Readers may recall this posting A detailed review of Mann’s book: The Hockey Stick and the Climate Wars as it relates to the Wegman report to Congress. This post today is a continuation of that review, with more in-depth technical detail.
By Brandon Shollenberger
The Beginning
Earth Day, April 22, 1998, was the day the hockey stick was born. On that day, Michael Mann, and co-authors Ray Bradley and Malcolm Hughes published a paper in the scientific journal Nature (referred to as MBH98). This paper claimed to reconstruct northern hemispheric temperatures from the past 600 years by examining temperature “proxies” found in nature. The most important of these proxies were tree rings, the size (and density) of which can be influenced by temperatures.
The results of this paper were dramatic. The temperature reconstruction it contained showed relatively flat temperatures for approximately 500 years followed by a sharp increase in temperatures over the last hundred years. The sharp increase formed a curve, which when attached to the end of a relatively flat line created the image of a “hockey stick.” It told the viewer current temperatures were higher than anything seen in hundreds of years. Looking at it, it was almost impossible to think anything other than, “Humans are causing a dramatic change in temperature.”
Not only was the resulting image powerful, it was also extremely definitive. MBH98 claimed modern warmth was unprecedented in 600 years with “roughly a 99.7% level of certainty.” This high degree of confidence was only reinforced by the paper saying it’s conclusions weren’t based on a single type of proxy (such as tree rings), but rather:
the long-term trend in NH is relatively robust to the inclusion of dendroclimatic indicators in the network, suggesting that potential tree growth trend biases are not influential in the multiproxy climate reconstructions.
The authors said their conclusions were almost absolutely certain. They said their results were so certain, you could throw out tree ring data (dendroclimatic indicators), their largest source of data, and they’d still get the same results. The authors were full of it. On page 51 of Michael Mann’s book, he discusses an analysis he performed shortly after MBH98 was published:
The tests revealed that not all of the records were playing an equal role in our reconstructions. Certain proxy data appeared to be of critical importance in establishing the reliability of the reconstruction–in particular, one set of tree ring records spanning the boreal tree line of North America published by dendroclimatologists Gordon Jacoby and Rosanne D’Arrigo.
If “one set of tree ring records” was “of critical importance in establishing the reliability of the reconstruction,” the reconstruction could not have been “relatively robust to the inclusion of dendroclimatic indicators.” While Mann now casually admits the importance of such a small amount of data, neither he nor his co-authors ever made any effort to correct their paper on the point.
The next year, these authors published a new paper (MBH99), extending their hockey stick back another 400 years. In it, they concluded:
The 1990s was the warmest decade [of the last millennium], and 1998 the warmest year, at moderately high levels of confidence.
These two papers, collectively referred to as MBH, formed the basis for what is the most memorable image used in discussions of global warming. In 2000, Bill Clinton referenced it in his State of the Union Address. More importantly, in 2001, the International Panel on Climate Change (IPCC), an organization created by the United Nations to periodically release “assessments” of the state of knowledge on global warming, gave it prominent display. A summary made for government officials of its Third Assessment Report (TAR) even used MBH to conclude it likely “the 1990s has been the warmest decade and 1998 the warmest year of the millennium.” Out of hundreds of pages of documents, this image was selected to be the “public face” of global warming.
Controversy
Controversy began when Stephen McIntyre and Ross McKitrick collaborated on a paper published in the journal Energy & Environment in 2003. They concluded:
The particular “hockey stick” shape… is primarily an artefact of poor data handling, obsolete data and incorrect calculation of principal components.
In response to this conclusion, Mann fabricated a story about McIntyre and McKitrick’s results being based upon a faulty spreadsheet. However, he also said (page 123):
The paper’s dramatically different result from ours… was instead an artifact of the authors’ having inexplicably removed from our network two-thirds of the proxy data we had used for the critical fifteenth-sixteenth century period.46
This is untrue. McIntyre and McKitrick were forced to omit some data (but not two-thirds) because they couldn’t figure out certain undisclosed methodological choices Mann had made. When McIntyre asked Mann to disclose what he had done, Mann refused. Because it was impossible to know what Mann had actually done, McIntyre simply emulated the process as best he could. Despite what Mann claims, the difference in methodology didn’t affect any conclusions.
Peculiarly, the reference Mann gives says nothing about this claim. It says McIntyre and McKitrick were wrong, but gives totally different reasons.
This is especially strange as Mann wrote the article he references.
The Follow-Up
In this book, I attempt to tell the real story behind the hockey stick.
Michael Mann – Prologue
Over the next two years, both “sides” of the controversy tried to support their position. Most notably, Mann was forced to publish a corrigendum by Nature in order to correct errors pointed out in his work, though he claimed, “None of these errors affect our previously published results.”
During this period, Mann and some of his colleagues started a blog, RealClimate. McIntyre started a blog of his own, ClimateAudit, to respond to things posted on RealClimate. Many discussions and arguments were made on these two web sites, eventually leading McIntyre and McKitrick to publish another paper in the journal Geophysical Research Letters (GRL). Mann says of it (page 130):
McIntyre and McKitrick had quietly dropped their erroneous original assertion (in their 2003 paper discussed in chapter 8 that the hockey stick was an artifact of bad data. Their new, albeit equally erroneous, assertion was that the hockey stick was an artifact of the conventions used in applying principal component analysis (PCA) to certain tree ring networks…
While Mann claims the argument by McIntyre and McKitrick was new, it was one they had made in their first paper. The abstract of that paper states (emphasis added):
The particular “hockey stick” shape… is primarily an artefact of poor data handling, obsolete data and incorrect calculation of principal components.
This fact is even acknowledged by Mann in his book (emphasis added – note #45)
To be specific, they claimed that the hockey stick was an artifact of four supposed “categories of errors”: “collation errors,” “unjustified truncation and extrapolation,” “obsolete data,” and “calculation mistakes.”
