Humans Faulted for Global Warming

The authors concluded that Earth's average temperature will increase between 3.2 and 7.8 degrees Fahrenheit over the next century, while sea levels will rise between seven and 23 inches.

IPCC scientists also said that global warming will not trigger a shutdown within the next 100 years of the North Atlantic ocean current that keeps Northern Europe temperate, though they do not predict whether it might occur in future centuries. In a similar vein, the authors said they did not have sophisticated enough computer models to project how much melting of the Greenland ice sheet would boost sea levels over the next century, but they suggested that over several centuries the ice sheet's disappearance could raise sea levels by a devastating 23 feet.

Bush administration officials said yesterday that they welcomed the report and emphasized that U.S. research funding helped underpin its conclusions. National Oceanic and Atmospheric Administration Administrator Conrad C. Lautenbacher Jr., who oversees much of the nation's climate research, said in an interview that the international assessment will lead to "a more objective and informative public debate."

But environmental advocates said the White House -- which remains opposed to mandatory limits on U.S. carbon emissions -- is making a mistake in assuming research and technological advances alone will address global warming.

"The administration's proposals are at least a decade away," said Angela Anderson, vice president for climate programs at the National Environmental Trust. "The promise of better technologies tomorrow shouldn't stop us from doing what we can today."

House and Senate Democratic leaders back a cap on greenhouse gases and hope to enact such legislation this year; next week, several of the report's authors are to testify in congressional hearings.

In an interview yesterday, House Science and Technology Committee Chairman Bart Gordon (D-Tenn.) called the report "a unanimous, definitive world statement" on climate change that, if anything, was too conservative. "It's time to end the debate and act," Gordon said. "All the naysayers should step aside."

Some critics, however, question the push for nationwide limits on emissions from power plants, automobiles and other industrial sources. At the George C. Marshall Institute, a think tank that receives funding from Exxon Mobil, chief executive William O'Keefe and President Jeff Kueter issued a statement urging "great caution in reading too much" into the report until the panel releases its detailed scientific documentation a few months from now.

"Claims being made that a climate catastrophe later this century is more certain are unjustified," they said, adding that "the underlying state of knowledge does not justify scare tactics or provide sufficient support for proposals . . . to suppress energy use and impose large economic burdens on the U.S. economy."