Chapter excerpt on Michael Mann & Hockey Stick: From best-selling The Politically Incorrect Guide to Climate Change by Marc Morano
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CHAPTER 6
The Hottest Temperatures in a Thousand Years! Michael Mann’s Hockey Schtick
Penn State professor Michael Mann rose to climate fame with his 1998 study including the now infamous “hockey stick” graph, which purported to show that the Northern Hemisphere today is experienc- ing high temperatures unprecedented in almost a thousand years. The graph was called “the hockey stick” because it resembled a hockey stick lying on its side, with the blade being the supposed spike in temperatures in the twentieth century. Mann’s ominous temperature graph was featured in the UN IPCC’s Third Climate Assessment report in 2001, and he became a media celebrity.
Mann’s hockey stick became the perfect poster illustrating the narrative of man-made global warming. As the BBC explained, “It is hard to overes- timate how influential this study has been.”1
Influential? Yes. Accurate? No.
Peer-reviewed research both before and after Mann’s hockey stick show that both the Medieval Warm Period and the Roman Warm Period were as warm as or warmer than modern temperatures. In fact, the 1990 UN IPCC report originally featured a temperature chart showing a Medieval Warm Period that was much warmer than twentieth-century temperatures.
While there were claims that the IPCC chart only represented tempera- tures in England, NASA climate researcher James Hansen also showed a very similar chart of medieval temperatures in his 1984 study, “Climate Sensitivity to Increasing Greenhouse Gases.” Hansen and his co-authors write that the chart, which was from 1981, represents the “global tempera- ture trend” for the past “millennium,” and “is based on temperatures in central England, the tree limit in the White Mountains of California, and oxygen isotope measurements in the Greenland ice.”3
Tony Heller of RealClimateScience.com wrote that Hansen’s 1981 chart for his study shows “that claims the 1990 IPCC MWP graph was derived from CET (Central England Temperatures) only—are bogus. It came from Hansen 1981, and used multiple global proxies.”4
Climate analysts “frequently claim that the 1990 IPCC temperature graph…showing the Medieval Warm Period (MWP) was only a representation of Central England Temperatures (CET) and was not global,” Heller said. But Hansen’s graph “was taken from temperatures in England, California and Greenland,” he explained.
On December 1, 1992, the New York Times reported that both the Medieval Warm Period and Little Ice Age were “global climate phenomena, not regional temperature variations.” The paper quoted researchers who had compiled “a detailed record of the year-to-year variation in temperature and precipitation over the last thousand years” and found the “unmistakable signatures of the Medieval Warm Period, an era from 1100 to 1375 A.D. when, according to European writers of the time and other sources, the climate was so balmy that wine grapes flourished in Britain and the Vikings farmed the now-frozen expanse of Greenland; and the Little Ice Age, a stretch of abnormally frigid weather lasting roughly from 1450 to 1850.”
The Times article quoted researcher Lisa J. Graumlich asking “how did we get those warmer temperatures during pre-industrial times, and what can we learn from those conditions about what is going on today?”5
Great question. But the climate campaigners are not interested in answering it. Instead they have waged a decades long battle to rewrite climate history and eliminate the inconvenient Medieval Warm Period.
Hiding the Medieval Warm Period
In 2006, I was the communications director for the U.S. Senate Environment and Public Works Committee. We held a hearing featuring geologist David Deming, who testified to our committee about attempts to get rid of the Medieval Warm Period. Deming had written about his surprising encoun- ter, “With the publication of the article in Science, I gained significant credibility in the community of scientists working on climate change. They thought I was one of them, someone who would pervert science in the service of social and political causes. So one of them let his guard down. A major person working in the area of climate change and global warming sent me an astonishing email that said ‘We have to get rid of the Medieval Warm Period.’”6
Who was the “major person” who wanted to “get rid of” the Medieval Warm Period, according to Deming? Deming “to the best of my recollection” fingered Jonathan Overpeck as the email culprit.7 Overpeck, a researcher at the University of Arizona before moving to the University of Michigan, was a lead author on the 2007 and 2013 UN Intergovernmental Panel on Climate Change reports.
