First published at the National Post: December 21, 2009, 2:33 pm
There’s trouble over tree rings as the Climategate emails reveal a rift between scientists. For Part 1, go here.
In the thousands of emails released last month in what is now known as Climategate, the greatest battles took place over scientists’ attempts to reconstruct a credible temperature record for the last couple of thousand years. Have they failed? What the Climategate emails provide is at least one incontrovertible answer: They certainly have not succeeded.
In a post-Copenhagen world, climate history is not merely a matter of getting the record straight, or a trivial part of the global warming science. In a Climategate email in April of this year, Steve Colman, professor of Geological Science at the University of Minnesota Duluth, told scores of climate scientists “most people seem to accept that past history is the only way to assess what the climate can actually do (e.g., how fast it can change). However, I think that the fact that reconstructed history provides the only calibration or test of models (beyond verification of modern simulations) is under-appreciated.”
If temperature history is the “only” way to test climate models, the tests we have on hand — mainly the shaky temperature history of the last 1,000 or 2,000 years — suggest current climate models are not getting a proper scientific workout.
Two scientists, one British and the other American, straddle the initial Climategate battle over recent global temperature history. Later, the same two scientists appear to abandon their internal disagreements and join forces to present a united front to fight off critics and put down skeptics.
Mann came to dominate the paleoclimate effort
In the United Kingdom, Keith Briffa, at the University of East Anglia’s Climatic Research Unit — from where the emails appear to have been hacked or leaked — headed one of the main scientific projects. His specialty is dendroclimatology, the study of tree rings to reconstruct past climate records. In 1998, Mr. Briffa played a lead role as East Anglia’s CRU tried to fulfill its mandate from the IPCC, the UN Intergovernmental Panel on Climate Change: develop official global temperature data records.
In June 1998, a new player dramatically crashed the official CRU paleo world. As described in the first part of this two-part series on Climategate, U.S. scientist Michael Mann was invited to become part of the official effort to create a history of global temperatures. Then adjunct assistant professor of geosciences at the Morrill Science Centre, University of Massachusetts, Mr. Mann would soon come to dominate the IPCC paleoclimate effort.
Like all paleoclimatologists, Mr. Briffa and Mr. Mann both used various proxies. Actual temperature records exist only from the late 1800s, forcing scientists to use uncertain indirect methods — ice core samples, tree-ring measurements, rock formations — to determine what temperatures might have been 500, 1,000 and 5,000 years ago. Mr. Briffa focused much of his attention on Russia, where scientists scoured Siberia for tree ring data.
The Mann-Briffa confrontation
When Mr. Mann joined the UN global paleo project, he had already finished “Global-scale temperature patterns and climate forcings over the past six centuries,” a paper written with Ray Bradley, at the University of Massachusetts, and Malcolm Hughes, a meso-climatologist and Professor of Dendrochronology in the Laboratory for Tree-Ring Research at the University of Arizona. The core of that paper was a graphic that would come to be known as the “hockey stick” presentation of northern hemisphere temperatures over the past centuries. It was called the hockey stick because it appeared to show a flat temperature run and a sharp uptick in the last 50 years.
The main Mann-Briffa confrontation took place in the spring of 1999 after Mr. Briffa submitted a paper to Science magazine, critiquing elements of the hockey stick and presenting his own 2,000-year tree-ring-based paleo record.
Mr. Briffa sent Mr. Mann a copy of his Science article on April 12, advising Mr. Mann that he had “decided to mention uncertainties in tree-ring data while pushing the need for more work”. Earlier emails also show Mr. Briffa struggling with Russian tree-ring results and the reports of Russian scientists on their difficulties. Their findings often contradicted the idea that the world is warmer today than hundreds or even thousands of years ago. “Relatively high number of trees has been noted during 750-1450 AD. There is no evidence of moving polar timberline in the north during the last century,” wrote Rashit Hanntemirov from Russia in October 1998 — implying that warming has been common in the past and nothing unusual was happening today.
Mann blew up at Briffa’s paper — “very misleading”
The reference to 750-1450 would appear to support the long-held scientific view on the existence of a Medieval Warm Period that might have been hotter than the 20th century. A couple of weeks later, another Russian, Eugene Vaganov, wrote in a paper saying that “the warming in the middle of the 20th century is not extraordinary. The warming at the border of the 1st and 2nd millennia was more long in time and similar in amplitude.”
