I just noted over at CA that Michael Mann has linked to a photo of college students at Union College celebrating his Hockey Stick, even now, in a new 2013 exhibit on climate change.

This discussion is for any comments, reflections, and links on the current status of the Hockey Stick controversies. I think it would be useful for interested BH denizens to try to pull together what can or should be learned by now about the various Hockey Stick papers, is there any lasting value to Mann's work after all the corrections and controversies are reviewed, etc.

Mann loves his Hockey Stick

Michael Mann continues to celebrate and promote his Hockey Stick even now, in 2013:

What did Talleyrand reportedly say of the Ancien Regime (quotation may be apocryphal),

"Ils n'ont rien appris, ni rien oublié"

“they have learned nothing and forgotten nothing”

a few items I find helpful for context and background info:

Brandon Shollenberger's book review of Mann (2012) "The Hockey Stick and the Climate Wars"

Brandon Shollenberger's technical review of Mann's (2012) book

BH thread with links -- Brandon Shollenger's review of Mann (2012) "The Hockey Stick and the Climate Wars"

Hilary Ostrov, "Sunday shocker: Michael Mann misrepresents … again"

Thanks Chris M, I suspect you are right (I hope so) about where attention and energies should be focused as/if Mann is increasingly marginalized. However, for non-scientists like me who want to have some idea of "what it all means" after years of Hockey Stick controversy, I'd simply like to get a sense of what the take-aways should be.

I quite agree that anyone who can contribute to the scientific and public controversies on a national and international scale should now concentrate on issues other than Mann's work. I am not one of those people, but more of an interested spectator to it all. I don't want to distract anyone who has more important things to do in these areas -- I merely hope for some discussion by those who still like to assess Mann's impact now and over the past 14 years.

note: I am going to post some links and comments of others from through the years, various places, simply to try to get a collection of some salient points in the Hockey Stick Wars. I understand that a lot of people on various sides view these discussions as passe, BUT I think that so long as Mann & friends are jetting around the world pretending that almost none of the criticism and corrections matter, then there is still much that needs to be resolved. Both for "the record" and for the sake of integrity in science and public policy.

I found this comment at Pielke, Jr. (from Oct. 2009, in a discussion of "upside down" data from lake sediments) to be a very helpful take on how Mann & co. have managed to prolong these debates for years:

succinct summary of one Mannian method

50. Tom C said...

Roger -

To reduce this issue to the simplest form, Mann is (as always) fishing for a correlation. He throws in anything that has a large 20th century uptick whether the methodology was bad (BC pines) or the interpretation is wrong (varve thickness). He says "you can get a stick without trees" (look, nothing in my left hand) as he includes the varves; then he says "I can get a stick without Tiljander" (look, nothing in my right hand after the ball was transferred from the left hand) as he puts the BC pines back in.

When this game is challenged, his fallback is "teleconnection".

Trying to pin him and his assorted defenders down is, as Steve notes, an effort to follow the shell game.

Wed Oct 28, 08:16:00 AM MDT

For operations of "The Team" in protecting their precious stick, few stories can be as revealing as the sordid machinations behind

Caspar and the Jesus Paper

Thanks, Diogenes -- yes, I've been wondering when there might be indications that Bouldin's critique is getting proper attention. He indicates that he has quite a tale of frustration at trying to get some of his analysis published. I hope he will keep at it and find some serious interest. Quite 'interesting' to see one of the RealClimate team on such a path....

Thanks David Ross, I look forward to reading your article! fyi, those weren't my words about "I don't think he's worth bothering with" but I appreciate your attention to this discussion thread. Also, John Shade (and Shub) just provided most elegantly the kind of perspective I am groping toward myself, on the "Spot the Difference" thread about the Met Office. I am going to reproduce John Shade's long comment here because I think it helps to put this thread in the perspective I was looking for, in case anyone does wish to comment here:
=========================================================================

[John Shade, on the "Spot the Difference" thread, comparing uses of Hockey Stick to work of the Met Office]:

I think the irresponsibility of climate science workers is highlighted here by shub ( 1:18 AM ):

How is the near-term natural variability not relevant to global warming? Imagine you are in the year 1988. Hansen walks up to the US Senate and tells the world that it would warm. The next 10 years of warming are taken unequivocally to be due to anthropogenic CO2. These ten years could very well have been due to 'natural variability' but that explanation was never allowed, was it? And now it is?