McIntyre and McKitrick had always been aware there was a problem with how Mann did PC calculations, so this was not a “new” issue. All that was new was McIntyre and McKitrick had realized the data errors they had found were mostly irrelevant to the MBH results. Having realized that, they began to focus more on the main issue, the PC calculations. In regard to this, Mann says (page 137):
McIntyre and McKitrick used a different PCA convention in their 2005 paper. They centered the tree ring data over the long term (1400—1980). That’s fine—in fact, long-term centering is actually the traditional convention…
Clearly, Mann does not think they calculated their PCs incorrectly. Instead, he claims:
Applying our selection rule to these data, using a modern centering convention indicated that the leading two PC series should be retained…. By misapplying a selection rule derived for one convention (modern centering) to PCA results based on a different convention (long-term centering) [they] end up erroneously throwing out the proverbial baby with the bathwater.
Both groups kept two PCs for the North America tree ring network (NOAMER). Mann claims this is wrong, that McIntyre and McKitrick should have kept more. This fairly simple claim is Mann’s basis for dismissing the GRL paper:
In effect, McIntyre and McKitrick had “buried” or “hidden” the hockey stick. They had chosen to throw out a critical pattern in the data as if it were noise
In their GRL paper, McIntyre and McKitrick never said anything about how many PCs to keep. Instead, the paper is a discussion about how PCs were calculated with NOAMER being used as an example. Given Mann’s claim has no possible connection to this paper, it’s natural to try looking at another paper published by McIntyre and McKitrick that year. That paper was published in Energy and Environment (EE), and it did discuss how many PCs get kept:
If a centered PC calculation on the North American network is carried out (as we advocate), then MM-type results occur if the first 2 NOAMER PCs are used in the AD1400 network (the number as used in MBH98), while MBH-type results occur if the NOAMER network is expanded to 5 PCs in the AD1400 segment (as proposed in Mann et al., 2004b, 2004d). Specifically, MBH-type results occur as long as the PC4 is retained, while MM-type results occur in any combination which excludes the PC4. Hence their conclusion about the uniqueness of the late 20th century climate hinges on the inclusion of a low-order PC series that only accounts for 8 percent of the variance of one proxy roster.
Rather than simply “throw out” data based upon a “selection rule,” McIntyre and McKitrick carefully considered what happens based on how much data is used. Mann’s claim is exactly the opposite of the truth in relation to the EE paper (and is completely nonsensical in relation to the GRL paper). He continues this sort of misrepresentation (page 136):
We employed a standard, objective criterion for determining how many PCs should be kept for each region.
In the note he provides, he says the rule he used is called Preisendorfer’s Rule N. There is no evidence this rule was actually used on the tree ring networks. This claim first appeared years after the hockey stick was made, it wasn’t supported by any of the program code released my Mann, and the evidence says it couldn’t have been used.
Mann Seeks Support
During any controversy, people are bound to join in on the arguments. The hockey stick controversy is no different. Mann refers to one example of this when he discusses work by Eugene Wahl and Caspar Ammann (page 138):
Wahl and Ammann demonstrated that the hockey stick was not an artifact of PCA conventions and that the basic result is robust as long as key proxy records are not thrown out (either explicitly as in the original 2003 McIntyre and McKitrick paper, or implicitly through the use of erroneous selection rules, as in their 2005 paper).
Again, Mann repeats his misrepresentations of McIntyre and McKitrick’s work. More importantly, he says Wahl and Ammann find the MBH “result is robust as long as key proxy records are not thrown out.” This is the exact result observed by McIntyre and McKitrick. It is the exact result Mann admits in his book. Everyone agrees if you keep that particular set of tree ring records, you get a hockey stick. If you remove it, you don’t get a hockey stick.
Mann goes on to say Wahl and Ammann:
showed that, had McIntyre and McKitrick subjected their alternative reconstruction to the statistical validation tests stressed in MBH98 and MBH99 (and nearly all related studies), it would have failed these critical tests.
This is problematic in a number of ways. First, McIntyre and McKitrick never claimed to be offering an “alternative reconstruction.” They were merely testing what happened if certain changes were made. This serves the same purpose as running statistical validation tests. Both are ways of seeing how robust a paper’s results are.
Second, Mann raises the issue of statistical validation tests. There are a variety of such tests, the two most important of which are RE and r2. The closer the results of these tests are to one, the better the conclusion is. The problem is McIntyre had long criticized Mann for not publishing r2 verification scores which were practically 0 (very bad). Mann calculated these scores, but he never published the adverse results. When a committee formed by the United States House of Representatives asked Mann:
Did you calculate the R2 statistic for the temperature reconstruction, particularly for the 15th Century proxy record calculations and what were the results?
Mann simply avoided answering the question:
I assume that what is meant by the “R2” statistic is the squared Pearson dot-moment correlation, or r2 (i.e., the square of the simple linear correlation coefficient between two time series) over the 1856-1901 “verification” interval for our reconstruction. My colleagues and I did not rely on this statistic in our assessments of “skill”
He doesn’t admit or deny calculating the scores. He simply says he and his coauthors didn’t “rely” upon them. Whether or not they relied upon the scores, those scores are obviously relevant to anyone looking at the hockey stick. It would especially have been relevant to the IPCC which claimed Mann and co-authors (emphasis added):
estimated the Northern Hemisphere mean temperature back to AD 1400, a reconstruction which had significant skill in independent cross-validation tests.
Even worse, while the adverse results were hidden, Mann and his co-authors published r2 scores when they were helpful. Figure 3 of MBH98 shows r2 scores:
Figure 3 shows the spatial patterns of calibration b, and verification b and the squared correlation statistic r2, demonstrating highly significant reconstructive skill over widespread regions of the reconstructed spatial domain.
