Researchers question key global-warming study
By Nick Schulz
SourceAn important new paper in the journal Energy & Environment upsets a key scientific claim about climate change. If it withstands scrutiny, the collective scientific understanding of recent global warming might need an overhaul.
A little background is needed to understand the importance of the new research behind this paper by Stephen McIntyre, a statistics expert who works in the mining industry, and Ross McKitrick, a professor of economics at the University of Guelph, Ontario. As scientists and governments have tried to understand mankind's influence on the environment, global warming has become a primary concern. Do mankind's activities -- especially burning fossil fuels to create energy -- affect climate? If so, how? What should be done?
These questions were so important that in 1988 the United Nations, along with the World Meteorological Organization, formed the U.N. Intergovernmental Panel on Climate Change (IPCC) to study ''human-induced climate change.''
Ten years after IPCC's founding, a paper from Michael Mann, now an assistant professor of environmental sciences at the University of Virginia, and his colleagues in the journal Nature shook scientific and political circles. It reconstructed temperatures dating back to the year 1400 by looking at tree rings, ice cores and other so-called proxy records to derive a temperature signature. This was before the sophisticated climate-measuring equipment we use today.
What Mann claimed to find was startling: The late-20th century was unusually warm -- warmer than at any time in the previous six centuries. (Later research by Mann extended the climate history back 1,000 years.) The reason? ''It really looks like (the recent warming) can only be explained by greenhouse gases,'' Mann said then. His clear implication: The Earth's climate was changing dramatically, and mankind was responsible.
Earth heats up?
The U.N. used Mann's research to declare the 1990s ''the warmest decade and 1998 the warmest year of the millennium.'' Countless news stories picked up on this idea that the past few years have been unusually warm.
Efforts to limit the emission of the greenhouse gases blamed for this warming were bolstered by Mann's research. In fact, this week the Senate plans to consider legislation co-sponsored by Sens. John McCain, R-Ariz., and Joe Lieberman, D-Conn., to reduce the emission of greenhouse gases. McCain's Web site says, ''Global warming is a growing problem. . . . The 10 warmest years (on record) have all occurred since 1987.'' The statement is based on Mann's research.
But what if it's not true?
When McIntyre and McKitrick audited Mann's data to see whether its conclusions could be replicated, they discovered significant problems. Once they corrected the errors, the two researchers made a remarkable conclusion: The late 20th century was not unusually warm by historical standards.
Not alone in his conclusion
When asked about the paper, which had undergone review by other scientists before being published, Mann said he had heard about it but had not seen it. He called it a ''political stunt'' and said ''dozens of independent studies published by leading journals'' had come to conclusions similar to his.
What's to guarantee McKitrick and McIntyre's research will withstand the kind of scrutiny they gave Mann's research?
In an interview, McKitrick said, ''If a study is going to be the basis for a major policy decision, then the original data must be disseminated and the results have to be reproducible. That's why in our case we have posted everything online and invite outside scrutiny.''
Mann never made his data available online -- nor did many of the earlier researchers whose data Mann relied upon for his research. That by itself raises questions about the U.N. climate-change panel's scientific process.
It remains to be seen whether the McKitrick and McIntyre study will withstand the ''outside scrutiny'' they have asked for and will no doubt receive. But given the implications of the errors and problems they apparently have unearthed within the Mann study, the two researchers have done a tremendous service to science and the public, which should rely on facts to make informed public policy decisions.
Nick Schulz is editor of TechCentralStation.com, a science, technology and public policy Web site.