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December 21, 2009, 12:01:00 | NP Editor
There's trouble over tree rings as the Climategate emails reveal a rift between scientists.
By Terence Corcoran

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.
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 on
Saturday 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 Center, 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.

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 Ra**** Hanntemirov from Russia in October 1998 - implying that warming has
been common in the past and nothing unusual was happening today.
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.
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 ****ed 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."

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.

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-skeptic 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 skeptics, manipulate the
peer-review process and isolate all skeptics 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..."

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."

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 Nov. 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.
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 Nov. 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 a 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
imbedded 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.
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