Hockey Stick Gets Checked

The Entrepreneurial View Raymond J. Keating July 19, 2006

It’s the paleoclimate community versus the statisticians.

That might not sound too exciting, but it demands the attention of anyone concerned about environmental policies and our economy as they relate to the debate over global warming.

The story started a few years ago. In a 2001 report, the United Nations’ Intergovernmental Panel on Climate Change (IPCC) concluded that the rise in temperatures in the Northern Hemisphere during the twentieth century was likely the largest in the past thousand years, and that the 1990s was the warmest decade and 1998 the hottest year over the past millennium. These conclusions were based on the work of Dr. Michael Mann and his colleagues in the late 1990s.

At the risk of mixing metaphors, the presumed smoking gun on man-made global warming was the “hockey stick” graph produced by Mann and Company. This showed a flat or even slightly declining temperature trend for nearly nine hundred years, followed by an unprecedented leap skyward, particularly in the very late twentieth century. Hence, the hockey stick shape.

Previously, temperature reconstructions generally showed a medieval warm period, which was warmer than the twentieth century.

The hockey stick graph was included in the IPCC’s report, and has since been peddled as undeniable evidence that man-made global warming is well underway, and will wreak havoc unless dramatic steps are taken by governments around the globe. Former Vice President Al Gore made just such a case based in part on the hockey stick graph in the film “An Inconvenient Truth.”

However, Mann’s statistical methodology came under sharp criticism by Ross McKitrick, an economist at the University of Guelph in Ontario, and Steven McIntyre, a veteran of mineral exploration and a former government policy analyst in Canada. McKitrick and McIntyre found several problems, including excluded data, truncated sources, obsolete data, and calculation mistakes. With corrections, according to McKitrick and McIntyre, that medieval warm period returns.

So, who is right? This question matters a great deal to those making public policy, and the rest of us affected by such policies. After all, the global warming activists proclaim that massive disease and destruction loom due to man-made global warming, and governmental action is overdue. At the just-concluded meeting of G8 nations, leaders agreed to further talks and possible actions related to global warming. Of course, it largely goes unmentioned that the necessary efforts to actually reduce carbon-dioxide emissions would result in draconian costs being imposed on U.S. businesses and consumers. Energy prices would soar, with economic output and jobs lost.

With such important questions under consideration, the Energy and Commerce Committee in the U.S. House of Representatives sought an independent source to sort matters out between the Mann, and the McKitrick and McIntyre camps. So, the committee turned to Dr. Edmund Wegman, a statistics professor at George Mason University, who also is the chairman of the National Academy of Sciences’ Committee on Applied and Theoretical Statistics and a board member of the American Statistical Association. He assembled a team including Dr. David Scott of Rice University and Dr. Yasmin Said at Johns Hopkins University. They worked pro bono and had no financial interest in the outcome.

The Wegman team found the Mann-led studies “to be somewhat obscure and incomplete,” and the McKitrick and McIntyre criticisms “to be valid and compelling.” They write: “Overall, our committee believes that Mann’s assessments that the decade of the 1990s was the hottest decade of the millennium and that 1998 was the hottest year of the millennium cannot be supported by his analysis.”

Does this mean that the global warming crowd will stop citing the now-discredited hockey stick graph? I seriously doubt it. Will they acknowledge that disagreement exists within the scientific community regarding man-made global warming? I doubt that as well. Why? Because this is more crusade than science.

In The Wall Street Journal on June 26, Richard S. Lindzen, the Alfred P. Sloan Professor of Atmospheric Science at MIT, wrote an important rebuttal to Gore’s film. The piece was straightforwardly titled “There Is No ‘Consensus’ on Global Warming.” Lindzen makes some key points worth noting here. First, he highlights the dynamic, changing nature of our climate:

“A general characteristic of Mr. Gore’s approach is to assiduously ignore the fact that the earth and its climate are dynamic; they are always changing even without any external forcing. To treat all change as something to fear is bad enough; to do so in order to exploit that fear is much worse. Regardless, these items are clearly not issues over which debate is ended — at least not in terms of the actual science.”

In conclusion, Lindzen ably sums up how the problem with the global warming advocates:

“First, nonscientists generally do not want to bother with understanding the science. Claims of consensus relieve policy types, environmental advocates and politicians of any need to do so. Such claims also serve to intimidate the public and even scientists — especially those outside the area of climate dynamics. Secondly, given that the question of human attribution largely cannot be resolved, its use in promoting visions of disaster constitutes nothing so much as a bait-and-switch scam. That is an inauspicious beginning to what Mr. Gore claims is not a political issue but a ‘moral’ crusade. Lastly, there is a clear attempt to establish truth not by scientific methods but by perpetual repetition.”

Apparently, sometimes the scientists don’t even understand the science, or at least the statistics. So, as disagreement continues to reign in the debate over global warming, at least one now has a couple of tools to check the veracity of those involved in the discussion. If they tout the hockey stick graph as completely valid and declare the science to be settled, then we must doubt their assertions in general on the topic of global warming.

Raymond J. Keating is chief economist for the Small Business & Entrepreneurship Council.