WASHINGTON–January 29, 2007–Later this week, international climate scientists will issue a dire forecast for the planet that warns of slowly rising sea levels and higher temperatures. But that may be the sugarcoated version.
Early drafts of their upcoming report on climate change foresee smaller sea level rises than were projected in 2001 in the last report. Many top US scientists reject these rosier numbers. Those calculations don’t include the recent, and dramatic, melt-off of big ice sheets in two crucial locations:
They “don’t take into account the gorillas–Greenland and Antarctica,” said Ohio State University earth sciences professor Lonnie Thompson, a polar ice specialist. “I think there are unpleasant surprises as we move into the 21st century.”
Michael MacCracken, who until 2001 coordinated the official US government reviews of the international climate report on global warming, has fired off a letter of protest over the omission.
The melting ice sheets in Greenland and Antarctica are a fairly recent development that has taken scientists by surprise. They don’t know how to forecast its effects in their computer models. But many fear it means that the world’s coastlines will be swamped much earlier than most predict.
Others believe the ice melt is temporary and won’t play such a dramatic role.
That debate may be the central one as scientists and bureaucrats from around the world gather in Paris to finish the first of four major global warming reports by the Intergovernmental Panel on Climate Change. The panel was created by the United Nations in 1988.
After four days of secret editing, the final report will be issued Friday.
The early versions of the report predict that by 2100 the sea level will rise between 5 and 23 inches. That is far lower than the 20 to 55 inches forecast by 2100 in a study published in the peer review journal Science this month. Other climate scientists, including NASA’s James Hansen, predict a sea level rise that can be measured by feet more than inches.
The report is also expected to include some kind of proviso that says things could be much worse if ice sheets continue to melt.
The prediction being considered this week by the IPCC is “obviously not the full story because ice sheet decay is something we cannot model right now, but we know it’s happening,” said Stefan Rahmstorf, a climate panel lead author from Germany who made the larger prediction of up to 55 inches of sea level rise. “A document like that tends to underestimate the risk,” he said.
“This will dominate their discussion because there’s so much contentiousness about it,” said Bob Corell, chairman of Arctic Climate Impact Assessment, a multinational research effort. “If the IPCC comes out with significantly less than one meter [about 39 inches of sea level rise], there will be people in the science community saying we don’t think that’s a fair reflection of what we know.”
There are questions about how permanent the melting in Greenland and Antarctica are, said panel lead author Kevin Trenberth of the National Center for Atmospheric Research in Colorado.