The Group of Eight leading nations agreed Tuesday to at least halve global carbon emissions by 2050, in what leaders hailed as a breakthrough but environmentalists called toothless.
After a night of tough negotiations in the Japanese mountain resort of Toyako, leaders of the world's eight most powerful economies agreed to toughen language on the most contentious issue among them.
President Bush had previously rejected any statement beyond saying that the major economies would "seriously consider" cuts in the greenhouse gas emissions blamed for heating up the planet.
The leaders of the G8 - Britain, Canada, France, Germany, Italy, Japan, Russia and the U.S. - said they shared a "vision" of reducing emissions by at least 50% by 2050.
But in a nod to Bush, the G8 leaders also called on major developing nations to join them in cutting emissions, something the U.S. leader has insisted is necessary.
"In our view, and in the view of the leaders in the room, this represents substantial progress from last year," Dan Price, Bush's assistant for international economic affairs, said.
The G8 nations also said they would each set their own interim targets for curbing greenhouse gas emissions for a still unspecified amount of time after the Kyoto Protocol's obligations expire in 2012.
"We acknowledge our leadership role, and each of us will implement ambitious economy-wide mid-term goals in order to achieve absolute emissions reductions," the joint statement said.
Japanese Prime Minister Yasuo Fukuda had pleaded for this year's summit not to backtrack on earlier pledges on global warming, which U.N. scientists warn could put entire species at risk unless it is curbed by later this century.
"It's been a long road getting here," Fukuda told reporters. "We had some very tough negotiations."
But he said the hard part wasn't over, with the G8 set to meet Wednesday in an extended session on climate change with leaders of major developing nations including China, India and Indonesia.
"This was a first step," Fukuda said. "Eventually, we have to find a framework in which everybody can participate."
But environmentalists said the progress was far too little to gloat about.
"If after a year's work, all you have is a 'shared vision' instead of 'seriously considering,' it's pretty pathetic," said Kim Carstensen, head of the World Wildlife Fund's Global Climate Initiative.
Daniel Mittler, a climate-change expert at Greenpeace International, said that "instead of action, the world got flowery words."
"The Texas oilman has once again prevented the G8 from undergoing the energy revolution it needs," Mittler said. "Bush is a lame duck, so who cares what he thinks about 2050?"
The U.S. is the only major industrial nation to shun the Kyoto Protocol. Bush argues that it is unfair, because it makes no demands of growing emerging economies such as China and India.
But both major candidates to succeed Bush, John McCain and Barack Obama, have pledged stronger action on global warming, including forcing domestic industry to cut emissions in the world's largest economy.
The U.S. and major developing countries agreed at a U.N.-backed conference in Bali in December to reach a new treaty by the end of 2009 for the post-Kyoto period starting in 2013.
Alden Meyer, policy director for the U.S.-based Union of Concerned Scientists, said that Bush was wrong to pressure China and India to do more on climate change.
"It wasn't China and India, it was the U.S. that had to be dragged kicking and screaming to the table in Bali," Meyer said. "So for President Bush to still be saying this is really arrogant."
Climate change has been the most contentious issue at the G8 summit, where leaders also are discussing African development and the political crisis in Zimbabwe.
The G8 leaders issued a statement warning that soaring oil and food prices pose a "serious challenge" to world economic growth and calling for boosted crude oil production capacity.
"The world economy is now facing uncertainty, and downside risks persist," the group said in a joint statement.