The emails leaked in the Climategate scandal, which we’ll discuss in greater detail in chapter ten, revealed that Overpeck was concerned that Deming might be “taking the quote out of context.” 8
But Overpeck is on record denying the reality of the Medieval Warm Period. In 1999, he declared, “Now, high-resolution paleoclimate records stretching back 1,200 years confirm that the so-called Medieval Warm Period did not exist in the form of a globally synchronous period as warm, or warmer, than today.” He was frustrated by the Medieval Warm Period’s impact on the climate change debate, as a 2005 email from him, exposed in Climategate, revealed: “I’m not the only one who would like to deal a mortal blow to the misuse of supposed warm period terms and myths in the literature.”9
But despite Overpeck’s claims and what was implied by Mann’s infamous hockey stick, the Medieval Warm Period—also called the Medieval Climate Optimum—is not a myth. The most recent research clearly shows that it was real—and was in fact global, not just confined to the Northern Hemisphere. The Center for the Study of Carbon Dioxide and Global Change reported in 2017 that “the Medieval Warm Period was: (1) global in extent, (2) at least as warm as, but likely even warmer than, the Current Warm Period, and (3) of a duration significantly longer than that of the Current Warm Period to date.”10
And as the Science and Public Policy Institute reported in 2009, “More than 700 scientists from 400 institutions in 40 countries have contributed peer-reviewed papers providing evidence that the Medieval Warm Period (MWP) was real, global, and warmer than the present. And the numbers grow larger daily.”11
A 2003 study by researchers from the Harvard-Smithsonian Center for Astrophysics, using more than two hundred paleoclimate studies from all over the planet, confirmed the existence of the MWP and LIA and found that twentieth-century warming was not unprecedented.12
A 2012 peer-reviewed study established medieval warming on the tropi- cal island of New Caledonia in the Southern Hemisphere.13 And a 2012 study published in the Geophysical Research Letters found that the subsequent
Little Ice Age (LIA) was probably caused by low solar and volcanic activity. The study’s findings were “consistent with the idea that the LIA was a global event.”14 The LIA roughly occurred between 1300 to 1850.
Another 2012 study also added to the evidence that the MWP and LIA were both global in extent. Published by Elsevier, it examined the Antarc- tic Peninsula and “builds the case that the oscillations of the MWP and LIA are global in their extent and their impact reaches as far South as the Ant- arctic Peninsula…. ”15
The Hockey Stick Breaks under Scrutiny
Geologist Robert Giegengack of the University of Pennsylvania detailed his initial reaction to the Mann’s hockey stick graph: “I didn’t like it when I first saw it. And when I saw that occur, two things occurred to me. One—I missed the medieval warm phase, which was very, very well documented. And most people who look at the medieval warm phase think that the temperature was higher than it is now. And the second thing I saw was a kink in his curve, and the kink exactly coincided with the change in the way the measurements were made.” Giegengack’s criticism of Mann’s meth- odology was scathing. “He’s not combining apples and oranges, he is com- bining apples and elephants and joining them on the same plot,” Giegengack explained. “Where is the medieval warm phase? It has been detected in glaciers now in New Zealand. The medieval warm phase was real.”16
Professor Ross Mckitrick of the University of Guelph in Canada and statistician Steve McIntyre were the duo instrumental in taking down the hockey stick.
“I had a problem when I looked at the [UN IPCC] report, first of all how promotional it was. This same graph reappears over and over throughout the report. It appears in different forms. Anywhere it appears it’s full color. It’s obvious that the people who put the report together wanted to promote it heavily,” McKitrick, a senior fellow of the Fraser Institute and an adjunct scholar of the Cato Institute, explained.17
“I also had a problem with the fact that the author of that study (Mann) was the lead author of the [IPCC] chapter that promoted it and I didn’t like the idea that a panel that was supposed to assess the whole literature oper- ates in that way—where somebody assesses basically their own work and decides that it’s the best thing out there and promote it heavily. It turns out the IPCC does that on lots of topics. They pick an author whose work they like, put them in charge of the chapter and then, what do you know? The chapter turns out to promote heavily that person’s work and dismisses everything that says something else.”
