The Group of Eight industrialized nations joined with developing countries in agreeing Wednesday that average global temperatures shouldn't increase by more than 2 degrees Celsius in a significant new acknowledgement in the fight against global warming.
President Barack Obama and other G-8 leaders also said they supported a goal of reducing greenhouse gas emissions by 80 percent or more by 2050. But they made no nearer-term reduction targets and 17 developing nations participating in the G-8 summit refused to commit to any targets at all, disappointing environmentalists.
Most scientists agree that even a slight increase in average temperatures will wreak havoc on farmers around the globe, as seasons shift, crops fail and storms and droughts ravage fields.
Climate-change experts said the acknowledgment on the 2 degree temperature cap from both the G-8 and the developing nations was an important step since it now implies that countries actually have to do something to prevent temperatures from increasing. But they chastised the G-8 for not giving any indication of how they plan to do it.
"What are they going to do between now and 2020?" asked Kim Carstensen of the World Wild Fund for Nature. "If they don't outline a path to reach the announced goal, the 2 degree statement will just join a long list of broken promises."
British Prime Minister Gordon Brown called it a "historic agreement" and German Chancellor Angela Merkel said it was "a clear step forward."
"After a long struggle, all of the G-8 nations have finally accepted the 2-degree goal. From the United States of America to Japan and Europe, everyone will work on this goal," Merkel told reporters.
The leaders reached agreement on the first day of the G-8 summit, which opened with the leaders of the United States, Britain France, Italy, Germany and Japan discussing a host of issues, from climate change to the financial crisis to North Korean nuclear nonproliferation.
They will be joined Thursday for a deeper discussion on climate change with the 17-member Major Economies Forum, which includes China, which has overtaken the U.S. as the world's biggest polluter, and India, which is close behind. Mexico, Brazil, South Africa, Indonesia, Australia, South Korea and the European Union also are in that club of the world's major polluters.
The climate discussions at L'Aquila come ahead of a crucial December summit in Copenhagen, Denmark, where the United Nations aims to conclude a new, worldwide climate pact to replace the 1987 Kyoto protocol.
In their statement Wednesday, the G-8 said there was a "broad scientific view" that global temperatures "ought not to exceed 2 degrees Celsius" from their pre-industrial levels.
The forum of developing countries used the same language in their provisional statement. The forum countries, though, made no emissions reductions targets in their statement, scrapping any reference to it because the G-8 wouldn't agree to nearer-term goals which they think are more important.
U.N. scientists have said keeping the rise in temperature within safe limits means the world must halve heat-causing pollution by mid-century. Until now, the U.S. has resisted embracing the 2-degree C target because it implies a commitment to dramatically change the way the world generates electricity, fuels its cars and builds its houses.
"This limit commits the G-8 to follow the science, which is good," said Antonio Hill, Oxfam spokesman. "But 2050 is too far off to matter. Poor people are being hit today."
Alden Meyer, of the Union of Concerned Scientists, said early drafts of the developing countries statements had included language pledging a 50 percent global reduction in emissions by 2050 and 80 percent reduction by industrialized countries. But the emerging countries said in their provisional statement only that they would work together to achieve "strong results" on emissions reductions before the Copenhagen summit, without committing to any numbers.
They did, however, say they would take actions that "represent a meaningful deviation from business as usual in the mid-term" — more of a commitment than they have previously been willing to make.
The emerging countries have been upset that the industrialized G-8 hasn't been forthcoming on either mid-term emissions reductions or pledges of financing and transferring technology to the developing world, and are refusing to commit to specific targets until financing commitments are made by the G-8.
A panel of U.N. scientists has said industrial countries must together cut carbon emissions by 25 percent to 40 percent from 1990 levels by 2020 to keep average global temperatures from rising more than 2 degrees above preindustrial levels 150 years ago.
At their last summit in Japan a year ago, the G-8 committed to reducing global carbon emissions 50 percent by 2050. But did not specify their own responsibility, as they did on Wednesday.
The G-8 said its members could use as the baseline 1990 or a more recent year — a compromise between Europeans who sought the 1990 benchmark and the United States and Japan who have used 2005 in their calculations.
The difference is significant: Since 1990, U.S. emissions have risen 23 percent.