Mr. Briffa, in his Science paper, proposed his own 2,000-year record as an alternative to Mr. Mann’s hockey stick, using other data, including collections from Sweden and Yamal, in Siberia. The paper raises issues that cast doubt on Mr. Mann’s version of climate history. Mr. Mann notoriously posits that the widely accepted existence of a Medieval Warm Period, and a subsequent Little Ice Age, are scientifically dubious phases that never happened. When Mr. Mann saw the pre-publication version of Mr. Briffa’s critical paper, he blew up. In an April 13 email, he wrote to Mr. Briffa complaining that his work is “very misleading” and that it is “a bit unfair” in the way Mr. Briffa presents Mr. Mann’s perspective.
Mr. Mann said another section in Mr. Briffa’s paper was “incorrect” and that it misrepresented the level of uncertainty in Mr. Mann’s work. “Our uncertainties are based both on 20th century calibration and independent confirmation from 19th century data. PLEASE MAKE SURE this is clear.” Mr. Mann asks Mr. Briffa to remove parts of his 2,000 year graph. Mr. Mann criticized Mr. Briffa for using tree-ring density data as opposed to the tree-ring width data that Mr. Mann had been using because he found density measures inadequate.
Bradley “disassociates” himself from Mann, advises Briffa
Finally, in an important concluding remark, Mr. Mann tells Mr. Briffa to “correct” his definitions regarding “global temperature and non-temperature proxies.” Mr. Mann prefers using the words “global climate proxies,” thus giving the impression that proxies from tree rings and other sources and actual temperatures are one and the same for IPCC purposes. What Mr. Mann appears to be talking about here is the use of what CRU head Phil Jones would later refer to as Mr. Mann’s “trick” and how he was able to “hide the decline” that Mr. Briffa’s tree-ring research showed 20th century temperatures to be cooler rather than warmer.
A series of email exchanges, some heated and involving a range of scientists, follows. It appears, moreover, that Mr. Mann had interfered with the peer-review process of Mr. Briffa’s article at Science magazine. One of Mr. Mann’s associates, Raymond Bradley at the University of Massachusetts, on April 19, wrote to Science editor Julia Uppenbrink, saying, “I would like to disassociate myself from Mike Mann’s view” regarding the climate warming article. Mr. Bradley sends a blind copy of this email to Mr. Briffa.
The conflict eventually makes it up to Phil Jones, the head of CRU, who writes a stinging letter to Mr. Mann on May 6. “You seem quite pissed off with us all in CRU,” said Mr. Jones. “I am somewhat at a loss to understand why.” Mr. Jones, in strong words, then rips into Mr. Mann. He accused Mr. Mann of “slanging us all off to Science.” We all have disagreements, wrote Mr. Jones, but “We have never resorted to slanging one another off to a journal… or in reviewing papers or proposals.”
After a month of back and forth, Mr. Mann seems to offer an apology. In a mildly grovelling but self-serving and ultimately not-too-apologetic letter, he commends Mr. Briffa and others for doing such terrific work. “I appreciate having had the opportunity to respond to the original draft… We have some honest disagreements among us… Thanks for all the hard work and a job well done,” wrote Mr. Mann on May 14. Mr. Bradley, Mr. Mann’s associate in Massachusetts and co-creator of the hockey stick graph, sends a private response to Mr. Briffa: “Excuse me while I puke… Ray.”
Recent warmth “probably matched” 1000 years ago
More clashes occur later that year over the tree-ring record. Mr. Briffa, in September 1999, is still battling Mr. Mann. “I know Mike thinks his series is ‘the best’, and he might be right — but he may also be too dismissive of other data and overconfident of his own.” He adds: “I know there is pressure to present a nice tidy story as regards ‘apparent unprecedented warming in a thousand years or more in the proxy data,’ but in reality the situation is not quite so clear… I believe the recent warmth was probably matched about 1,000 years ago.”
At this point in the Climategate emails, the stage has been set for a decade of high drama. Over the next 10 years, the emails become a zone of internal conflict and external battles to suppress criticism, ridicule critics and resist all outside interference with the official science story they had assembled: The late 20th century was the warmest in history, and the next 100 years could be a climate nightmare.
Waged war on papers questioning official view
The Mann technique of aggressive intervention in the peer-review process over Mr. Briffa’s work sets the tone for what would become a major strategy as all the scientists within the IPCC loop waged war on any science and papers that contravened or questioned the official view.
The anti-sceptic campaign switched into overdrive with the arrival on the climate science scene of two Canadians, Steve McIntyre and Ross McKitrick. In mid-2003, after many efforts, Mr. McIntyre and Mr. McKitrick finally published a paper titled “Corrections to the Mann et al. Proxy Data Base and Northern Hemisphere Average Temperature Series.”