Given all this, it is difficult to understand why Mann would bring up statistical validation tests. He has long hidden the fact his own work fails such tests, and there is no reason failing such tests would matter for McIntyre and McKitrick’s results (they weren’t doing an alternative reconstruction).
To add to the oddness, Wahl and Ammann actually show the failing MBH r2 scores.
Congress
A second flood, a simple famine, plagues of locusts everywhere
Or a cataclysmic earthquake, I’d accept with some despair
But, no, you sent us Congress, good God, sir, was that fair?
Piddle, Twiddle and Resolve – 1776 (musical)
By this point, the United States Congress had already gotten involved in the hockey stick debate. In 2006, it increased its involvement by commissioning two reports to study the controversy, the National Academy of Science (NAS) Report and the Wegman Report.
The most important conclusion given by both of these reports deals with a methodological choice made by Mann involving principal component analysis (PCA). Mann used a non-standard implementation of PCA. His critics claimed this caused his method to “mine” for hockey sticks. If true, it would mean Mann’s methodology inherently gave undue influence to that particular shape. Both reports acknowledged this criticism. The NAS Report said:
As part of their statistical methods, Mann et al. used a type of principal component analysis that tends to bias the shape of the reconstructions.
The Wegman Report said:
The net effect of this decentering using the proxy data in MBH98 and MBH99 is to produce a “hockey stick” shape.
Both reports agree the original hockey stick was created by a biased methodology. It sought hockey sticks in the data and gave them undue significance. Despite this, Mann says (page 164):
The more extensive and authoritative NAS review, for example, had specifically dismissed the notion that PCA conventions had any substantial impact on our findings. As Bloomfield had put it at the NAS press conference, “the committee, while finding that the issues are real, [found] they had a minimal effect on the final reconstruction.”
Rather than quote the NAS Report, Mann quotes a comment made in a press conference which isn’t supported by the report. He does quote the report on page 161:
The basic conclusion of Mann et al. (1998, 1999) that the late 20th century warmth in the Northern Hemisphere was unprecedented during at least the last 1,000 years has subsequently been supported by an array of evidence that includes both additional large-scale surface temperature reconstructions and pronounced changes in a variety of local proxy indicators
However, this merely supports the conclusion of MBH, not the methodology. Indeed, nothing in the NAS Report actually supports Mann’s work. Instead, it merely says other work reached the same conclusions. This cannot possibly address the merits of Mann’s work, a point expressed by Edward Wegman (the lead author of the report bearing his name):
Method Wrong + Answer Correct = Bad Science.
Despite this, Mann says:
The NAS report was widely reported to be an affirmation of our work.
Projection
Mann flagrantly misrepresents the NAS report in regards to “bristlecones,” the type of tree the all-important tree ring data was taken from. Mann says of it (emphasis added – page 190):
McIntyre also appealed to the conclusions of the 2006 NAS report to claim that our continued use of the very long bristlecone pine series was inappropriate. Yet this was a misrepresentation of what the NAS had concluded. The NAS panel expressed some concerns about so-called strip-bark tree ring records, which include many of the long-lived bristlecone pines. These trees grow at very high CO2-limited elevations, and there is the possibility that increases in growth over the past two centuries may not be driven entirely by climate, but also by the phenomenon of CO2 fertilization – something that had been called attention to and dealt with in MBH99 (see chapter 4). The NAS report simply recommended efforts to better understand any potential biases by “performing experimental studies on biophysical relationships between temperature and tree-ring parameters”.
This is a gross misrepresentation of the NAS report’s findings. From the very same page as the quote he offers (strip-bark is the type of bristlecones being discussed – page 52):
While “strip-bark” samples should be avoided for temperature reconstructions, attention should also be paid to the confounding effects of anthropogenic nitrogen deposition (Vitousek et al. 1997)…
McIntyre cited a conclusion from the very same page Mann was quoting from, yet Mann claims it was a misrepresentation. Clearly, the reverse is true. More importantly, it is clear bristlecones are a questionable data source. The NAS Report states this. It also acknowledges Mann’s hockey stick was dependent upon bristlecones:
For periods prior to the 16th century, the Mann et al. (1999) reconstruction that uses this particular principal component analysis technique is strongly dependent on data from the Great Basin region in the western United States.
There’s a final oddity to this issue. In a RealClimate post, Mann’s co-author Ray Bradley said:
One final note: bristlecone pines often have an unusual growth form known as “strip bark morphology” in which annual growth layers are restricted to only parts of a tree’s circumference. Some studies have suggested that such trees be avoided for paleoclimatic purposes, a point repeated in a recent National Academy of Sciences report (Surface temperature reconstructions for the last 2,000 years. NRC, 2006).
Mann even commented on that blog post (inline response to comment #7), yet he now completely misrepresents the finding his co-author referred to in it.
His treatment of the Wegman Report is little better (page 164):
The Wegman Report, commissioned by Joe Barton and published several weeks after the NAS report, seemed a transparent effort to further spread the attacks against our work. It uncritically repeated the old and tired McIntyre and McKitrick claim that the hockey stick was an artifact of the conventions used in a statistical (PCA) analysis…
The most important fact about the Wegman Report is not actually found in the Wegman Report. Instead, it was stated by Gerald North, the chair of the panel which wrote the NAS report:
CHAIRMAN BARTON. I understand that. It looks like my time is expired, so I want to ask one more question. Dr. North, do you dispute the conclusions or the methodology of Dr. Wegman’s report?
DR. NORTH. No, we don’t. We don’t disagree with their criticism. In fact, pretty much the same thing is said in our report.
