U.S. Report Turns Focus to Greenhouse Gases


By ANDREW C. REVKIN

Published: August 26, 2004



In a striking shift in the way the Bush administration has portrayed the science of climate change, a new report to Congress focuses on federal research indicating that emissions of carbon dioxide and other heat-trapping gases are the only likely explanation for global warming over the last three decades.

In delivering the report to Congress yesterday, an administration official, Dr. James R Mahoney, said it reflected "the best possible scientific information" on climate change. Previously, President Bush and other officials had emphasized uncertainties in understanding the causes and consequences of warming as a reason for rejecting binding restrictions on heat-trapping gases.

The report is among those submitted regularly to Congress as a summary of recent and planned federal research on shifting global conditions of all sorts. It also says the accumulating emissions pose newly identified risks to farmers, citing studies showing that carbon dioxide promotes the growth of invasive weeds far more than it stimulates crops and that it reduces the nutritional value of some rangeland grasses.

American and international panels of experts concluded as early as 2001 that smokestack and tailpipe discharges of heat-trapping gases were the most likely cause of recent global warming. But the White House had disputed those conclusions.

The last time the administration issued a document suggesting that global warming had a human cause and posed big risks was in June 2002, in a submission to the United Nations under a climate treaty. President Bush distanced himself from it, saying it was something "put out by the bureaucracy."

That may be harder to do this time. The new report, online at www.climatescience.gov, is accompanied by a letter signed by Mr. Bush's secretaries of energy and commerce and his science adviser.

The White House declined yesterday to explain the change in emphasis, referring reporters to Dr. Mahoney, assistant secretary of commerce for oceans and atmosphere and the director of government climate research.

In an interview, he said the report was mainly an update on the overall climate research program and was not intended to be a conclusive "state of the science'' summary of the administration's thinking. A series of 21 reports are promised on particular issues in coming years, he said, and the studies on climate models, agriculture and other subjects mentioned in the new report are "significant but not definitive.''