareth

    Yes, I understand that there is more to paleoclimate than tree rings. We agree there. I’ve asked you to point me to a paleoclimate reconstruction that excludes tree rings, because the only one I know of that does this is Loehle (E&E, 2007) which puts the modern warming slightly below the MWP, IIRC. This being the case then we should not be panicking.

    I think that the conclusion that the world got warmer in the last few decades of the 20th century is reasonable. I think there are still some in interesting questions over the reliability of the various instrumental records but the various measures of temperature are consistent in trend I think, if not in absolute value. I think we have a reasonable feel for the way the temperature went after 1970. The more interesting quesiton is whether the current warming is unprecedented – warming happens all the time. I don’t think we know, as I said before.

    The question of whether to restrict greenhouse emissions is one where you don’t want to take the word of climatologists or any other part of John Mashey’s wall of science, because it’s a question of economics, not of science (unless you want to count economics as a science – and given most greenhousers enthusiasm for dishing E&E because it’s a social science journal, I don’t think you do :-)).

    I think action to reduce greenhouse emissions will kill a lot of people, mainly poor ones.

  39. Bi

    Can I just get one thing straight before I respond to your last point. Are you saying that Mann got the science wrong, but that you’re objecting to my suggesting that the IPCC needed the hockey stick? Or do you think that Mann actually got it right and that Wegman and North were mistaken? I mean, arguing with my saying the IPCC needed it is a pretty trivial objection in a debate about whether the hockey stick is bunkum or not.

    You seem to be trying to argue, quite seriously, that the main objection to the hockey stick was something to do with the principal components calculation (but not the standardisation of the data that went into it) and that this was in the E&E article. Well, I’ve referred to both papers, and the objection is the same in both of them – the data was transformed by subtracting the 1902-1980 mean rather than the full series mean, as is required by correct PCA, and this error gave undue weight to hockey-stick shaped series. So whichever way you look at it, the IPCC needed to address an argument which was in GRL. (I don’t know why we’re debating this anyway. You do insist on pursuing what I’ve already pointed out is a logical fallacy. And yes, even your humble journal of inactivity is capable of publishing something that is true and correct. It doesn’t matter where it is published, or who published it, or what their opinion is on Barack Obama. It only matters if it’s correct or not).

  40. but that you’re objecting to my suggesting that the IPCC needed the hockey stick?

    So Hill, are you backpedalling from your earlier claim that ‘the IPCC needed W&A to rebut M&M (GRL)’ to the weaker claim that ‘the IPCC needed the hockey stick’, so that you can later frontpedal to the stronger claim again?

    It doesn’t matter where it is published, or who published it, or what their opinion is on Barack Obama. It only matters if it’s correct or not

    Of course it does. You don’t like W&A because — by your own account — it wasn’t published in GRL. You went so far to say that

    the IPCC broke its own rules by accepting W&A’s paper for the 4AR when it hadn’t been accepted for publication.

    Or are you saying that the venue of publication doesn’t matter except when it does?

    — bi, International Journal of Inactivism

  41. You don’t like W&A because — by your own account — it wasn’t published in GRL.

    Huh? Where did I say this? This is simply not true. The quote you give immediately after this accusation has the meaning “it had not been accepted for publication” not “it had not been accepted for publication in GRL”.

    There are two separate issues here. Firstly the issue of whether the criticisms of the PCA in MBH98 and 99 were correct or not (you have avoided telling me whether or not you agree with Wegman and North that Mann got his statistics wrong). It is irrelevant where such criticisms were published, and I have been consistent on this question.

    The second question is whether the IPCC needed W&A to rebut McIntyre. I have shown in evidence the fact that they broke their rules to allow the W&A paper into the IPCC process. Whether W&A was published or not (or where) at the time of the closing date for submissions is irrelevant to the question of whether the statistics was right, but speaks directly to the question of whether the IPCC broke its own rules.

  42. Bishop:

    Citing Loehle? If you think that paper’s OK, then everything produced by Mann, Amman, Jones and the rest ought to be – by your standards – completely above reproach.