The same point was reiterated by another member of the panel, Peter Bloomfield:
MR. BLOOMFIELD. Thank you. Yes, Peter Bloomfield. Our committee reviewed the methodology used by Dr. Mann and his coworkers and we felt that some of the choices they made were inappropriate. We had much the same misgivings about his work that was documented at much greater length by Dr. Wegman.
Mann claims the Wegman Report was just a repetition of McIntyre and McKitrick’s arguments. The NAS panel agreed with the criticisms found in the Wegman Report…
The Hockey Stick, Redux
“Second verse, same as the first!”
I’m Henery the Eighth, I Am(song)
In 2008, Mann published a new hockey stick. Mann describes it (page 190):
With far more ice core and sediment records now available, we were able to obtain a meaningful reconstruction of the Northern Hemisphere average temperature for the past thirteen hundred years without using tree ring data at all. If tree ring data were used, the reconstruction could be extended, with some reservations, back over the past seventeen hundred years.
Mann’s critics claimed his original hockey stick was purely a product of a small amount of tree ring data. If his new reconstruction was free from that problem, it would be a major development. However, McIntyre almost immediately claimed to find problems with the new reconstruction:
Stephen McIntyre wasted little time in launching a series of attacks on the PNAS paper, employing–it would seem– the strategy of throwing as much mud against the wall as possible and hoping that some would stick. Teaming up with his former coauthor Ross McKitrick, he submitted a short letter to the editor of PNAS claiming that our reconstruction used “upside down proxy data.”52 That was nonsensical, as we pointed out in our response,53 one of our methods didn’t assume any orientation, while the other used an objective procedure for determining it.54
As Mann explains, two different methodologies were used, Composite Plus Scale (CPS) and Error-in-Variables (EIV). However, there is nothing “nonsensical” about saying data was used upside down. The CPS methodology screens proxy records by directly comparing them to the local instrumental records. If the two records are similar enough, the proxy record gets used. The problem is proxy records can increase without meaning temperatures increased. If one were measuring the accumulation of snow/ice, larger values would be expected for cooling, not warming. This increase would be compared to an increase in instrumental temperatures, and thus the CPS methodology would treat the cooling as warming. This would cause the series to be used upside down.
EIV is similar to this, though it doesn’t screen proxy series. Instead, it compares each proxy series to the temperature record and determines how similar the two are. If it finds a similar trend, but in the opposite direction, it “flips” the series upside down. This means both methodologies used by Mann are capable of using proxy series upside down despite the fact he claims such is “nonsensical.”
McIntyre settled then on a more specific avenue of attack: our use of a small group of sediment records from Lake Korttajarvi in central Finland. But this was quite inconsequential and, ironically, we were the ones who had raised concerns about these particular data in the first place, not McIntyre. We had included them for consideration only to be complete in our survey of proxy records in the public domain.
The records Mann is referring to here are commonly called the Tiljander series. The four series are labeled Thickness, Lightsum, Darksum and XRD. Thickness and XRD are measured, but Lightsum and Darksum are derived from those measurements. This means using using all four series, which Mann did, results in double counting.
More importantly, these series were corrupted by human influence. The lake they were taken from began being influenced by farming and construction tn the 1700s. The impact from human influence completely overwhelmed any temperature signal there may have been in the data. The people who originally published the series noted this and cautioned people not to use the modern portion of the series as a temperature proxy.
Since Mann’s methodologies require calibrating proxy series to the instrumental record (1850-1995). it makes no sense to use series whose data has been corrupted in the modern periods. Any correlation which may be found is spurious, not caused by the proxy actually responding to temperature. Since the correlation is spurious, it could not have any connection to the temperature response the series were supposed to have before being corrupted. This is what caused two of the Tiljander series to be used with the opposite correlation as that suggested by the original authors.
Mann’s Nonsense
In the online supplementary information accompanying publication of our PNAS article, we had both noted the potential problems with these records and showed that eliminating them made absolutely no difference to the resulting reconstruction.57 McIntyre had thus attempted to fabricate yet another false controversy
Mann acknowledged the authors warning not to use the data as he did, yet used it anyway. The reasoning he offers for such makes no sense: he says there is “no difference” if he uses the series. If there is no difference, why include them? The answer is simple. Using them makes a huge difference.
The main temperature reconstruction is barely affected by removing the Tiljander series because it includes the tree-ring data which was essential for Mann’s original hockey stick. Mann’s paper claims not to need that data to get a hockey stick, but that is only true if he includes the Tiljander series. If you remove both the Tiljander and tree ring series, there is no longer a hockey stick.
This point is confirmed by Gavin Schmidt, a coauthor of Mann’s at RealClimate:
Since the no-dendro CPS version only validates until 1500 AD (Mann et al (2008) ), it is hardly likely that the no-dendro/no-Tilj CPS version will validate any further back, so criticising how bad the 1000 AD network is using CPS is hardly germane. Note too that while the EIV no-dendro version does validate to 1000 AD, the no-dendro/no-Tilj only works going back to 1500 AD (Mann et al, 2009, SI).
A commenter at RealClimate noticed this remark and asked:
So just to be clear with regard to your response to 525. Under either method (CPS or EIV) it is not possible to get a validated reconstruction to before 1500 without the use of tree rings, or the Tiljander sediments.
Schmidt responded:
That appears to be the case with the Mann et al 2008 network.
Mann himself has acknowledged this. From the Supplementary Information for a later paper:
Additional significance tests that we have performed indicate that the NH land+ocean Had reconstruction with all tree-ring data and 7 potential “problem” proxies removed (see original Supp Info where this reconstruction is shown) yields a reconstruction that passes RE at just below the 95% level (approximately 94% level) back to AD 1300 and the 90% level back to AD 1100 (they pass CE at similar respective levels).