McKitrick teamed with Steve McIntyre to dig deeper into the hockey stick. The first problem they encountered was in getting access to the data that Mann had used to create it.
“It struck Steve as extremely odd that here is this famous study—govern- ments around the world are relying on it, scientists were citing it inten- sively—and obviously nobody had ever asked to see the guy’s data because they didn’t have it in any one place,” McKitrick said. “I got contacted by McIntyre who worked in the mineral finance field and he had actually unpacked some of the math, and got the data set from the authors and was finding all kinds of problems in the calculations.”
McKitrick pointed out, “If you do your calculations correctly they’ll show you that the uncertainties are so large you can’t really say anything about what the results are. And in this case the method they used understated their uncertainties. So that they claim to have a lot more precision in their results [than] they really did. Also at a certain key point in the calculations, they—they just used the wrong formula,” he added.19
★★★★★
Protecting Their “Pet Findings” from Contradictory Evidence
Former UN IPCC climatologist John Christy ripped the UN’s role in “misrepresenting the tempera- ture record of the past 1000 years.” As Christy testified to Congress in 2011, “Regarding the Hockey Stick of IPCC 2001 evidence now indi- cates, in my view, that an IPCC Lead Author work- ing with a small cohort of scientists, misrepresented the temperature record of the past 1000 years by (a) promoting his own result as the best estimate, (b) neglecting studies that con- tradicted his, and (c) amputating another’s result so as to eliminate conflicting data and limit any serious attempt to expose the real uncertainties of these data.” “UN IPCC Lead Authors have virtu- ally total control over the material and behave in ways that can prevent full disclosure of the infor- mation that contradicts their own pet findings and which has serious implications for policy in the sections they author.” As Christy complained, “Lead Authors were transformed from serving as Brokers of science to Gatekeepers of a preferred point of view.”18
Atmospheric physicist Fred Singer applauded the investigations of McIntyre and Mckitrick, noting that their research “showed that even random data fed into the faulty Mann theory would always yield a record- warmest 20th century.”20 Singer added, “Medieval temperatures were substantially greater—and so were temperatures during the earlier Roman Warm Period.”
German professor Richard Dronskowski of Aachen University said, “No chart has been so falsified as the hockey stick chart. It’s an embarrassment for the IPCC.” Dornskowski called Mann’s graph “a very, very nasty fabrication.”21
A 2016 analysis at the website “No Tricks Zone” presented fifty “non-Hockey Stick Graphs” that had been published in peer-reviewed scientific papers and that refute the impression that modern temperatures are unusually warm. “All the graphs show that modern (post-1940s) tem- peratures aren’t any warmer than the decades and centuries and millen- nia prior to the steep increase in anthropogenic CO2 emissions,” the analysis concluded.22
Replicating Error
Despite the damning criticisms of Mann’s work, many studies that followed, complete with hockey stick–style graphs of their own, appeared to support his conclusions.
But the 2006 Wegman Report commissioned by Congress exposed that Mann and the scientists whose work appeared to replicate his were operating in an echo chamber. “We found that at least 43 authors have direct ties to Dr. Mann by virtue of coauthored papers with him. Our findings from this analysis suggest that authors in the area of paleoclimate studies are closely connected and thus ‘independent studies’ may not be as independent as they might appear on the surface,” the report explained.23
And in 2011, Steve McIntyre reported at Climate Audit that the leaked “Climategate documents confirm Wegman’s hypothesis.” As McIntyre wrote, “The Wegman Report was vindicated on its hypothesis about peer-review within the Mann ‘clique.’”