    Whether we need to restrict carbon emissions is not an economic matter. The fact of warming and its likely impacts are matters for real science. The economics comes in working out the response – not the need for action in the first place. And as most mainstream economists seem lost in a cornucopian world where growth can continue unconstrained by reality, you are right – I don’t have a lot of time for their advice.

  43. Gareth

    Loehle is the only tree-ring free reconstruction I know of. Can we agree that there aren’t any others? – you seem to be unable to name any either. So, there’s more to paleoclimate than tree rings. We agree. I think we also agree that the only alternative on the table is Loehle. I’ve read Loehle, and the corrigendum to it and it seems fair enough, but until I’ve studied the critiques, I don’t intend to draw any firm conclusions about it, so let’s accept for the moment your position that it’s not a good paper.

    Where does that leave us? The tree ring reconstructions are rubbish and you tell me that the only non-tree ring study is rubbish too. This would appear to confirm my position that we just don’t know if the current warming is unprecedented.

    I disagree with your position that whether action is required or not is a matter for the physical sciences. If the cost of, say, reducing carbon use is more than the cost of doing nothing other than adapting, then we shouldn’t do it. I think your position on economics makes you an “economics sceptic” (or perhaps an “economics denier”) 😉

  44. Folks, I now have this Bishop Hill chap posting on my site telling me that he isn’t getting his arse kicked here. I’ve watched the amazing discussions bounced around on this post and I am grateful that there is enough scientific mental grunt to mount these types of scientific debates on a NZ blog, and while I am no way an expert in this realm, I am a very keen observer of the debate and what I have noticed from this thread is that Hills original claims that I posted here where he attempts to smear Mann in some grand conspiracy, when really put to scrutiny, boils down to a very weak position of … Where does that leave us? The tree ring reconstructions are rubbish and you tell me that the only non-tree ring study is rubbish too. This would appear to confirm my position that we just don’t know if the current warming is unprecedented. … which when you compare to the original conspiracy posting is almost light years away in every sense.

  45. Bishop:

    I do not agree that tree ring reconstructions are rubbish, or that Mann got his “statistics wrong”. I certainly wouldn’t throw out a whole area of knowledge because of some imperfections – I would do what has been done, look at the criticisms, take them into account, and move on. The sad thing is that Macintyre and his followers don’t seem to be able to do that. In the wider context, paleoclimate studies are interesting and useful, but they are not the only game in town. They don’t determine the size or extent of the problem we face – they’re not so pivotal that “demolishing” the field will somehow remove the problem.

    And here’s a little theoretical dilemma for your team. Let’s imagine that the Medieval Warm Period was global, and as warm or warmer than today, which seems to be the goal of many of the anti-hockey stick team. If that were the case, they say, then there’s nothing unusual about today and we can stop worrying about CO2. Unfortunately for this argument, you can’t wish away the impact of CO2 – it’s basic radiation physics, well understood for a long time. So if the MWP was as warm as now despite lower CO2 levels in the atmosphere, then the climate system’s sensitivity to external forcing must be much higher than we think. If that’s the case, we’re really screwed!

    The key point with economics in the context of action on climate is that you cannot use economics to determine the size of the risk we face. Once we know what the risk is, we can turn to economics. It cannot help to decide whether or not we need to act, only provide some inkling of the “best” way to treat the problem. I’m happy to be an economics sceptic: I’m in good company (behind a paywall, sadly, but the intro will give you a flavour of where I’m coming from).

  46. Bomber,

    This really isn’t a scientific argument. No-one has started debating the finer points of principal component analysis or tree ring proxies (dry stuff at the best of times). What Bishop’s “Caspar” paper shows is how politicised the whole issue is in the minds of some people. There has been a huge effort, orchestrated by lobbyists and politicians in the US, to “discredit” the hockey stick. In scientific terms, they’ve failed, but in PR terms, and in the right wing blogosphere, they’ve succeeded in sowing confusion. So you get lots of opinionated commenters who think they “know the truth”, but who are really just regurgitating a line concocted in the think tanks of the neocon right in America.

    You might be interested in my attempt to demolish a couple of those over at Frogblog here.