The test used by Mann required his reconstruction pass at a 95% confidence level, and he acknowledges it can only do so by including either the tree ring data or the (nonsensically used) Tiljander series. The “false controversy” he claims McIntyre raised actually repudiates a central claim of Mann’s paper:
With far more ice core and sediment records now available, we were able to obtain a meaningful reconstruction of the Northern Hemisphere average temperature for the past thirteen hundred years without using tree ring data at all.
Nobody Agrees With Mann
Mann continues to spread disinformation (page 198):
When Science in early September 2009 published an article by Darrell Kaufman and his colleagues showing the most dramatic hockey stick yet–a two-thousand-year reconstruction of Arctic temperature changes19–Stephen McIntyre and his forces went on the attack on the Internet,20 immediately trumpeting the false claim that the work was compromised by bad data, despite the fact that whether or not the authors used the data in question made no difference to the result they obtained.
The “data in question” are the Tiljander series which were once again used upside down. Despite Mann’s claims, McIntyre never said this was the source of the Kaufman hockey stick (he primarily blamed another series, Yamal). Beyond that, a few months after the Kaufman paper came out, a corrigendum was published. Included in it was this line:
Record 20 was corrected to reflect the original interpretation of Tiljander et al. (S32) that X-ray density is related inversely to temperature.
Mann claims McIntyre raised a “false claim” to attack a paper, yet the authors of that paper acknowledged his claim was correct. Even stranger, Ray Bradley was a coauthor on both Mann’s 2008 paper and the Kaufman paper. Both papers made the same mistake, but only the Kaufman group admitted it.
A Simple Point
For all the “technical” issues in Mann’s papers, the controversy is actually very simple. Mann’s papers give undue focus to a small amount of data. Even he and his supporters admit his original hockey stick was based entirely upon a small amount of tree ring data (which the NAS says should not be used to measure temperature). His latest hockey stick was the same, save he added upside down data which he couldn’t possibly calibrate to temperature.
Denouement
“If you want a happy ending, that depends, of course, on where you stop your story.”
Orson Welles
One of the most common defenses offered for Mann’s hockey stick is other papers get the same result. The idea is if Mann got the right answer, criticisms of his work don’t matter. This is a dumbfounding position, and the best response is that given above by Wegman:
Method Wrong + Answer Correct = Bad Science.
Mann’s work has been highly publicized. If the glaring problems in it are overlooked, how can anyone trust other papers reaching the same conclusions? What is to stop those other papers from being just as flawed? Nothing. They cannot be ignored or dismissed because of flaws in Mann’s work, but they should all be carefully examined rather than accepted on faith. Unfortunately, the same basic criticisms are leveled against practically every one of those reconstructions.
General Issues
It would be impossible to discuss every paper showing a hockey stick. However, two general problems found in them can be covered. The first problem has already been shown, namely, mistakes don’t get admitted. Mann’s PC1 (the source of his hockey stick) was created with a biased methodology, and it was made up of data the National Academy of Scientists said should be avoided. Despite this, it was included in the latest IPCC report.
Related to the above, papers with hockey sticks tend to rely on the same data. In addition to bristlecones, a commonly used series is called Yamal. Mann discusses it (page 198):
A more vicious attack was reserved for later that month. The matter concerned a tree ring temperature reconstruction for Russia’s Yamal region that Keith Briffa and colleagues had published some years earlier; it once again showed recent warmth to be anomalous in a two-thousand-year context. At a time when Briffa was known to be seriously ill and not in a position to respond to any allegations, McIntyre publicly accused him of having intentionally cherry-picked tree ring records to get a particular result…
To support his “cherry picking” allegation, McIntyre had produced his own composite reconstruction–which happened to lack the prominent recent warming evident in Briffa’s reconstruction.
McIntyre didn’t accuse Briffa of cherry-picking, and he didn’t make “his own… reconstruction.” He simply did a sensitivity test. Testing to see what happens when you make a change is not the same as saying that change is “right.”
How did he accomplish this? By deleting tree ring records of Briffa’s he didn’t seem to like, and replacing them with other tree ring data he had found on the Internet, which were inappropriate for use in a long-term temperature reconstruction
Mann claims the data added was “inappropriate for use in a long-term temperature reconstruction,” but it was no different than the data McIntyre removed. Mann also claims the data was “data he had found on the Internet.” Surprisingly, that’s true. McIntyre found the data on the internet web page for the International Tree Ring Data Bank, the single largest repository for tree ring records… As for the “tree ring records… he didn’t seem to like,” they were 12 cores (tree rings measurements), a rather low amount. McIntyre removed them to see what would happen if a different site’s data was used instead. This new site had 34 cores, a far better number, and it was from the same area. More importantly, McIntyre then added the 12 cores back in and got the same result.
Put simply, McIntyre showed a series with a prominent hockey stick lost it’s hockey stick shape if a little data from the same area was added. This series has been used in a dozen reconstructions. Is it any surprise those reconstructions got the same result as Mann got? All this shows is if you give a small amount of questionable data undue focus, you can get the same results Mann got by giving a small amount of questionable data undue focus.
The hockey stick was originally accepted without anyone verifying it. That was a mistake. Newer hockey sticks were accepted without anyone verifying them. That was a mistake. Will the same mistake be made with Mann’s book?
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“Please supply more information. -REP]”
Could I know the name of who “REP” is?
[REPLY: Sorry, no. I trust you are not objecting to efforts to keep the tone of WUWT above that of certain other sites which shall remain namless? Engage the greenies. It’s a target rich environment. -REP]
To learn about William Connolley you could start here:
http://wattsupwiththat.com/2009/12/19/wikibullies-at-work-the-national-post-exposes-broad-trust-issues-over-wikipedia-climate-information/
The reason I ask for the name of “REP” is because I figure he/she must be new to the work here to not know about this post.
