The hockey stick controversy is what drew me to climate science and here I am, several years later, still watching the skeptic blogs debate it and trying to break it as if it is a proxy for the whole issue of global warming.
This recent paper by McShane and Wyner is a case in point. In the greater scheme of things to do with global warming, the MBH98/99 papers and the graphic derived from it known as the hockey stick graph is relatively unimportant. It has attained a somewhat iconic status solely because of the controversy surrounding it and how skeptics have used and abused it to cast doubt on the reality of global warming. What we end up is round after round of face offs over the stick.
One wanders over to the skeptic blogs and finds that the hockey stick is still alive and well some 12 years later: a spectre haunting their dreams, with Michael Mann as the focus of their hatred — their whipping boy. There were two other authors of that paper, but I never — never — hear anyone speak ill of Bradley or Hughes. Mann is the Man, the focal point of the skeptic/denier/contrarian’s hatred, loathing and fear.
Seriously, the vitriol directed towards Mann and the Hockey Team, the hockey stick graphic and climate science over at the thread on WUWT is awe-inspiring and somewhat concerning. I read over at WUWT and see commentary that makes me question the mental health of some of the posters there. Why so angry? Why so worked up over a 12-year old graphic that has been replicated and then superceded by other graphs? I can only explain it by pointing out that the internet has become a place where crackpots of all genres can come together and obsess and rail about their own brand of nuttery.
It’s their thing. They hold up M&M like some David against Goliath, but in reality, it’s truly the other way around, but that’s for another post.
As I was reading McS&W2010, I was struck by the very political tone of the opening section. This didn’t seem quite appropriate for a scientific/technical/statistics paper. Frankly, it read more like the opening to a magazine or news article and undermines the credibility of the authors. Perhaps they are unaware of the effect of their choices on the reader, but I suspect not. Instead, the authors seem to be deliberately situating their work firmly in the skeptic camp, using all the right code words and signs.
A few select passages to illustrate:
This effort to reconstruct our planet’s climate history has become linked to the topic of Anthropogenic Global Warming (AGW). On the one hand, this is peculiar since paleoclimatological reconstructions can provide evidence only for the detection of AGW and even then they constitute only one such source of evidence.
The first sentence seems so self-evident to be rather sophomoric. Of course paleoclimate reconstructions are linked to the topic of AGW — duh! It’s climate. Climate change. Paleoclimate studies past climates and climate changes. The claim that this is peculiar makes no sense — of course we want evidence for the detection of AGW!
Who are these people?
On the other hand, the effort of world governments to pass legislation to cut carbon to pre-industrial levels cannot proceed without the consent of the governed and historical reconstructions from paleoclimatological models have indeed proven persuasive and effective at winning the hearts and minds of the populace. Consider Figure 1 which was featured prominently in the Intergovernmental Panel on Climate Change report (IPCC, 2001) in the summary for policy makers1 . The sharp upward slope of the graph in the late 20th century is visually striking, easy to comprehend, and likely to alarm.[my emphasis]
This reference to policy and “the consent of the governed” and the use of the code word “alarm” seems out of place in a technical paper in a stats journal. The authors could cut out the entire section here and it would not diminish the paper at all — in fact, including this detracts from the paper’s overall sense of objectivity. Perhaps this is commonplace in statistics journals and I am just misled. I somehow doubt it.
But it gets worse — this paper reads as an almost pure advocacy paper.
Quotations like the above and graphs like those in Figures 1, 2, and 3 are featured prominently not only in ofﬁcial documents like the IPCC report but also in widely viewed television programs (BBC, September 14, 2008), in ﬁlm (Gore, 2006), and in museum expositions (Rothstein, October 17, 2008), alarming both the populace and policy makers. [my emphasis]
Alarming policy makers? Reported widely in television programs? Museum expositions? Oh, the humanity! This reminds me of an episode of Conspiracy Theory with Jesse Ventura…
Wait — there’s even more…
The authors then provide a section on the controversies surrounding the hockey stick graph.
With so much at stake both ﬁnancially and ecologically, it is not surprising that these analyses have provoked several controversies. While much of this has recently erupted in the popular press (Jolis (November 18, 2009), Johnson (November 23, 2009), Johnson and Naik (November 24, 2009)), we root our discussion of these controversies in the history as it unfolded in the academic and scientiﬁc literature. [my emphasis]
Jolis, Johnson and Naik are all from The Wall Street Journal. Gee, the controversy was covered in a helluva lot more media outlets and forms than the WSJ. Of course, WSJ has also tended to take a skeptical approach to the issue of AGW, especially in the last year or so. The WSJ articles referenced are all pro-skeptic, focusing on Steve McIntyre and climategate. So much for situating the controversy historically and objectively…
I mean, if you’re going to delve into this, do it right and do it credibly.
Not only is the history of the controversy badly done, but the coverage of the scientific and statistical controversy and history is likewise inadequate and slanted towards the skeptic/contrarian side. It is also erroneous, as Deep Climate shows in his post on the paper.
Some of the language used is also highly suspect and not appropriate for a serious paper in a stats or science journal, at least in my view.