    As for Bishop popping up around the place: some people do that. I must admit I do usually check out the “incoming links” on my blog’s admin page, but I usually resist commenting…

  47. Gareth, you’ve covered a lot of ground there!

    From the top the:

    Tree ring reconstructions are rubbish. I would suggest, by way of evidence, the fact that Mann’s verification R^2 for the AD1400 step was ~zero, indicating no statistical skill whatsoever. I would also suggest the divergence problem as another problem that hasn’t been surmounted. I’ve already mentioned the host of other factors (climatic and non-climatic) that can’t be controlled for. You only have to look at Mann’s laterst paper to see the huge divergence in recent years between the proxies and the instrumental records.

    On Mann’s statistics, you need to explain where Wegman and North are wrong. Just asserting that you don’t agree that he got the statistics wrong doesn’t form the basis of an argument.

    If tree ring studies can’t faithfully recreate past climate (verification R^2~0) then there is no point in making policy decisions based on them. As you’ve observed, there are other approaches and the paleoclimatologists should move on to these.

    I agree with you on the radiative physics – more CO2 will, other things being equal, lead to heating. How much heating is another question altogether though. As Mr McIntyre is fond of asking: “How do we get from a doubling of CO2 to 2.5C warming? Where is the explanation?”

    The point about climate sensitivity is an interesting one, because the current estimate is, I think, meant to explain the current warming. So if it’s wrong, then the models are all wrong, and another major plank of AGW theory is kicked away. On the other hand, we know that the CO2 levels have been much higher in geological history and the world survived OK, suggesting that a lower climate sensitivity to CO2 is in order. I guess what I’m trying to say is that you’re presenting me with a false dilemma. It isn’t “higher sensitivity” or “cooler MWP”. It could be something else entirely.

    You are right about economics not being able to decide the size of the risk we face. That is certainly one for the physical scientists. They can say “We face a 75% risk of 2C/century, a 25% risk of 3C/century and a 5% risk of 4C. Some other scientists can quantify what this means in terms of sea level rise, crop yields and so on. They can present alternative technological solutions. But then the economists have to decide which is the lowest cost solution, which may include “do nothing except adapt”. Do you agree that there are some theoretical circumstances in which adaptation is an option? Say if reducing CO2 were to kill half the people on the planet, while the cost of adaptation was £2.25 and a hangover on Monday morning? In these admittedly daft circumstances, nobody would choose CO2 reduction over adaptation.

    I don’t even think the idea of the solution being an economic question is even particularly controversial. The existence of the Stern report kind of proves the point.

    Your link to the NS piece is interesting – it could almost be from the introduction to an article about Austrian economics, which is something for which I have a lot of time. The only thing I ever got out of blogging was a review copy of Eamonn Butler’s “Best Book on the Market”. On page 6 he says: “Markets are human. They’re never perfect. If you own an economics textbook, you should rip out the section on ‘perfect competition'”.

  48. Bishop:

    No point trying to argue with you about tree rings and statistics. You have your view, I have mine. The most important difference is that you invest the issue with importance, whereas I regard it as a politically motivated sideshow.

    On climate sensitivity, you seem to think that if the models are wrong, then “another plank” is kicked away. Well, here’s news: the models are wrong, but they’re useful. They’re wrong, because they don’t get the Arctic right, and the changes there will cause rapid climate change (dig back here for more info), but they’re useful because they give us information about the way that the atmosphere and climate system work. They’re the best tools we have to examine the type of problem we face, and we need to invest a great deal of time and effort to make them better.

    I’m afraid you can’t wiggle out of the MWP/sensitivity issue by claiming a false dichotomy. For the MWP to be as warm as or warmer than today and truly global then the climate response to greenhouse gas forcing has to be higher than 3C. Even if climate sensitivity were at the low end of the scale, the sums wouldn’t work. However, as a metric climate sensitivity is not terribly useful, because it can tell us nothing about how the climate system will react in the future, particularly as carbon cycle feedbacks kick in.

    Macintyre’s question is irrelevant, and the fact that he doesn’t know (or doesn’t want to acknowledge) the answer says a great deal about his attitude to the subject.

