for National Geographic News
Tomorrow the United Nations-backed Intergovernmental Panel on Climate Change (IPCC) will release a major report with grim predictions about global warming for the coming decades, according to journalists who have seen draft versions of the paper.
If the IPCC's recent track record is any indication, the predictions will be no exaggeration, an analysis posted today on the Web site of the journal Science suggests.
The Science study compared actual climate measurements with the computer models from a 2001 IPCC report.
In recent years actual concentrations of carbon dioxide—a greenhouse gas linked to global warming—have followed almost exactly the projections of the 2001 IPCC report.
If anything, the IPCC may have underestimated some climate threats in 2001. For example, actual temperatures were at the high end of the predicted range. And sea levels have actually risen faster than predicted.
"The real climate system is changing as fast or in some components even faster than expected by [the] IPCC," Stefan Rahmstorf, an ocean physicist at Potsdam University in Germany, said by email.
Rahmstorf is the Science study's lead author. He is also among the scientists gathered in Paris to finalize the IPCC's 2007 assessment report.
Friday's study will be the fourth report compiled by the IPCC since the United Nations and World Meteorological Organization established the panel in 1988. Hundreds of scientists contribute to each report.
Richard Alley is a glaciologist at Pennsylvania State University who was not involved in the Science study but is an IPCC report author.
The study vindicating the 2001 report is "great and important," Alley said in an email from Paris.
"There has long been a muttering, out in the blogosphere and other places, that the scientists have been exaggerating and trying to scare people so as to generate more research money," he said.
"If you wish to accuse scientists of systematic error, Rahmstorf et al show that we have been a bit conservative, and clearly not alarmist," Alley added.
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