It was irresponsible of Hansen to make such testimony and irresponsible of his backer Wirth to have opened so many windows the night before that the air conditioning could not cope during the hearing [http://www.pbs.org/wgbh/pages/frontline/hotpolitics/interviews/wirth.html].

It was irresponsible of the Met Office and others not to point out, loudly and clearly, that the subsequent warming decade was not necessarily due to the additional CO2. Lindzen, on the other hand, did show responsibility back then and since, and his sensible perspective is standing the test of time. For example, from his 1989 presentation at MIT:

"I argue that the greenhouse effect does not seem to be as significant as suggested." Professor Lindzen said. He spoke last week before an audience of 250 scientists at the Alexander von Humboldt Foundation Colloquium at Kresge Auditorium. "I personally feel that the likelihood over the next century of greenhouse warming reaching magnitudes comparable to natural variability seems small," he said. "And I certainly feel that there is time and need for research before making major policy decisions."

[http://www.fortfreedom.org/s46.htm]

It was irresponsible of John Houghton to make so much of the MBH Hockey-stick plot within the IPCC, and irresponsible of the Met Office and others not to have thoroughly audited such a study purporting to erase the MWP before giving it such credence. Thank goodness there were responsible adults in the form of McIntyre and McKitrick to do that job later. Thank goodness also that we have an outstanding piece of writing on this part of the history of science. It is called ‘The Hockey Stick Illusion’ [http://www.amazon.co.uk/Illusion-Climategate-Corruption-Science-Independent/dp/1906768358]

It has been irresponsible for the Met Office to act as if computer models are capable of being run to give climate forecasts fit for practical guidance. Buried within even the IPCC documents are statements that they are not fit for prediction.

In sum, a strategy must recognise what is possible. In climate research and modelling, we should recognise that we are dealing with a coupled non-linear chaotic system, and therefore that the long-term prediction of future climate states is not possible.”

The pantomime-like record of Met Office attempts at seasonal forecasts would be laughable were it not for the harm they must have caused. It is generally better, after all, to have no forecast than to have a wrong forecast that discourages preparations against a wider range of plausible conditions. Stocking less road grit, and less de-icer at airports, are but two examples of responses to a forecast of a milder winter to come.

The biggest fail of all has of course been associated with the [flatlining] of nominal global mean temperatures for the past 16 years or so - a spectacle that might well be puzzling the concerned citizen who has been soaked in exponentially rising temperature projections, and convinced that CO2 is the culprit. Mind you, I am not aware of the mass media going big on this flatlining, so perhaps my imagined citizen is not yet puzzled. But one day, that puzzlement will arrive and ought to be followed by considerable anger. But will a raging citizenry be any match for the unbounded sophistry of computer climate modelers?"Our computer models can do flatlining - we've always known that. You can expect that from time to time. So we're not wrong. We can't be wrong. The science is settled. One day the warmth will come. Just you wait and see."

And, of course, one day it will get warmer year after year as measured by global means. Cue a renewed crescendo of alarm about over-heating. Then it will get cooler again, year after year. Cue a new offensive spun around climate disruption making things colder. And, from time to time, those mean temperatures will not do much, year after year. Cue the hunt for and press releases about extreme weather events. Or maybe not. Maybe one day, we’ll just see that stuff on sandwich boards on the High Street alerting us to the end of the world.

Jan 11, 2013 at 10:35 AM | John Shade

As noted on Unthreaded..... some say all hockey stick issues are passe, but there is plenty of legal and policy fire still burning:

Mann's lawyers present Wahl and Amman (2007) as gospel

Subsequently, every peer-reviewed study that has examined McIntyre and McKitrick’s claims has found them to be inaccurate. (note 26)

26
See, e.g., E.R. Wahl and C.M. Amman, “Robustness of the Mann, Bradley, Hughes Reconstruction of Surface Temperatures: Examinations of Criticisms Based on the Nature and Processing of Proxy Climate Evidence,” Climactic Change, 85 (2007); 33-69, available at: http://www.cgd.ucar.edu/ccr/ammann/millennium/refs/Wahl_ClimChange2007.pdf; E.R. Wahl and C.M. Amman,“The Importance of the Geophysical Context in Statistical Evaluations of Climate Reconstruction Procedure,” Climactic Change, 85 (2007); 71-88, available at: http://www.cgd.ucar.edu/ccr/ammann/millennium/refs/Ammann_ClimChange2007.pdf

