KYOTO, Japan _ The world's nations convened today for an extraordinary 10 days of negotiation over the planet's future, drawn together by a fear of global warming but divided over what to do about it.
Japan, chairman of the Climate Change Treaty talks, hoped to find a middle way forward through a thicket of technical and political disputes.
"These 10 days could change the history of mankind," Japan's foreign minister, Keizo Obuchi, said in welcoming the delegates from 150 countries. Japanese Environment Minister Hiroshi Ohki, the conference chief, pledged to "work hard to build consensus."
But success was far from guaranteed.
The pivotal disagreement focused on how much to rein in the industrial nations' emissions of carbon dioxide and other "greenhouse" gases linked to global warming. The United States, the biggest emitter, stood at the heart of the argument.
Under pressure from U.S. business leaders, the Clinton administration has proposed the most limited of several plans for mandatory cutbacks. The U.S. coal, oil and other industries say energy restraints would cost hundreds of thousands of American jobs.
This economic case represents, to one key figure here, a step forward from past arguments that global warming was an environmentalist fantasy.
"It's clear the more clever lobbyists have switched from criticizing the scientists to questioning how serious the impact would be on society," said Bert Bolin, the Swedish climate scientist who led an authoritative, nine-year U.N. review of the warming phenomenon.
A 1995 report by Bolin's network of more than 2,000 scientists helped spur world governments to take action. It cited a rise in global average temperatures of about 1 degree in the past century, and said manmade emissions were apparently at least partly to blame.
Carbon dioxide, nitrous oxide and other gases, mostly byproducts of the burning of fossil fuels, allow incoming sunlight to reach Earth but then trap the heat that Earth emits back to space.
The U.N. panel predicted even greater temperature rises in the 21st century, along with potentially damaging disruptions of climate patterns and rises in sea levels, as glaciers melt and oceans expand from warming.
In preliminary negotiations the past two years, diplomats have discussed strengthening the 1992 Climate Change Treaty, which set only voluntary goals for reducing emissions, by making cuts legally binding for 34 industrial nations.
The final talks here, for a "Kyoto Protocol" to the treaty, will culminate with three days of tough bargaining next week among high-level officials.
Some 1,500 delegates are taking part in the complex negotiations, observed by 3,500 representatives of environmental, business and other groups pushing favorite solutions to the energy dilemma _ from the Uranium Institute's advocacy of more nuclear power plants to Greenpeace's display of solar energy at work at an ancient temple site in this Japanese cultural capital.
In the end, the protocol is unlikely to do more than recommend ways to achieve mandated reductions. Individual governments will probably focus on converting power plants from coal-burning to more climate-friendly natural gas, developing more fuel-efficient automotive technology, and _ in Japan's case _ building more nuclear plants.
Some proposals on the table call for up to 20 percent cutbacks in emissions as early as 2005. The more modest U.S. plan envisions reducing industrial nations' carbon dioxide and other emissions only to, not below, 1990 levels by 2012.
President Clinton proposes accomplishing this in the United States largely through fiscal incentives for energy-saving technology, and by establishing a system for trading emissions "permits" among companies and countries.
American negotiator Melinda Kimble told delegates the U.S. plan represented a "steady, incremental approach." But environmentalists depicted Washington as the greatest obstacle to decisive early action to forestall global warming.
"Even as final negotiations get under way, it's not too late for the USA to come up with a more responsible position," said Lars Georg Jensen of the Worldwide Fund for Nature.
"Targets and timetables," as the cutback schemes are dubbed, will inevitably end up as just one more element in high-powered bargaining at Kyoto, as the industrial powers set an energy course for the 21st century.
In fact, the bidding began early as Kimble announced the United States, shifting position, was ready to consider limited "differentiation" of cutback targets _ that is, setting them at differing levels for individual countries based on national circumstances.
Some propose varying them according to per-capita, rather than gross, emissions. That would help an energy-efficient country like Japan while demanding more from the United States.
Other bargaining chips in play:
Delegations remain deadlocked over whether to count only the three most common greenhouse gases (carbon dioxide, methane and nitrous oxide) or to extend the cutbacks to others.
The United States wants developing countries to commit in some way to emissions cutbacks. The negotiations have exempted poor nations because they can little afford the cost of cutbacks, and the atmosphere's carbon accumulation is largely the product of the industrial North.