“The Wegman Report hypothesized, but were [sic] unable to prove, that reviewers in the Mann ‘clique’ had been ‘reviewing other members of the same clique’. Climategate provided the missing evidence, Climategate documents showed that clique member Phil Jones had reviewed papers by other members of the clique, including some of the articles most in contro- versy—confirming what the Wegman Report had only hypothesized,” McIntyre wrote.
So the studies “weren’t really independent,” added Ross McKitrick. Instead, “A whole bunch of other researchers in the field started using their principal components series in their own reconstruction. So they’re all sticking this biased hockey stick shape series in their data sets and getting a hockey stick result and then Mann turns around and says, ‘Oh! Well, look at all these other studies. They get a hockey stick too.’ Well, basically they’re using the same data and some of the same methods,” McKitrick explained.24
Bo Christiansen, a Danish Meteorological Institute scientist came to a similar conclusion. “We cannot from these reconstructions conclude that the previous 50-year period has been unique in the context of the last 500-1000 years,” Christiansen wrote. He dismissed claims that other reconstructions also show a “hockey stick,” noting that “the different reconstructions all shared the same problems…all proxies are infected with noise.”25
Mann has claimed that his study’s tempera- ture claims were vindicated by a 2006 National Academy of Sciences report, but as the Hockey Schtick website pointed out, The NAS report did nothing of the sort, and in fact validated all of the significant criticisms of McIntyre & McKitrick (M&M) and the Wegman Report….
The NAS found that Mann’s methods had no validation (CE) skill significantly different from zero….
Mann never mentions that a subsequent House Energy and Commerce Committee report chaired by Edward Wegman totally destroyed the credibility of the “hockey stick” and devastatingly ripped apart Mann’s methodology as “bad mathematics.” Fur- Furthermore, when Gerald North, the chairman of the NAS panel— which Mann claims “vindicated him”—was asked at the House Committee hearings whether or not they agreed with Wegman’s harsh criticisms, he said they did:
CHAIRMAN BARTON: Dr. North, do you dispute the conclusions or the methodology of Dr. Wegman’s report?
DR. NORTH [Head of the NAS panel]: No, we don’t. We don’t disagree with their criticism. In fact, pretty much the same thing is said in our report.
DR. BLOOMFIELD [Head of the Royal Statistical Society]: Our committee reviewed the methodology used by Dr. Mann and his co-workers 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.
WALLACE [of the American Statistical Association]: “The two reports [Wegman’s and NAS] were complementary, and to the extent that they overlapped, the conclusions were quite consistent.” [Emphasis in the original]27
A Book You’re Not Supposed to Read
The Hockey Stick Illusion by A. W. Montford (Anglosphere Books, 2015) exposes “in delicious detail, datum by datum, how a great scientific mistake of immense political weight was perpetrated, defended and camouflaged by a scientific establishment that should now be red with shame.”
—British science journalist Matt Ridley26
Dissension in the Ranks
Mann’s hockey stick and his research team have been subjected to intense scrutiny even by other warmist climate researchers and institutions.
A 2010 analysis by UK Royal Statistical Society head David Hand found that Mann’s hockey stick graph was “exaggerated.” According to Hand, “The particular technique they used exaggerated the size of the blade at the end of the hockey stick. Had they used an appropriate technique the size of the blade of the hockey stick would have been smaller.” As the professor explained, “The change in temperature is not as great over the 20th century compared to the past as suggested by the Mann paper.”28
One of Mann’s colleagues had emailed about “Mike’s Nature trick” to “hide the decline” in his temperature chart.
“I’ve just completed Mike’s Nature trick of adding in the real temps to each series for the last 20 years (ie from 1981 onwards) and from 1961 for Keith’s to hide the decline,” Phil Jones, then director of Climatic Research Unit at University of East Anglia wrote in a 1999 email.29
“Mike” was Michael Mann, who had produced his hockey stick by grafting historical data from tree rings as proxies for northern hemisphere temperatures onto modern thermometer observations to produce the hockey stick temperature chart.