Physicist Robert G. Brown of Duke U. (rgbatduke) posted a lengthy comment in the Bob Carter thread at WUWT which provides valuable context of the kind I have wanted to summarize here, about how the Hockey Stick has functioned since its introduction in 1998/99. I don't have a WordPress account so I can't link to the specific comment (so far as I know), but here is a substantial excerpt with a link to the main thread itself. The Carter post and much of the thread is valuable for a review of where some of the climate debates stand:

rgbatduke comment at WUWT

rgbatduke says:
January 30, 2013 at 9:02 am

TheBigYinJames says:
January 30, 2013 at 12:59 am
Good article, one small beef though: Although it pains me to say it, the lack of warming in the last 16 years does not automatically void the assumption of a link between CO2 and warming, because there could be hysteresis, time delays in the system.

I don’t personally believe this to be the case, but since it’s a possibility, it would be foolish to ignore it in these sorts of discussions until we have passed a period where it can’t possibly be a fluctuation (they keep expanding the definition of this time period, but I would say 20 years would pretty much cover it)

[rgbatduke]:

You are quite correct, but you failed to note his discussion about the null hypothesis. The entire point of the hockey stick graph from the beginning is that without some supposedly credible curve that “erased” the MWP and LIA and replaced them with a flatline up to an industrial era hockey stick increase, nobody would ever have drunk the IPCC kool-ade in the first place!

That is, if it was really just as warm (within noise) in the MWP or the RWP as it is today (as apparently it was) without CO_2, it is very difficult to argue that it is only as warm as it is today because of CO_2. If the LIA was really the coldest single century in eleven thousand years (as apparently it was) than it is hardly surprising that the Earth might spend several centuries warming back up from it, a process that occurred independent of CO_2 levels and that continues similarly independent today.

That’s the point of the “natural variability”. Michael Mann became famous strictly because he managed to cook up a graph that utterly eliminated it on a millennial time scale, erasing the evidence of natural variability altogether so the current variation could be blamed on CO_2 and human influences. Humans really aren’t that dumb — sheer common sense would have prevented most people from buying the CAGW or DAGW (is this a renamed, kinder gentler version of CAGW, one where warming is merely “dangerous” and no longer “catastrophic”?) hypothesis when there was nothing extraordinary about the present compared to the past. It still would, but at this point the big lies have already been told, and a thousand small lies support them. There is a large social-inertia mass to be moved and only the weight of truth to move it. Historically that weight is up to the task, but it often takes decades to centuries to work.

So you are dead right. The C/DAGW hypothesis has not been disproven. Nor has the hypothesis that the next glaciation is going to start in 2014, with the coming solar minimum ushering in a century or more of unrelenting cooling in the teeth of increased CO_2, as occurred before during the Ordovician-Silurian transition — an ice age where the minimum CO_2 concentration in the atmosphere was roughly 10x that of the present, and where the ice age began with CO_2 concentration 17 times higher than it is today. Nor is the hypothesis disproven that the climate will be dead on stable within 0.2C for the next century. Nor is the hypothesis disproven that magnetic monopoles exist and are the correct explanation for the quantization of charge.

This is why the null hypothesis is so important, especially in arenas where we have little real understanding and our theories at best weakly explain only certain aspects of the data in a non-unique way. In the next decade, it might warm, cool, or remain the same. Do we really know enough to predict which one?

Probably not.

If you’d gotten all of the members of the IPCC together in 1998 and forced them to bet on whether the 33 year anomaly at the end of 2012 would be a whopping 0.2C, with no statistically discernible warming since 1998, you could have gotten any odds you like from them on a bet of no. They would have said no, no, no, absolutely impossible, I’ll bet you ten dollars to a dime that it cannot happen.

But it did, and continues to happen. The only significant cliimate event of the last 33 years appears to be the 1997-1998 super El Nino. Nothing else mattered. Not CO_2, not volcanoes, not aerosols, not black soot. And what caused that ENSO event? Surely not CO_2 — it was an accidental confluence of several chaotically oscillating events and (very probably) a pair of back-to-back strong solar maxima. CO_2 may have contributed — one expects CO_2 alone to contribute roughly 0.1 C/decade of warming along its current path of increase — but there is no plausible explanation for ENSO events being caused by CO_2 levels, or even a theory for how they might affect them. There is no quantitatively predictive theory for ENSO events at all....

ah, I just realized that it is easy to get the exact link to a specific comment at WUWT:

rgbatduke comment on WUWT's Bob Carter thread

One need simply click on the date/time below the username of the comment. The font is small and I had not recognized that the date/time stamps are clickable!

