The international agreement was adopted last December in Kyoto, Japan. It commits developed nations to reducing their collective emissions of six key greenhouse gases to about 5 percent below 1990 levels. The goals must be reached by 2012, and ``demonstrable progress'' must be made by 2005.
The pact does not specify how nations are to accomplish that, but some measures could include introducing cleaner-burning power plants and automobiles, making appliances more efficient, and planting more trees (which take in carbon dioxide).
The United States, the world's biggest polluter, would be required to reduce its emissions of carbon dioxide and other gases by more than the average; it would have to cut them by 7 percent. The nation is headed in the opposite direction: Estimates indicate that U.S. emissions will be 12 percent higher in 2000 than in 1990.
Opponents of the treaty criticized the administration's signing of the agreement yesterday, while environmentalists said the action was tardy and largely symbolic. Peter Burleigh, acting U.S. ambassador to the United Nations, signed the document at U.N. headquarters in New York. Yesterday was the next-to-last day of an 11-day international conference on climate change being held in Buenos Aires, Argentina.
Vice President Gore, who has led the administration's efforts to reduce greenhouse-gas emissions, said yesterday that ``evidence of global warming has grown only stronger'' since the Kyoto agreement was reached 11 months ago. He said the signing ``underscores our determination to achieve a truly global solution to this global challenge.''
But Gore noted that the signing ``imposes no obligations on the United States,'' and he said the administration would not submit the treaty to the Senate ``without the meaningful participation of key developing countries.''
At issue are the emissions of gases, especially carbon dioxide, that are produced by the burning of fossil fuels in factories and vehicles. These gases let in sunlight, but tend to insulate the planet against the loss of heat, like the glass of a greenhouse. A higher concentration, therefore, means a warmer climate.
The Earth's global average temperature has increased by about one degree over the last century. Current projections are that the global average temperature will rise an additional 2 to 6 degrees by 2100.
In 1992, the United States and 160 other nations meeting in Rio de Janeiro, Brazil, agreed to stabilize atmospheric concentrations of greenhouse gases at levels that would ``prevent dangerous [man-made] interference with the climate system.'' The Kyoto Protocol is an effort to enforce the Rio Convention by setting binding emissions reductions.
How much temperatures will rise and how the increases will affect the environment remain subjects of intense debate. The administration's predictions have included rising seas, increased flooding and droughts, and more severe weather. Skeptics have argued that warming could actually benefit agriculture and reduce weather severity.
Speaking from Buenos Aires, Philip E. Clapp, president of the National Environmental Trust, criticized the signing as too little, too late.
``The U.S. has signaled it is not willing to lead on this issue,'' Clapp said. ``Coming just 24 hours before the end of the meetings here, it is too late to have any impact. Because of the Clinton administration's inaction, talks here have ground to a stalemate.''
Clapp accused Gore of trying to placate powerful American industries because of his likely presidential bid in 2000.
The oil industry was just as quick to criticize the signing as a ``mistake.'' The American Petroleum Institute said the agreement ``would do little to reduce carbon dioxide concentrations while imposing unacceptable costs on the pocketbooks of American consumers.''
The Kyoto Protocol commits most European nations to cuts of 8 percent below 1990 levels, and Canada, Hungary, Poland and Japan to 6 percent. Russia, New Zealand and Ukraine are to stabilize emissions at 1990 levels, while Norway may increase emissions by up to 1 percent.