The nations of the world will meet in Montreal this week to start discussing the next step in combating the global warming problem, hoping to devise a successor to the Kyoto Protocol that was scorned by the Bush administration in 2001. But the United States is saying it doesn't want to talk.

Despite the Bush administration's resistance, an assortment of U.S. elected officials, industry representatives and environmentalists are pushing to chart a new climate change strategy that will bring the United States back into international discussions while forcing developing countries to make meaningful cuts in their own carbon dioxide emissions. This push for a more flexible approach than Kyoto provided will be on full display in Montreal and could frame how the world confronts climate change in the years to come.

"Most people are ready to take the dialogue forward. The only place where that is not the case is the administration," said Eileen Claussen, president of the Pew Center on Global Climate Change. Many advocates, analysts and policymakers are willing to move beyond the "one size fits all" approach of Kyoto, she added.

Climate experts such as Claussen are grappling with how best to proceed after 2012, when Kyoto -- which set a goal of cutting heat-trapping gases by 7 percent below 1990 levels by then -- expires. Scientists such as Princeton University's Michael Oppenheimer believe the world is in the middle of "the critical decade" in terms of curbing greenhouse gas emissions and needs to lock in carbon dioxide cuts soon before the warming trend has irreversible consequences.

"We do have a little time, but not much. . . . If we don't get a serious program in place for the long term in this second post-Kyoto phase, we will simply not make it and we will be crossing limits which will basically produce impacts that are unacceptable," Oppenheimer told reporters in a telephone conference call this month.

Starting tomorrow and continuing until Dec. 9, two overlapping groups will be meeting in Montreal: the 156 countries that signed Kyoto, which include every industrialized nation except the United States and Australia; and the 189 signatories to the 1992 U.N. Framework Convention on Climate Change, a pact without binding emissions limits that the United States and Australia have both endorsed.

Negotiators are hoping to have talks about a post-Kyoto climate strategy under the auspices of the U.N. Framework Convention, the broader coalition. But Paula J. Dobriansky, the undersecretary of state for democracy and global affairs, said the United States would prefer that each country to pursue its own way of curbing harmful emissions.

"We don't see the commencement of a negotiation process as contributing to progress now . . . given the differing positions held by parties to the Framework Convention on Climate Change," she said. "One of the best ways forward is to allow for the development of different approaches."

The Bush administration has spent $20 billion on climate change programs since taking office, Dobriansky added, and cut greenhouse gas emissions by 0.8 percent between 2000 and 2003. "The United States is taking leadership here," she said, adding that it also is engaged in bilateral and regional climate talks.

Environmentalists are pressing negotiators in Montreal to begin sketching out a future climate strategy without the United States, leaving room for it to come aboard later. David Doniger, Climate Center policy director at the Natural Resources Defense Council, compared it to the launching of a ship in which other negotiators "want to reserve a stateroom" for the United States: "They would make a big mistake if they waited for the U.S. to get aboard."

Sharon Lee Smith, director general for policy at Environment Canada and one of the nation's lead delegates, said organizers want as many countries as possible to engage in post-Kyoto talks but will proceed even without the United States.

"There is a view Montreal is the time to talk about the future in more detail," Smith said. "We'll be pushing ahead."

Some advocates are trying to jump-start the process by outlining a different approach to cutting carbon dioxide emissions than is spelled out in Kyoto. Earlier this month the Pew Center joined with the World Economic Forum, a Geneva-based group of international business and political leaders, in releasing a novel plan based on 18 months of discussions with policymakers, industry officials and environmental activists from around the world. This proposal would seek to have each industrial sector agree on a global emissions limit and require developing nations to commit to a specific target for increasing reliance on renewable energy sources, either collectively or individually.

"We were trying to come up with something that was meaningful but with maximum flexibility," Claussen said.

The two top senators on the Foreign Relations Committee, Richard G. Lugar (R-Ind.) and Joseph R. Biden Jr. (D-Del.), have endorsed the Pew proposal and introduced a resolution calling for the United States to take a more active role in climate negotiations.

"It's critical that the international dialogue on climate change and American participation in those discussions move beyond the disputes over the Kyoto Protocols," Lugar said.

Several political leaders on the state and local levels are also pushing for more aggressive action.

Democratic Govs. Janet Napolitano (Ariz.) and Bill Richardson (N.M.) have agreed on a regional climate pact to try to cut greenhouse gas emissions. Nine Northeastern states are hoping to launch a carbon dioxide emissions trading system next month, and California, Oregon and Washington are discussing a similar venture to lower the region's contribution. Mayors of 188 cities have pledged to cut their greenhouse gas emissions by about 7 percent; Salt Lake City is three-quarters of the way there.

"We're not waiting for the Congress or the administration to set policy because there's such a leadership vacuum," said Richardson, who will attend the Montreal talks or send a delegate. "States are going to take matters in their own hands. This is a serious problem that requires immediate action."

Many major U.S. companies are also responding to Kyoto. Pharmaceutical giant Johnson & Johnson pledged two years ago to cut its 1990 greenhouse gas emissions by 7 percent by 2010. So far it has cut them 3.1 percent despite growing fourfold in size during that period.

"We feel climate change is very real," said Johnson & Johnson executive director of energy management Dennis Canavan, who will attend the Montreal talks unofficially. "We want to make sure we minimize our impact on that."

At the same time, some developing countries that had resisted the idea of greenhouse gas limits have been showing a greater willingness to participate in climate talks. Brazil plans to announce in Montreal that it reduced its rate of deforestation by 40 percent between August 2004 and August 2005, according to several sources, which is significant because deforestation accounts for 80 percent of the country's greenhouse gas emissions. Other developing nations, such as Mexico, have suggested they are more open to adopting emission curbs.

Michael Zammit Cutajar, Malta's ambassador for international environmental affairs who helped oversee global climate accords between 1992 and 2002, said developing countries "are prepared to look beyond their current situation as well," provided they get a positive signal from industrialized nations.

This kind of analysis worries Kyoto critics such as Roy Spencer, a research scientist at the University of Alabama at Huntsville who does not believe the climate will warm as rapidly as many computer models predict.

"Asking people to cut their energy use is like asking people to stop eating," said Spencer, who contributes to the free-market online journal Tech Central Station, which is in part funded by oil companies opposed to mandatory carbon limits. "The solution is in technology."

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