Steve McIntyre re-posted (last year) the following, which is a statement he posted in 2005 discussing how the hockey stick "matters" even though it's such flawed science. Still relevant today because the iconic imagery is widely perceived as relevant even if informed observers know better.

Does the Hockey Stick Matter?

Posted Mar 16, 2012 at 11:30 AM

For those interested in whether the hockey stick “matters”, here is an editorial on the matter that I submitted to Roger Pielke’s blog in November 2005, nearly 7 years ago. I don’t think that anything has changed much, other than the “community” itself being tarnished by their mismanagement of the issue.

Stefan Rahmsdorf and others (including Roger Pielke, the proprietor of this site) have taken the position that the Hockey Stick is irrelevant to the great issue of the impact of 2xCO2 on global climate. Even the originator of the Hockey Stick, Michael Mann, who received many awards and honors for its construction, ironically has taken the position that it doesn’t “matter”. (I do not believe that he has not returned any of the honors.) I’m inclined to agree that, for the most part, the Hockey Stick does not matter to the great issue of the impact of 2xCO2. However, I believe that it matters (or should matter) to IPCC, to governments that relied on IPCC and to climate scientists who contributed to and supported IPCC and to people who may wish to rely on IPCC in the future.

The Hockey Stick was not, as sometimes portrayed, an incidental graphic, buried in IPCC TAR. Nor was it an icon resurrected by sceptics purely to torment poor Michael Mann. It could almost characterized as the logo for IPCC TAR. Figure 1 below shows Sir John Houghton, at the press conference releasing IPCC TAR, standing in front of the Hockey Stick. The graphic was used repeatedly in IPCC TAR and was one of the most prominent graphics in the Summary for Policymakers. Some governments (and, the Canadian government in particular) relied upon it in their promotion of Kyoto policy even more than IPCC. In the lead-up to adopting Kyoto policy, Canadians were told by their Minister of the Environment that “1998 was the warmest year of the millennium and 1990s the warmest decade”. So even if the Hockey Stick did not “matter” to the scientific case, it mattered to the promotion of the scientific case. Scientists may want to “move on”, but institutions cannot, if they want to maintain any credibility. If the Hockey Stick was wrong, it would be as embarrassing as the failure to find WMD in Iraq. In both cases, the policy might well be justified on alternative grounds, but the existence of the alternative grounds does not mean that responsible agencies should not try to isolate the causes of intelligence failure and try to avoid similar failures in the future.

The issues surrounding the MBH Hockey Stick are complicated by IPCC TAR statements and decisions, which, in retrospect, seem misguided, although there is little to suggest that IPCC AR4 is taking to steps to avoid similar potential problems. The most questionable IPCC statement about the Hockey Stick is that the MBH98 reconstruction had “significant skill in independent cross-validation tests”. I added bold to highlight the plural—a second level to the misrepresentation contained in this claim. The statement appears to have been written by Michael Mann about his own work. It is now known that the MBH98 reconstruction in the controversial 15th century portion failed the majority of cross-validation tests, including the standard R2 test [McIntyre and McKitrick, 2005a]; the source code provided to the Barton Committee shows that the adverse cross-validation R2 statistics were calculated, but not reported. It is also now known that the MBH98 reconstruction does not live up to its warranty that it is robust to the presence/absence of all dendroclimatic indicators, as the reconstruction depends on the inclusion of bristlecones, a series known to be potentially contaminated as a temperature proxy. Again, this adverse information was known to the authors and not reported.

If I were in Houghton’s shoes, I would be mad as a boil about all this. Since Houghton has a sincere belief that the impact of 2xCO2 is the great issue of our times, then, if I were Houghton, I would be particularly angry at being placed in a position where I used this logo and wasn’t fully informed about adverse information pertaining to it. I also wouldn’t be leaving it up to some probably adversarial committee like the Barton Committee to sort this out. I’d be all over the problem so that my community, the community of climate scientists, was not further embarrassed and so that government institutions would be able to rely confidently on the opinions of IPCC.