In his Congressional testimony (Wegman, 2006), committee chair Edward Wegman excoriated Mann et al. (2004)’s use of additional principal components beyond the ﬁrst after it was shown that their method led to spurious results…
This is a facile presentation of the Wegman hearing. There is no deeper analysis of Wegman and the investigation and it shows either a willful or real ignorance of the fact that along with so-called alarmism, there is also denialism. Even if one accepts that the graphic was used to alarm policy makers and the public — and I don’t — one should also recognize that the reverse can be true and some players can try to unreasonably dismiss evidence and downplay danger. An objective observer would provide analysis of both sides, those who overplay and overstate risks and certainties. I see no objectivity or balance in the presentation of the history and controversy in this paper.
Faced with a poor showing in the intro, one does lose confidence in the ability of the authors to be objective. However, it is entirely possible for the authors to get the history and controversy section wrong and they can be entirely right in their analysis of the technical issues. Even there they appear to get it wrong as other commenters along with Deep Climate point out.
When you calibrate, respectable Rabett’s want the largest spread of the variable calibrated against as possible. M&W calibrated proxies that respond to regional changes against the GLOBAL temperature record. If you look at Tamino’s figure, for about 80 of ~120 years (M&S only go to 2000, there ain’t a lot of proxies that go to 2010), a flat line is about the best description of what happened. This covers the period from ~1880 – 1920 and ~ 1940 – 1980. In such a situation, random noise is the best description of the variation. So especially if you hold out the last 30 years and prattle on about, bunnies find that random noise about a straight line provides the best fit, which is what the boys find, and of course it does not capture the sharp rise in the last 30 year period. As they say,
In other words, our model performs better when using highly autocorrelated noise rather than proxies to predict temperature. The real proxies are less predictive than our “fake” data.Since the proxies are affected by the local temperatures (and precipitation and some other things that are all local) and the local temperatures varied much more strongly than the global in most cases, and surely for those cases where the proxies vary strongly, this is kindergarten work. Trivially, this procedure underestimates the response of the proxies to the temperature over long periods and exaggerates the error projected back to the year dot. You are fitting noisy data to a straight line to find a slope? C’mon. QED
DCs basic critique:
McShane and Wyner’s background exposition of the scientific history of the “hockey stick” relies excessively on “grey” literature and is replete with errors, some of which appear to be have been introduced through a misreading of secondary sources, without direct consultation of the cited sources. And the authors’ claims concerning the performance of “null” proxies are clearly contradicted by findings in two key studies cited at length, Mann et al 2008 and Ammann and Wahl 2007.These contradictions are not even mentioned, let alone explained, by the authors.
In short, this is a deeply flawed study and if it were to be published as anything resembling the draft I have examined, that would certainly raise troubling questions about the peer review process at the Annals of Applied Statistics.
Martin Vermeer also provides a crit of the paper in comments at Deltoid:
The funny thing is that this paper actually replicates Mann et al. 2008 without even noticing it…
To partake in this dirty little secret, see their Figure 14 on page 30: the blue curve is wiggle-identical and practically a photocopy of Mann’s corresponding EIV NH land curve. As it should be. The higher (green) curve they canonize and which is shown above is the result of an error: they calibrate their proxies against hemispherical mean temperature, which is a poor measure of forced variability. The instrumental PC1 which the blue curve is based on, is a much better measure; its EOF contains the polar amplification effect. What it means is that high-latitude proxies, in order to be made representative for global temperatures, should be downweighted. The green curve fails to do this. Thus, high latitudes are overrepresented in this reconstruction, which is why the “shaft” is at such an angle, due to the Earth axis’s changing tilt effect on the latitudinal temperature dependence described in Kaufman et al. 2009.
The authors have no way of detecting such an error as their RMSE goodness-of-fit seems to be also based around the hemispherical average…
Here’s his concluding line:
While “How to Lie with Statistics” is famous, most statisticians do not lie, in my experience….
What might we find, examining that document:
1. Strive for relevance in statistical analyses. Typically, each study should be based on a competent understanding of the subject-matter issues…”
Zorita has a post up about the paper as well, that is worth a read. Zorita finds numerous errors and omissions and in general feels the paper lacked because the authors either didn’t read the papers they quoted or could have used some assistance from climate scientists.
In summary, admittedly climate scientist have produced in the past bad papers for not consulting professional statisticians. The McShane and Wyner paper is an example of the reverse situation.
So — a new attempt to demolish the hockey stick and from initial analysis, not so successful despite the high-fives and happy dancing over at WUWT, CA and other places.
The main criticisms of MBH98/99 and 08 can be summarized by the following: the “hockey stick” is a fabrication, created by improper methods and data:
- The use of a skewed or decentered PC
- The use of bad proxies such as the Stahle and NOAMER PC1 series
- The Gaspe series
- Bristlecone pines
- Tree rings are not good temperature proxies — divergence
- Overstating confidence in the findings of tree ring studies
All of these criticisms have been either addressed or refuted at blogs like RC and others.
Still, the skeptics/contrarians/denialists hold on tight to their mantras about the hockey stick being broken. They rushed to congratulate the authors and each other over this yet-unpublished paper before most of them probably even understood what it concluded or whether its conclusions were valid.