HOCKEY NIGHT IN CANADA:

Let science debate begin (Terence Corcoran, January 27, 2005, National Post)

For some time now this page has been publishing comment on The Hockey Stick, the central piece of scientific evidence for the United Nation's claim that the world is warmer now than at any time in the last 1,000 years. Today we begin a major two-part investigation that delves deeper into the foundations for what may well be the most important economic, scientific and business graphic in world history.

Created by Michael Mann, currently assistant professor, department of environmental science, University of Virginia, the hockey stick purports to plot temperatures in the Northern Hemisphere back 1,000 years. For the most part, the line appears relatively stable leading up to the 20th century, when it turns sharply upward, forming the blade of the hockey stick.

The hockey-stick image has appeared in countless documents and hundreds of speeches. The opening graphic in the recently-published Arctic Climate Impact Assessment report reproduces the Mann chart as the main springboard to hundreds of pages on climate risks in the Arctic. It is also the core justification for the Kyoto Protocol, which comes into effect on Feb. 16.

Until now, criticisms of the hockey stick have been dismissed as fringe reports from marginal global warming skeptics. Today, however, the critical work of two Canadian researchers, Ross McKitrick, an economics professor at Guelph University, and Toronto consultant Stephen McIntyre, will be published by Geophysical Research Letters, the prestigious journal that published one of the early versions of Michael Mann's 1,000-year tracking of Northern Hemisphere temperatures,

Publication in Geophysical Research sets McIntyre and McKitrick's analysis and conclusions in direct opposition to the Mann research. Their criticism can no longer be dismissed as if it were untested research posted on obscure Web sites by crank outsiders. Their work is now a full challenge to the dominant theme of the entire climate and global warming movement.

The story of McIntyre and McKitrick's research, and their attempt to recreate the hockey stick, is the subject of the special two-part commentary that begins today. Written by Marcel Crok, an editor with the Dutch science magazine Natuurwetenschap & Techniek, the article chronicles the mystery behind the unraveling of the hockey stick.

The lone Gaspe cedar (Marcel Crok, January 28, 2005, National Post)

When we put forward some of the criticism to Mann, Bradley and Hughes in an e-mail, we received an elaborate response within the hour. Apart from the stock arguments that McIntyre and McKitrick are not real scientists, Mann rationalized the presence of the directory BACKTO_1400-CENSORED on his FTP site: "After publication of the first hockeystick in 1998, we ran a number of sensitivity tests to determine if we could come to a reliable reconstruction without having to correct certain tree ring series at high altitudes for non-climatological effects, like the influence of CO2. We reported on this in the publication of 1999."

McIntyre is not satisfied: "In his second publication, Mann mentioned problems with the bristlecone pines, but only with regards to the period of 1000-1399 and not the 15th century that is in this file. More importantly, if you know there are problems with the bristlecone pines, the obvious test would be to eliminate them from the calculation and see what the effect is. This is exactly what Mann did in the directory BACKTO_1400-CENSORED. When he did not like the results, he did not report them and proceeded to include the bristlecone pines in his final analysis."

We asked Mann about the apparent inconsistency between the claimed robustness and the evidence that the shape of his hockey stick relies heavily on the bristlecone pines. Mann responds that he can reach the same results even without doing a PCA, arguing that you could simply use all 95 proxies individually in the calculations: "There is no clearer proof that McIntyre and McKitrick claims are false."

"Mann is a clever debater," McIntyre points out. "That he can produce a hockey stick with another method that also allows the bristlecone pines to dominate is completely irrelevant. The bristlecone pine series are still essential for this new result. When you do the calculation without the bristlecone pines, the result does not resemble a hockey stick in any way."

Mann further argued that he is not the only scientist to have found the hockey stick graph: "Over a dozen other estimates based on proxy data yield basically the same result." That argument is not new to McIntyre.

At this point, McIntyre has growing doubts about the other studies as well. His initial impression is that they are also dubious. It is almost certain, or so he states, that the other studies have not been checked either. McIntyre: "Mann's archiving may be unsatisfactory, but other researchers, including Crowley, Lowery, Briffa, Esper, etc, are even worse. After 25 e-mails requesting data, Crowley advised me that he had misplaced his original data and only had a filtered version of his data. Briffa reported the use of 387 tree ring sites, but has not disclosed the sites. Other researchers haven't archived their data or methods or replied to requests."

"Mann speaks of independent studies, but they are not independent in any usual sense. Most of the studies involve Mann, Jones, Briffa and/or Bradley. Some data sets are used in nearly every study. Bristlecone pine series look like they affect a number of other studies as well and I plan to determine their exact impact. I'm also concerned about how the proxies are selected. There is a distinct possibility that researchers have either purposefully or subconsciously selected series with the hockey stick shape. I'm planning to use simulations to test if the common practice of selecting the so-called "most temperature sensitive" series also yield hockey sticks from red noise."

McIntyre and McKitrick draw far reaching conclusions from their research: "When the IPCC decides to base their policy on such studies, triggering the spending of billions of dollars, there should be more thorough checks. At some point, some one should have done an elementary check on the principal component calculations. This never happened and there is no excuse for this."

Rob van Dorland of the Royal Netherlands Meteorlogical Institute has read the article that will appear in Geophysical Research Letters and is convinced it will seriously damage the image of the IPCC. "For now, I will consider it an isolated incident, but it is strange that the climate reconstruction of Mann has passed both peer review rounds of the IPCC without anyone ever really having checked it. I think this issue will be on the agenda of the next IPCC meeting in Peking this May."

This brings climate research back to square one. McIntyre: "Our research does not say that the earth's atmosphere is not getting warmer. But the evidence from this famous study does not allow us to draw any conclusions about its extent, relative to the past 1000 years, which remains as much a mystery now as it was before Mann's article in 1998."

Funny how often all the scientific sturm and drang ends up back at square one.

Posted by Orrin Judd at February 4, 2005 7:38 AM