Science: Fighting over a hockey stick
For years, climate scientists and global warming skeptics have been battling over a deceptively simple chart. Now, an influential congressman's unusual request is stirring up yet more controversy.
Based on modern measurements, historical records, and data garnered from climate "proxies" such as tree rings and ice cores, the graph of global temperature has earned the nickname "the hockey stick" for its shape—relatively flat for most of the past millennium (the handle), with a sharp uptick—representing a hotter planet—over the past century (the blade). First introduced by three American researchers in a 1998 Nature paper ["Global-scale temperature patterns and climate forcing over the past six centuries," figure 5.b], the graph was incorporated into an influential 2001 report by the Intergovernmental Panel on Climate Change (IPCC), which concluded that Earth is warming and that human activities such as burning fossil fuels to produce greenhouse gases are the likely cause.
The hockey stick quickly became a favorite target for critics of that conclusion. Most recently, on June 23, Rep. Joe Barton, a Texas Republican and chairman of the Energy and Commerce Committee, sent letters to the three researchers, as well as to the IPCC and the National Science Foundation (NSF). In the letters, Barton, a noted opponent of caps on greenhouse gas emissions, cites the work of global-warming skeptics and requests reams of information about the scientists' careers, methodologies, data, and funding—all due by July 11.
Many scientists were horrified by Barton's unusual request. The European Geosciences Union, for example, called the letters "burdensome and intrusive" and "highly inappropriate." Most of the requested information is already available on the Web, climate scientists note, and the work in question has been thoroughly checked, replicated, and extended in the normal course of scientific inquiry. Some researchers even speculated that Barton's letters are an attempt to intimidate global-warming researchers.
Not so, says a committee spokeswoman. The committee has been in touch with all five recipients, she says, and is working with them to get the requested material, all in the interest of ensuring data quality.
"We need to make sure that [the data] Congress is using to formulate policy is based on the best information possible," the spokeswoman says.
That shouldn't be a problem. Despite constant sniping in minor research journals and on conservative editorial pages, the science underlying global warming—including the hockey stick, which is just one of several lines of evidence—has remained remarkably robust. (Climate researchers, including two authors of the original hockey stick paper, refute what they see as politically motivated attacks on mainstream climate science at realclimate.org.) And the linkages between humans and a warming Earth have grown strong enough for the heads of 11 national academies of science to issue a joint statement in June ["Global response to climate change"], warning that "climate change is real" and urging prompt international action to reduce the effect on humans. Seeking out the best available data is always an admirable goal. In this case, climate scientists are confident that Barton already has it.
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