After about 1961 the tree ring data showed a decline in temperatures, contrary to the actual thermometer data, which showed an increase in temperatures. Switching from the proxy tree-ring data to the actual temperatures were Mann’s “trick” to “hide the decline.”
“Any scientist ought to know that you just can’t mix and match proxy and actual data,” said Philip Stott, professor emeritus of biogeography at London’s School of Oriental and African Studies. “They’re apples and oranges. Yet that’s exactly what he did.”30
Worse, the discrepancy between the tree-ring dataset, which showed a decline, and the actual temperature measurements, which rose, raised questions about the validity of the purported proxy data from the tree rings. Mann’s graph and his use of his data came under harsh criticism from researchers.
The Climategate emails revealed that even Mann’s UN colleagues did not all buy his hockey stick. And the Climategate 2.0 emails—a second set of emails featuring the leading scientists of the UN IPCC released in 2012— exposed more skepticism about Mann’s work.
In a private 1999 email, Mann colleague Keith Briffa wrote, “I believe that the recent warmth was probably matched about 1000 years ago.” Briffa explained, “I do not believe that global mean annual temperatures have simply cooled progressively over thousands of years as Mike [Mann] appears to and I contend that that there is strong evidence for major changes in climate over the Holocene (not Milankovich) that require explanation and that could represent part of the current or future background variability of our climate.”31
UN IPCC scientist Tom Wigley had criticized the hockey stick in 2004. “I have just read the M&M [McIntyre and McKitrick] stuff criticizing MBH [Mann, Bradley, Hughes Hockey Stick]. A lot of it seems valid to me. At the very least MBH is a very sloppy piece of work—an opinion I have held for some time,” Wigley, the former director of the Climatic Research Unit at the University of East Anglia, wrote in 2004, in one of the Climategate emails.32 “Mike [Mann] is too deep into this to be helpful,” he added.
In subsequent years, Mann has tried to use the courts to silence his critics, filing defamation lawsuits against Canadian Climatologist Timothy Ball, the Competitive Enterprise Institute, National Review, and author Mark Steyn.33
Meanwhile the scientific studies refuting the hockey stick claims of unprecedented warmth in the twentieth century just keep piling up.
A 2012 peer-reviewed study in the journal Global and Planetary Change showed that the temperatures were warmer than twentieth-century tem- peratures one to two thousand years ago, “revealing warmth during Roman and Medieval times were larger in extent and longer in duration than 20th century conditions.”34 A paper published in Polar Research in 2011 found the that two locations in the Arctic were much warmer in the Medieval Warm Period than at the end of twentieth century.35 Yet another 2012 study, published in Palaeogeography, Palaeoclimatology, Palaeoecology, found, on the basis of isotopic records in Viking Age shells from Scotland, that the Medieval Warm Period “was warmer than the late 20th century by ~1°C.”36 A 2012, study published in Nature Climate Change added more evidence that medieval temperature were higher than today. “The international research team used these density measurements from sub-fossil pine trees in northern Scandinavia to create a sequence reaching back to 138 BC,” Phys.org reported.37 Their results showed a cooling trend since the Roman era. “For the first time, researchers have now been able to use the data derived from tree-rings to precisely calculate a much longer-term cooling trend that has been playing out over the past 2,000 years. Their findings demonstrate that this trend involves a cooling of -0.3°C per millennium due to gradual changes to the position of the sun and an increase in the distance between the Earth and the sun.” Jan Esper of Johannes Gutenberg University, the study’s lead author, explained, “We found that previous estimates of historical temperatures during the Roman era and the Middle Ages were too low.”38
A 2013 study in Science magazine examined “10,000 years of layered fossil plankton in the western Pacific Ocean,” and found that the Medieval Warm Period was 0.65 °C warmer than present temperatures. According to then–New York Times climate reporter Andrew Revkin, the paper reported “that several significant past climate ups and downs—including the medi- eval warm period and little ice age—were global in scope, challenging some previous conclusions that these were fairly limited Northern Hemisphere phenomena.”39 Revkin wrote of the study, “Michael Mann can’t be happy about this work.”40