The public battles between Mr. Mann and the two Canadians are already on the record. The emails reinforce the worst of suspicions that the official scientific community did all they could to smear Mr. McIntyre and Mr. McKitrick, prevent publication of the work of sceptics, manipulate the peer-review process and isolate all sceptics as cranks. On May 31, 2004, Phil Jones, head of the IPCC-designated Climatic Research Unit, wrote to Mr. Mann: “Recently rejected two papers (one for JGR and for GRL) from people saying CRU has it wrong over Siberia. Went to town in both reviews, hopefully successfully. If either appears I will be very surprised…”
Embattled scientists fight to interfere with FOI process
Mr. Mann meddled in other ways. In January 2005, he called the editor of Geophysical Research Letters, the official science publication of the American Geophysical Union, to try to head off a paper by Mr. McIntyre. The editor, Steve Mackwell, defends the decision to publish and tells Mr. Mann that the McIntyre paper has been thoroughly peer reviewed by four scientists. “You would not in general be asked to look it over,” Mr. Mackwell told Mr. Mann. Later in 2005, Mr. Mann wrote to Mr. Jones on their troubles with the GRL journal after Mr. Mackwell’s term as editor was up: “The GRL leak may have been plugged up now w/ new editorial leadership.”
Mr. McIntyre, a mining exploration expert based in Toronto, and Mr. McKitrick, an economics professor at the University of Guelph, continued to dog Mr. Mann’s view of climate history. First they wanted release of the data behind the hockey stick graph and the computer code that produced various trend lines. When Mr. Mann and CRU declined or resisted, Mr. McIntyre began filing Freedom of Information requests in the United States and Britain. The emails portray embattled scientists fighting desperately to interfere with official FOI processes. One now widely-circulated email, by Mr. Jones, asked Mr. Mann: “Can you delete any emails you may have had with Keith re AR4? Keith [Briffa] will do likewise. He’s not in at the moment — minor family crisis. Can you also email Gene and get him to do the same? I don’t have his new email address. We will be getting Caspar to do likewise.”
McIntyre exposes Yamal cherry-picking
In this email, Mr. Jones is asking key scientists who worked on AR4 — the 4th Assessment Report on the science of climate change produced by the IPCC in 2007 — to erase all emails related to that report. Caspar Ammann is a scientist at the Climate and Global Dynamics Division of U.S. National Centre for Atmospheric research. His area is natural climate variability and change over the past centuries and millennia and their application to climate change.
The emails take another turn against the IPCC scientists after Mr. McIntyre got his hands on some of the tree-ring data collected by Russian scientists in Yamal in Siberia. It appeared to Mr. McIntyre that Mr. Briffa, in producing another hockey-stick like result in 2007, cherry-picked tree rings. Mr. Briffa, once at war with Mr. Mann over climate records, now found himself aligned with Mr. Mann in defending the hockey stick. After Mr. McIntyre revealed his Yamal tree ring findings on his ClimateAudit blog, and Ross McKitrick wrote of the Briffa Yamal tree-ring issue in the Financial Post this past October, the emails again lit up with fresh rounds of defensive fire.
Within weeks, however, the private email battle would overtake the skirmish over the latest public McIntyre findings. On November 17, with release of the Climategate emails, the 13-year battle over climate history and climate forecasting would be all over the Internet and the media.
The epic stories in the emails, in any honest reading, do not produce any concrete results or conclusions regarding the state of the science.
Emails inconclusive, but global warming perhaps not unprecedented
What exists now in the public domain is scientific conflict and uncertainty that goes to the heart of climate change science — past, present and future.
As recently as November 28, a posting on the Mann-related website, RealClimate.org, continues to claim the Medieval Warm Period and the Little Ice Age never happened. If that is scientifically provable, then it might be true that the last 50 years have been the hottest in a thousand years, offering some support to the idea that man-made climate change is changing the climate in a significant and unprecedented way. But if the Medieval Warm Period (MWP) and the Little Ice Age did occur, then the Earth may have been just as warm today as it was 1,000 years ago. If that’s the case, the hockey stick graph and the official paleoclimate record is at best uncertain or, at worst, a scientific trick.
It is, in my view, not possible for a layman, or even an expert, to make any assessment of the tree ring data conflicts — to pick one issue — based on the emails. Masses of computer code and data are embedded in the Climategate documents, enough to keep a full science inquiry busy for months, if not years. Exactly who did what with which data requires a full investigation by competent scientists and official bodies.