[REPLY: Not that new, but every once in awhile the Irish Alzheimer’s kicks in: we forget everything but the grudges. Thanks for pointing to the link. -REP]
Peter Kovachev;
PS: Re your questions for Connolley (March 11, 2012 at 5:34 pm), allow me to supply a proxy response on his behalf: Read The Documents and go to ScepticalScience Blog. Better to hear it from a friend.>>>>
Ah, well, then am I allowed a proxy rebuttal?
Mr. Connolley, on the proviso that you were about to respond to me along the lines suggested by Mr. Kovachev, may I please advise:
o I have read the documents already
o I have visited scepticalscience blog many times
Now, may I please have answers to the questions that I asked?
PREDICTION – Mr Connolley will not respond to my questions with direct answers for the simple reason that he has no credible answers to supply. He will either respond with misdirection and obfuscation, or ignore me altogether.
Ted G makes a valid point concerning the political mind set of those who support the very political non-scientist Mann and his mendacious book. Paul Ehrlich, who, believe it or not, has made more false predictions of disaster, and is a mentor to Obama’s political czar John Holdren.
You cannot talk about sustainability without talking about people, about politics, about power and control.” John Holdren* A more honest definition I have yet to read- He who controls the sustainable definition- controls the power and the people.
*from a 1995 World Bank speech-The Meaning of Sustainability: Biogeophysical Aspects by John P. Holdren, Gretchen C. Daily, and Paul R. Ehrlich
”Giving society cheap, abundant energy would be the equivalent of giving an idiot child a machine gun.”
Paul Ehrlich,
Professor of Population Studies,
Author: “Population Bomb”, “Ecoscience
”A massive campaign must be launched to de-develop the United States. De-Development means bringing our economic system into line with the realities of ecology and the world resource situation.”
Paul Ehrlich,
Professor of Population Studies,
Author: “Population Bomb”, “Ecoscience”
”If I were reincarnated I would wish to return to earth as a killer virus to lower human population levels.”
Prince Phillip, Duke of Edinburgh,
husband of Queen Elizabeth II,
Patron of the Patron of the World Wildlife Foundation
”The big threat to the planet is people: there are too many, doing too well economically and burning too much oil.”
Sir James Lovelock,
BBC Interview
A cruel crowd of failed, but well paid, profits of ever impending doom.
we forget everything but the grudges….
LOL
Pat Frank;
Do you really want to wreck the huge majority honest to get at the minority corrupt, or is some rational discrimination preferable?>>>
Pat, I did not read Gail’s “prescription” but… yes. Rational discrimination is, history tells us, not possible. The corrupt minority seize power, and once they have it, they will not relinquish it lightly. For anyone who follows the climate debate with any kind of serious effort, this is precisely what has happened, and the damage to the global economy is staggering. Real people are really starving because we’re burning the food in the name of protecting the ecosystem to keep them from starving.
Government should be regulator and watchdog. The moment that government steps into the arena of “real work”, corruption follows.
Given that tree growth is typically parabolic in response to temperature, how do you know a priori which side of the maximum you might be on when attempting a reconstruction?
Thanks for the endorsement, Hu.
Getting a thumbs up from you is high praise indeed.
Rob Tamaki
harry says:
March 11, 2012 at 5:05 pm
William Connelly wrote:
Having used the instrumental record as a way of selecting “appropriate” trees, it is rather confused logic to claim that the instrumental record verifies the usefulness of tree proxies.
The correct statement is “usefulness of tree proxies in obtaining political influence and continued funding”.
The mistake is to assume that this has anything to do with temperature. The Judas’s of the world will earn their 40 pieces of silver, the Kings will rule and the public will be crucified, all in the name of salvation.
davidmhoffer,
I concur. I was thinking of running a simple non-linear model of complex processes or our Prof Scafetta’s Diffusion Entropy Analysis to decide whether Connolley will either a) try to wing a short and glib response perhaps even with the assistance of the Suzuki Fruit Fly or, b) ignore your questions by splitting for a few days. I went for the ignoring hypothesis. I’d keep a copy of those great questions handy for when he next makes his appearance, though. Imagine plotting the freaky hockey stick line of his anxiety levels as you chase him all over the blog with that bundle of pain. Hours of wholesome entertainment for the entire family. Great for home, school or the office, as they say.
I suppose there had to be someone out there – William Connolley – who believes:
1. Tree rings are an accurate proxy for historic temperatures – they are of course, but only if you filter out all the trees (the other 99%) which don’t provide you with the results required to demonstrate your model is correct.
2. The Hockey Stick is an accurate reflection of historic global temperature – it is of course, but only if you splice together different time series, ignore inconvenient facts and cherry pick the data.
3. Michael Mann is an honourable scientist – he is of course, but only by the abysmal standards of the ‘climate science’ industry, which would not be tolerated in any real field of science.
davidmhoffer says:
March 11, 2012 at 9:03 pm
PREDICTION – Mr Connolley will not respond to my questions with direct answers for the simple reason that he has no credible answers to supply. He will either respond with misdirection and obfuscation, or ignore me altogether.
=======================================
lol, given his lame responses to those of us that asked about determining the annual temps from a 2 month window, I’d say he’s best off simply ignoring.
Rob Tamaki,
Hu’s post led me to check out your Amazon review. I nearly dropped my cup of tea when you pointed out that “the name ‘Montford’ does not appear anywhere in Mann’s book – not in the main body, not in the footnotes, and not in the index.” What the…? To actually ignore even a mention in passing the main critique of one’s life’s work? Tells us a lot about about Mann the man, although not whether this glaring omission is a mark of juvenile churlishness, incomprehensible stupidity or the white feather mark of the cowering poltroon. I chortled through your enjoyable review, which not only a slam-dunked Mann’s book into the trash bin…very politely and even respectfully, though… but flogged a brazen endorsement of Montford’s Hockey Stick Illusion! LOL, what hutzbah you have, Sir! Bravo, I love it!
