The New York Times,Aug. 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.''
Still, the report was disputed by some groups, aligned with industry, that oppose restrictions on carbon dioxide emissions and have attacked science pointing to dangerous human-caused warming as flawed.
Myron Ebell of the libertarian Competitive Enterprise Institute said the report was "another indication that the administration continues to be incoherent in its global warming policies."
At the same time, the report did not please environmental groups, which have repeatedly criticized Mr. Bush for opposing efforts to require restrictions on the gases linked to global warming, though he has gradually come around to the position that warming is at least partly caused by emissions.
"The Bush administration on the one hand isn't doing anything about the problem, but on the other hand can't deny the growing science behind global warming," said Jeremy Symons of the National Wildlife Federation.
The studies in the report that point to a human cause for recent warming all involved supercomputer simulations of climate, which have increased in power over the last several years.
The latest analysis, done at the National Center for Atmospheric Research in Boulder, Colo., found that natural shifts in the output of the sun and other factors were responsible for the warming from 1900 to 1950, but could not explain the sharp and continuing rise since 1970.
The report's section on agriculture focused on several studies in which fields and grasslands were exposed to doubled concentrations of carbon dioxide, with growth patterns in plants shifting in ways that could harm yields.
In such conditions, it said, plots of shortgrass prairie in northeastern Colorado contained less of the nutrient nitrogen, and their grasses were less digestible than those that grew with no extra carbon dioxide.
"In another experiment, increased CO2 stimulated the growth of five of the most important species of invasive weeds, more than any other plant species yet studied," the report said. "This suggests that some weeds could become bigger problems as CO2 increases."