As delegates from more than 100 countries prepare to convene at the United Nations on Tuesday for the fifth and perhaps crucial negotiating session on a treaty to control global warming, the Bush administration is re-examining a position that until now has deadlocked the year-old talks.
In a flurry of discussions within the administration, officials are reconsidering the impact that a cap on emissions of carbon dioxide would have on the U.S. economy. Carbon dioxide is the chief heat-trapping gas that scientists fear will bring on a possibly catastrophic warming of the earth's climate.
The question of caps is central to the negotiations since the Europeans and the Japanese insist that carbon dioxide emissions in the industrialized countries be held to 1990 levels in the year 2000.
John H. Sununu, who as White House chief of staff made himself the decisive player on the issue, opposed such targets and timetables, and so, consequently, did the United States.
Sununu insisted that the prospect of serious global warming was too uncertain to risk a policy leading ultimately to big cutbacks in carbon dioxide emissions that could harm the nation's economy. The emissions are produced by the burning of fossil fuels like coal and oil on which the economy is largely based. By several accounts, Sununu throttled discussion of the matter. But he resigned in December.
Now pressure for a climate agreement is building both at home, in an election year, and abroad. All five major Democratic presidential candidates support caps on carbon dioxide emissions.
The administration's position on warming apparently has been undercut by recent scientific findings. And the Environmental Protection Agency has produced analyses indicating that the carbon dioxide cap proposed by the Europeans and Japanese might not be so costly to the United States. So the administration is taking another look.
Pressure is also being brought on behalf of the administration's present stance, however, by energy and energy-related industries.
Officials familiar with the discussions within the administration say that the situation is fluid and that no decision on any policy change has yet been made. Nor, they say, will any change materialize when the treaty talks begin today in New York.
The U.S. position paper for the opening of the session includes no reference to targets and timetables.
Rather, it calls for nations to take "cost-effective measures" to limit emissions of heat-trapping gases "in accordance with their national circumstances, development priorities and capabilities."
It is possible, some officials say, that a change in the U.S. position could take place before the New York session ends on Feb. 28. Otherwise it would have to surface, if at all, at a sixth session expected at the United Nations in April.
Environmentalists and some Europeans fear that this will not allow enough time to reach a meaningful convention on global warming that could be signed, as planned, at an "Earth Summit" dealing with a range of global environmental questions in Rio de Janeiro in early June.
"In April it may be too late," said Dr. Michael Oppenheimer, a climate specialist at the Environmental Defense Fund in New York. "We're not leaving enough time to build an intelligent agreement unless the U.S. switches its position during this negotiation."
If scientists are right, the stakes in the global warming talks are high. Carbon dioxide and other gases emitted as a result of human activity trap heat in the atmosphere much as glass panes trap it in a greenhouse.
Scientists convened by the United Nations to advise the negotiations predict that at present rates of emission, the buildup of greenhouse gases will increase the earth's average surface temperature by 3 to 8 degrees Fahrenheit by the end of the next century, with possibly catastrophic effects.
These could include a rise in sea level, a shifting of climatic and agricultural zones, more frequent droughts, and severe ecological disruption.