    Developing an adequate picture of the risks we face is not a trivial problem. One big issue is that we are not in a position where we can turn the clock back on climate change. We are committed to a great deal of further change (the loss of the Arctic sea ice in summer, for instance) in the next few decades, and there is no physically plausible mechanism that will put that ice back on timescales of relevance to our civilisation. Adaptation is therefore essential and unavoidable. Many of the impacts of climate change are of this nature. The loss of an ecosystem service (clean water, for example) in a region, is not something easily compensated for by growth or future wealth. Intelligent planning for the future therefore has to include developing resilience to the impacts of climate change, and reductions in GHG emissions in order to prevent the longer term damages.

    If we had taken note of the first IPCC report and the big emitting countries had started on a low carbon development path back in the 1990s, we might have been able to put ourselves in a position where only modest adaptation was required. It is my view that we are now long past that point, and urgent action is necessary.

  49. Bishop Hill:

    I’ve been inviting everyone to dispute Wegman and North’s findings on PCA

    No, you’ve been making a big fuss over whether and where W&A’s paper was published. Why else did you refer to “the Jesus paper” in the title of your long rant? Why did you devote so much verbiage to the whereabouts of W&A paper, instead of its content?


    I am a very keen observer of the debate and what I have noticed from this thread is that Hills original claims that I posted here where he attempts to smear Mann in some grand conspiracy, when really put to scrutiny, boils down to a very weak position of … Where does that leave us? The tree ring reconstructions are rubbish and you tell me that the only non-tree ring study is rubbish too.

    Yes and no. As you’ve seen, the conspiracy theory is bull. At the same time, Loehle’s temperature reconstruction is not the only non-tree-ring-based reconstruction; indeed reconstructions excluding tree-ring proxies are part of what the latest Mann et al. paper discuss.

    — bi, International Journal of Inactivism

  50. Bi

    I meant on this thread, not in my original posting. I’ve asked both you and Gareth what it is you think is wrong with the conclusions of Wegman and North re Mannian decentred PCA.

    It’s good to have someone finally point us at an actual non-tree-ring-based reconstruction! Obviously, this is hot off the presses and I’ve not read Mann’s latest offering yet, although obviously the good people at Climate Audit are having a lot of fun with it. From what I’ve heard about it, the headline reconstruction is multiproxy though – I assume this means that he has tested for robustness to removal of dendro proxies (like he says he did for the hockey stick) rather than actually considering only non-dendro proxies. I’m not arguing that this is an incorrect approach – if there is valid information in tree rings, then there’s no point in not using it. The question is whether they are valid proxies or not.

    I think the animated GIFs at Climate Audit are fascinating. How does he process manage to process a load of data, very few of which have a hockey stick shape, in such a way as to make them the main pattern in global temperatures? If the proxies are valid you would expect to see upward rising twentieth century records in most of them. If the hockey stick is correct then you would expect to see another uptick in the medieval period in most of them. But the majority show no trend at all.

    This is one of the beauties of paleoclimatology. The data sets are sufficiently small that a layman can get a feel for what is actually happening in the data just by looking at them. The fact that a few hockey stick shaped proxies are being extracted from the data and hyped, if you like, as the most significant pattern is what sets the alarm bells ringing.

    So, I guess it remains to be seen whether Mann 2008 stands up to scrutiny. Are there any others non-dendro reconstructions you are aware of?

  51. Gareth

    Remember though that motivation is irrelevant to whether something is true or not. Even Karl Rove tells the truth sometimes!

    On the models, I agree that they are wrong but useful. I don’t actually know that much about the state of the models, but I always thought that “the way the atmosphere works” was an input to the models, not an output. If the paleoclimate reconstructions are wrong, and the models are wrong, what is the case for AGW?

    You are being terribly unfair to McIntyre. He has said he is looking for an explanation of how we get from a doubling of CO2 to 2.5C temperature rise. A proper explanation of the derivation of this figure doesn’t seem to exist. I’m sure you will agree that it should do though, given its prominence in the AGW case. I think people have a right to know the steps that are gone though to get from A to B, with the uncertainties at each step laid out.

