A global-warming brouhaha has critics of a landmark climate report saying the 20th century was not as hot as it was cracked up to be.
Climate scientists, who have long been raising red flags on the impact modern man is having on Earth’s climate, are calling the critics half-baked.
The debate – the subject of a briefing Tuesday on Capitol Hill – highlights the opposing arguments in the global-warming controversy.
On one side are researchers concerned about temperature-raising pollutants. On the other are those concerned that this is an over blown argument that will stall economic progress.
At issue is a 1998 study in the journal Nature that described the 20th century as the hottest in centuries. Similar warnings from an influential United Nations science panel echoed that report.
Climate research has been an increasingly politicized issue since 2001, when President Bush rejected a multination plan crafted in Kyoto, Japan, to combat global warming. Bush cited the costs of capping emissions of greenhouse gases produced by burning fossil fuels such as coal and petroleum.
In a paper published last month in Energy & Environment, a social science journal known for reports critical of climate-change research, Canadian businessman Stephen McIntyre and economist Ross McKitrick of Canada’s University of Guelph charge that the Nature report contains numerous errors regarding temperatures from the past six centuries.
When corrected, the data suggest the 15th century was actually warmer than today, they say.
They also criticize the U.N. panel for relying on the Nature study in its warnings about global warming. In 2001, the U.N.’s Intergovernmental Panel on Climate Change said the average surface temperature rose 1 degree during the 20th century and could rise 2.6 to 10.4 degrees this century, partly driven by industrial activities that emit greenhouse gases. (Related document: The IPCC 2001 report on climate science)
“Unfortunately, a lot was made of the Nature paper, so ordinary debate about its technical soundness takes on inordinate political overtones,” says McKitrick.
The George C. Marshall Institute, one of a number of think tanks that question the human role in global warming, sponsored a briefing Tuesday for congressional staffers and others on the rebuttal report.
The authors of the Nature paper, led by climatologist Michael Mann of the University of Virginia, respond that the critics botched their analysis, selectively dropping records to invent a warm 15th century and making numerous other statistical mistakes.
Climate researcher Tom Wigley of the National Center for Atmospheric Research. in Boulder, Colo., calls the critics’ complaints “seriously flawed” and “silly.”
In addition to the Nature paper, about a dozen independent studies suggest the 20th century was warmer than normal, Wigley points out.
From a statistical viewpoint, “I lean in favor of Mann,” says statistician George Shambaugh. of Georgetown University. “There is an increase in the 20th century that is greater than the cyclical patterns found by either group since 1550. And since the early 1900s, we have been hotter than any time since then.”
Princeton geoscientist Michael Oppenheimer. compares climate skeptics to tobacco industry scientists who sought for decades to obscure the link between smoking and lung cancer. Arguing over whether man-made global warming exists obscures a more important debate over what steps are possible to moderate its effects, he says.
But skeptics are providing a valuable public service in keeping the debate alive, says William O’Keefe of the Marshall Institute. O’Keefe, formerly with the American Petroleum Institute, says: “We have to encourage healthy debate.”
This article appeared USA TODAY on November 18, 2003 at http://www.usatoday.com/weather/climate/2003-11-18-warming-debate_x.htm