Go check out Rob’s nail in the coffin, everyone: http://www.amazon.com/Hockey-Stick-Climate-Wars-ebook/product-reviews/B0072N4U6S/ref=cm_cr_dp_all_summary?ie=UTF8&showViewpoints=1&sortBy=bySubmissionDateDescending
Frank O’Dwyer is doing a detailed job of demonstrating an embarrassing litany of errors in Shollenberger’s ‘review’. Shollenberger misunderstands a lot of what he reads. Probably due to bias…
http://frankodwyer.com/blog/2012/03/11/yet-more-shollenberger/
For something like five years now I’ve argued with fellows who like to insist that Mann’s work has been replicated by other scientists, and also verified by using different proxies. I feel the “other scientists” really should wear a badge of dishonor for contributing to a fraud. They should have known better.
To switch from tree-ring proxies to lake-sediment proxies in the manner that Mann did is a bit like getting caught red handed not once, but twice.
It is as if, once the Piltdown skull was shown to be a human cranium with an orangutan jaw, someone switched the orangutan jaw with a chimpanzee jaw, and said, “There! Now do you believe me?”
markx hits the nail on the head when he says,
(on March 11, 2012 at 11:40 am,)
“……I believe the only thing that has kept his career afloat until now is his incredible ability to write in the most advanced form of scientific obfuscatory phrasing. I guess he figured if it remains relatively incomprehensible, there is less chance he will be queried on it.”
The people who I’ve argued with for five years are in awe of Mann’s gobble-de-gook . Mann could say, “Flibblebot zimmerzee on the quockertop approach to cuttlesnark,” and they would nod, because they don’t want to look like they don’t understand.
Of course, to a true statistician like McIntyre, there is no such awe. What amazes me is that McIntyre has managed to be so polite, all these years.
Test. Did my last comment wind up in the spam bin?
By the way, Connolley’s skill can be tested. Just give him the June and July temperatures for various places, and ask him to produce the Spring, Winter and Fall temperatures. No need to involve tree-rings at all. Let him put his money where his mouth is.
Gillian:
At March 12, 2012 at 12:29 am you write:
“Frank O’Dwyer is doing a detailed job of demonstrating an embarrassing litany of errors in Shollenberger’s ‘review’. Shollenberger misunderstands a lot of what he reads. Probably due to bias…”
Thankyou, I do enjoy a good joke. I suppose you laughed writing it, and I laughed reading it, but it is not quite as funny as Connolly’s contributions.
You state no error in Shollenberger’s polite and accurate review but say we must trust that the masterful Frank O’Dwyer has found and will find some.
And you link to a site where O’Dwyer demonstrates his genius. His first assertion in that link is “Incorrect claim that Mann misrepresents Roy Spencer”. I read that longwinded diatribe and it proves Mann DID misrepresent Spencer: so, I did not bother to read more of the link.
I appreciate your joke in pretending there is a reasonable defence of Mann by attacking his critics.
And I appreciate the jokes of pretending Mann is reputable, is honest, and is a scientist. But any joke loses its effect when taken too far.
Richard
Amino Acids in Meteorites on March 11, 2012 at 8:09 pm:
From Amino Acids in Meteorites on March 11, 2012 at 8:49 pm
The link to the National Post blogs in the first paragraph and the one to “The Opinionator” also at the National Post blogs, linking to pieces by Lawrence Solomon, have gone 404.
Heartland pegged him as a “Green Party activist” in 2010 here, and linked to two Lawrence Solomon National Post pieces reposted at probeinternational.org. Those links report a strange “parse error” in the php code, the pieces are unavailable. Solomon used the same links here in a 2010 short piece that does not refer to Connolley as an activist, Green or otherwise.
But the Wayback Machine has the first piece, from 2008, here. Relevant part:
This is confirmed in Connolley’s Wikipedia entry (given reference directly linked by me):
Reference says:
From their “People” list, giving his policy specialty:
The Wayback Machine also has the second piece here but that has more examples of Connolley’s Wiki-bullying without referring to Green activism by Connolley, although the noted petty serial denying by Connolley of published established facts is humorous to read and indicative of activism.
The two mentioned 404 links in the WUWT piece are not findable by the Wayback Machine as the National Post has disabled web crawling by using the robots.txt protocol thus their pages are not archived. However, for any moderators that wish to update the links, the first piece is now here at the NP.
Google did find a copy of the second one saved here, a better one is here. I have been unable to locate a more “official” copy of this older May 2008 post.
He is in the Green Party, has engaged in activism. Indeed, one would have to be willfully ignorant to not acknowledge his Wiki-bullying as partisan activism. His Wikipedia User page says, presumably self-selected, take it as you will: This user’s alignment is Lawful Good: the “Crusader.” Specifically referring to him as a “green movement activist” is however somewhat of a stretch without evidence of direct activism to advance uniquely “green movement” objectives, “Green Party activist” per Heartland is a somewhat better description.
By my analysis he’s just a know-it-all wannabe-politician who claims the natural right of leadership due to self-determined intellectual superiority. Lord knows we enough of that sort running around.
Gillian (March 12, 2012 at 12:29 am) points to Frank O’Dwyer’s continuing critique of Brandon Shollenberger’s reviews.
He doesn’t seem to have comments enabled. Here’s a repost of a comment left last week at Climate, Etc. It refers to Shollenberger’s preliminary tacking of Tiljander, and is even more apt given his added attention to this subject in the “Technical Review.”
Too much brokenness to answer it all, but:
>> Annual temperatures can be (partially) reconstructed from more restricted temperatures, for example from growing season temperatures. This can be empirically verified, by examining the instrumental record
> Which instrumental record? The raw data from the instruments? Or the “adjusted”data? If adjusted, which version?
