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'Hockey Stick' model of global warming theory is broken
By Cheryl Stubbendieck
Nebraska Farm Bureau Federation
Scientists who aren't convinced by the global warming theory are throwing a well-aimed wrench into the "hockey stick model" of historic climate trends.
In mid-July, the National Center for Policy Analysis issued a report that exposes serious problems with the climate trends reconstruction published by the United Nations' Intergovernmental Panel on Climate Change.
That reconstruction is the primary evidence used by policy makers and activists who espouse the theory that human activity is causing catastrophic global warming. The UN report contends that industrialization put carbon dioxide and other greenhouse gases into the atmosphere, leading to increasing global air temperatures. The UN panel also claimed that the 1990s were the warmest decade of the last thousand years and 1998 was the warmest year.
"The (UN panel) claims that human activities are responsible for nearly all the earth's recorded warming during the past two centuries," says David Legates, author of the policy center's analysis and director of the Center for Climatic Research at the University of Delaware. "Yet the primary assessment they use as support appears to be more junk science than solid evidence."
At issue, Legates says, is what is professionally referred to as the "hockey stick"--a widely circulated image that depicts a 700-year period where temperatures remained relatively constant, followed by the last 100-plus years where temperatures have shot upwards. The "hockey stick," developed by researchers Michael Mann of th University of Virginia and Phil Jones of the University of East Anglia, is used by the UN panel and environmental activists as proof of human-induced global warming.
The Policy Analysis Center's report cites findings from five independent research groups that have uncovered serious problems with the methodology and calculations of the hockey stick model, which raises questions about the validity of any of its conclusions.
The report concludes that researchers made errors in the collection and use of varying data from multiple sources, used obsolete data, made incorrect calculations, associated data sets with incorrect geographical locations, and employed statistical methods that removed long time period trends, such as the widely recognized Medieval Warm Period (about A.D. 800 to 1400) and the Little Ice Age (A.D. 1600 to 1850).
In June, Michael Mann published a retraction in "Geophysical Research" journal, in which he admitted underestimating temperature variations by more than one-third since 1400--which would explain his missing the 250-year-long Little Ice Age. Still he argues that that significant error doesn't affect his conclusions.
Legates and his colleagues found that the "blade" portion of the hockey stick model, showing a sudden rise in temperature during the last hundred or so years, couldn't be reproduced using common statistical techniques--or even using the same techniques as Mann used.
Legates concludes, understandably, that the hockey stick is broken and shouldn't be used as the basis for policy decisions on climate issues. The UN needs to take another look at its conclusions and a very close look at the methods used by its researchers.
Date: 7/21/04
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