If I were Houghton, one line of argument that I would not accept is that the other “independent” studies all say similar things. It was the Mann study that I stood in front of. If there are serious problems in it, which were known ahead of time and I didn’t know about them, I would carve everyone involved a new you-know-what. Now for public purposes, I’d feel a lot happier if I could at least retreat to the safe haven of other studies that showed something at least similar to the Mann study. But I’d be pretty worried about them on a couple of counts and I’d want them torn through from top to bottom. The first thing that would worry me is that the studies were not really “independent”. The coauthors all seem to swap places: you see Mann, Jones, Briffa, Bradley, Cook, Schweingruber – all well-known scientists, but all having coauthored together. I’d be worried about a monoculture and want a fresh set of eyes. The second thing that would worry me is that the same proxies are used over and over – the bristlecones, the Polar Urals etc. I’d be worried about systemic problems. I’d be worried that no one seemed to have gone through these other studies like M&M had gone through the MBH studies. Maybe there are more time-bombs. I wouldn’t just passively wait for them to go off.

If I were Houghton, I would be enraged at the public refusal by IPCC authors to show their data and methods. When I read in the Wall Street Journal that Mann had said that he would not be “intimidated” into showing his algorithm, I’d have taken immediate action; I’d have told Mann to stop acting like a prima donna, to archive every line of code and data used in MBH98 and stop fighting a pointless battle that simply embarrassed IPCC and the entire field of climate science. I’d have done more than that. I’d have notified everyone contributing to IPCC that we did not expect the same kind of nonsense any more, that anyone contributing to IPCC would have to ensure that their archives of data and methodology were complete or else we couldn’t use their articles. I’d have done so before I heard from some redneck Republicans.

I would also review how we were checking studies in IPCC AR4. If our very logo for IPCC TAR blew up on us, then something was wrong with our procedures for review. I wouldn’t go around patting ourselves on the back and telling everyone that this was the most “rigorous” review procedure in the history of science, since we’d goofed on such a prominent issue. I’d want to know why we goofed and how to avoid it in the future, or at least, how to minimize the chances of a recurrence. So when some redneck tried to use the Hockey Stick fiasco against IPCC, I’d at least have an answer.

A final thing that I’d ask myself: if this damn chart is “irrelevant” to the great issue of 2xCO2, why did we use it at all? And why did we rely on it so much in our sales presentations? Why didn’t we just talk about the issues that were important and stay away from little irrelevant stuff? Maybe I’d find out, when I investigated, that someone had decided that this was merely for sales promotion – the climate equivalent of a sexy girl sitting on a car. If that were the case, I wouldn’t necessarily be happy about it, but at least I’d understand it. Then I’d want to make sure that we were also selling steak as well as sizzle. I’d sure want to make sure that we’d really done a good job on the issue which Ramsdorff and others now say was the “real” issue: climate sensitivity to 2xCO2.

Here I’d be bothered by how little guidance we actually gave to policymakers interested in an intermediate-complexity analysis of whether 2xC02 will lead to a temperature increase of 0.6 deg C or 2.6 deg C or 5.6 deg C. When I re-examined the TAR, I’d notice that we’d virtually skipped over these matters. I’d think: it’s not enough just to list all the results of different models; let’s try to figure out why one model differs from another, what are the circumstances under which a model gives a low sensitivity and what are the circumstances that a model has high sensitivity – if that’s the “real issue”. When I saw that we’d barely touched this sort of analysis in IPCC TAR, I’d be pretty embarrassed. I would certainly vow that in AR4, we would not repeat the mistake of ignoring the “real issues” in favor of hood ornaments.

The other thing that I wouldn’t do is simply ignore the problem and hope that it goes away of its own accord. I wouldn’t rely on the assurances of Mann and similar protagonists that the various alleged defects do not “matter”. No corporation would do so in similar circumstances and IPCC shouldn’t either. I would long ago have got some independent statistician to see if there really was a problem that I should be worried about. I wouldn’t have stood still for this water torture. I’d tell Mann to co-operate with the investigator and request McIntyre to cooperate. I’d try to get the parties to sign off on an exact statement of points and issues that everyone agreed on and ones that were in dispute. Once I saw what was in dispute, I’d ask for what would be involved to determine once and for all who was right on specific issues. I would long ago have gotten tired of barrages from both sides, where I couldn’t be sure that they were not at cross-purposes.

So does the Hockey Stick matter? Yes, if you’re a climate scientist that believes that the IPCC is an important institution whose opinions should be valued. Mann now thinks that the Hockey Stick does not matter. As so often, life is full of ironies.