  52. Non-treering based reconstructions (from IPCC AR4, Chapter 6):
    Oerlemans, J., 2005: Extracting a climate signal from 169 glacier records.
    Science, 308(5722), 675–677.
    Pollack, H.N., and S.P. Huang, 2000: Climate reconstruction from
    subsurface temperatures. Annu. Rev. Earth Planet. Sci., 28, 339–365.
    Pollack, H.N., and J.E. Smerdon, 2004: Borehole climate reconstructions:
    Spatial structure and hemispheric averages. J. Geophys. Res., 109(D11),
    D11106, doi:10.1029/2003JD004163.
    Pollack, H.N., S. Huang, and J.E. Smerdon, 2006: Five centuries of climate
    change in Australia: The view from underground. J. Quat. Sci, 21(7),

  53. BIshop:

    Models take the physics of the atmosphere (the same code that weather forecasters use) and marry that to the various forcings and feedbacks – ice/snow, albedo and ocean. When they’re run, how close they are to the observed patterns in the atmosphere is a measure of their “goodness”. They’re amazing achievements, but they’re not perfect – and nobody claims they are. The structures we see in the atmosphere are emergent properties of the models, not things programmed in.

    You seem fixated on finding something that will make the AGW case fail. Given that we understand radiative physics, and know where the excess gases have come from is quite sufficient to make a case for reducing GHG emissions. You (and SM) are being incredibly disingenuous about wanting “a proper explanation” of how you get from CO2 forcing to 3 (or 2.5C) sensitivity. I could recommend some good textbooks – in fact I have a link to Spencer Weart’s excellent Discovery of Global Warming in my sidebar, but I expect you want to find the “jesus paper” that lays it all out for you. Your loss.

  54. Gareth

    How is asking for an explanation of part of the case for AGW, which is being used to drive major policy decisions, “being fixated on something that will make the AGW case fail”? You seem to be implying that we should all sit back and take someone else’s word for it. Asking to have the case laid out in detail is not unreasonable. If it’s a good case it will stand up to scrutiny or anything that can be thrown at it.

    I don’t think a popular exposition from Spencer Weart is quite what is required. Something more like an engineering report, detailing the maths, the assumptions, the uncertainties and so on is what is needed. And besides, Spencer Weart’s piece barely mentions the issue, let alone providing a detailed explanation of how it is arrived at.

  55. Bishop:

    No, I’m not suggesting we should just take someone else’s word, but there comes a point when someone with an open mind looks at the evidence – all of it, from both sides, and decides who is more likely to be right. When you view the case for AGW in that light, there is only one winner, and it isn’t the sceptics.

    For the other stuff, why not try a climate textbook? Ray Pierrehumbert’s unfinished text is meaty and comprehensive, but demands pretty good maths/physics. If you prefer looking at code, there are plenty of publicly available climate models you could dissect. You should perhaps also remember that atmospheric physicists are not engineers…

  56. Bishop Hill:

    Obviously, this is hot off the presses and I’ve not read Mann’s latest offering yet, although obviously the good people at Climate Audit are having a lot of fun with it. From what I’ve heard about it, the headline reconstruction is multiproxy though – I assume this means that he has tested for robustness to removal of dendro proxies (like he says he did for the hockey stick) rather than actually considering only non-dendro proxies.

    Um, how about reading the paper first, especially since it’s only a link away? Then again, if you prefer to always wait for McIntyre to tell you what to think, then go ahead and do that.

    By the way, the paper does present separate climate reconstructions with and without tree-ring proxies (see Fig. 2).

    — bi, International Journal of Inactivism

  57. I’m please to report that my copy of Selly’s “The Winelands of Britain, Second Edition (2008) has arrived. It has substantial additions with regard to temperatures, and of course, it has a lot more current wineries listed.
    He lists 3 in Yorkshire, and 1 in Lancashire, i.e., North of the original 2050 estimate. there are now about 5X more wineries than at the height of medieval times, and maybe 10X more than during Roman times. I second Selley’s cautions on over-interpreting this data, but it’s clear that vineyards are heading North… and I still don’t place much credence in what “everybody knows” or that Vine Streets required vineyards to be named such 🙂

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