You’ve failed to understand. I’ll try again. We have an idea: maybe it is possible to retrieve useful information about past temperatures even if you don’t know the entire annual temperature record. Perhaps there is a correlation between parts of the year and the annual value. Its a reasonable idea, but it should be tested. How might we test it? Well, we could just construct synthetic series with roughly the expected statistical properties and try that. Or we could use climate model output. Or we could look at the instrumental record. You could use any version of it you like. Of course you don’t actually need to do any of this yourself – because it has already been done. Its in those papers that you’re pretending to have read.
> Before the MWP disapeared [sic]?
Sorry guv, you’ve got the wrong strawman. The MWP preceeedes the instrumental record by a fair while.
> After you get done answering that, could you advise as to how the tree ring data, which represents growing season only, is adjusted to account for variations in precipitation?
Again, its in the papers you’re pretending to have read. If WUWT was indeed the useful scientific resource you think it is, there would be a post here explaining this point, since it seems to confuse some.
> Sexton makes the highly-logical point that the tree-ring recorded damps out the highs and lows (like MWP and LIA)
But Sexton, like so many others, treats the MWP and LIA as givens. By some magical means not available to ordinary mortals, he “knows” the hemispheric average temperatures of these periods, and so he “knows” that the reconstructions must be wrong.
Normal scientists don’t have this magical knowledge, so they have to use the observations available instead.
> http://wattsupwiththat.com/2009/12/19/wikibullies-at-work-the-national-post-exposes-broad-trust-issues-over-wikipedia-climate-information/
That post is laughably inaccurate, as anyone who has a clue about wikipedia and how it works will realise. I attempt to explain the grosser errors at http://scienceblogs.com/stoat/2010/01/a_childs_garden_of_wikipedia_p.php
Ignoring all the well-known problems with MBH98 etc, there is another reason why the whole thing may be fraudulent.
Here’s a basic question: why did Mann use PCA to derive his reconstruction? In his excellent book ‘The Hockey Stick Illusion’, Montford quoted a world authority on statistics, saying that the use of PCA may not have been appropriate.
.
When most people, including politicians, look at the hockey stick graph they will assume it represents the average temperature derived from the proxies. But it doesn’t. Whatever PCA generates, it isn’t an average. If it did generate an average there would be no point in using PCA, anyway.
As Steve McIntyre noted, if you take a simple average of all the proxy data there’s no sign of a hockey stick, and there is a pronounced MWP signal. Of course, this wouldn’t be scary enough.
.
If Mann had used a simple averaging process (as used by Loehle) there would be few opportunities to get the answer he wanted. But with PCA there are almost limitless opportunities to torture the data into submission.
.
When people see the hockey stick they assume it is an attempt to derive the average temperatures over the last thousand years or so. But it isn’t. It’s something else, a complex construct whose significance is only understood by statisticians. This is another reason why the hockey stick is, in a sense, a fraud.
Chris
William M. Connolley says:
March 11, 2012 at 2:01 pm
> where is the science which says one can gain information from no information?
You can’t. But that isn’t what I said, and it isn’t what the proxy reconstructions do. Annual temperatures can be (partially) reconstructed from more restricted temperatures, for example from growing season temperatures. This can be empirically verified, by examining the instrumental record – as I pointed out before, and as you failed to read. If you want to know the details, you’ll need to read the papers. Or RealClimate. But you certainly won’t find any of that information over here.
================================================================
I’ll take one last run at this, because you don’t seem to understand my question. My question wasn’t if we can gain temps from the rings. That’s a separate issue which is also worthy of a great deal of scrutiny.
You mention the growing season….. yes, the growing season for these particular trees in the particular locations are typically only 6 to 8 weeks out of the year. So, let’s pretend we can actually gain temps from the tree rings with decent accuracy. Where has it been demonstrated that if we know the temps for a 2 month period of time that we then know even in a general sense what the annual or decadal temperature mean will be? Forget the rings for a moment and say that we have actual thermometers measuring the temps in these locations for the time period of the growing season. You are stating if these temps are known, we can then know the mean temperature for the northern hemisphere on an annual or decadal basis. This is easy enough to prove. Please get back with us this summer and let us know how the rest of the year will turn out after the growing season in northern Canada or Yamal is done. Never mind, I’ve been looking for a debunking project anyway.
From William M. Connolley on March 12, 2012 at 4:43 am:
But we already know how Wikipedia is supposed to work, and how you work Wikipedia. Why must we give your blog a hit at an old post to read self-justifications you can’t be bothered to present here?
Richard S Courtney:
I found that one rather confusing. I pointed out Mann misrepresented a source. Frank o’Dwyer responded by saying Mann didn’t misrepresent that source because other sources said what Mann claimed while offering another source which doesn’t say it either (saying there are other possibilities doesn’t mean you’re claiming those other possibilities are true).
But to be fair, he did raise a meaningful issue in regard to the Wegman situation. I discuss it here. Long story short, one can argue Wegman didn’t admit there was any “substantial collaboration,” and thus, what I said was “wrong.” However, as I explain in that link, if you don’t consider what Wegman admitted to to be substantial collaboration, then you have to accept the fact Wegman didn’t say one way or the other about substantial collaboration.
So you can say I was wrong with my criticism of Mann, but if you “correct” it, the exact same point remains. No matter how you look at it, Mann falsely claims Wegman denied something under oath that was (apparently) true.
Delighted to see WMC once again put on the dancing shoes…
Instrument record is the equivalent of random statistical noise is the equivalent of computer models as far as checking for proxies mirroring the period temperature. Wow! Just wow!
It literally boggles the mind!
Oh, not really equivalent, just throwing out ideas… GIGO