COPENHAGEN -- Delegates converged Sunday for the grand finale of two years of tough, sometimes bitter negotiations on a climate change treaty, as U.N. officials calculated that pledges offered in the last few weeks to reduce greenhouse gases put the world within reach of keeping global warming under control.
Yvo de Boer, the U.N.'s top climate official, said on the eve of the 192-nation conference that despite unprecedented unity and concessions, industrial countries and emerging nations need to dig deeper.
Finance _ billions of dollars immediately and hundreds of billions of dollars annually within a decade _ was emerging as the key to unblocking an agreement that would bind the global community to a sweeping plan to combat climate change.
"Time is up," said Yvo de Boer, the top U.N. climate official.
"Over the next two weeks governments have to deliver" with larger emission reduction commitments and specific financial pledges for poor countries to help them adapt to changing climate and to shift to low-carbon economic expansion, de Boer told reporters in advance of Monday's opening.
South Africa on Sunday became the latest country to announce an emissions target. It said over the next 10 years it would reduce emissions by 34 percent from "business as usual," the level they would reach under ordinary circumstances. By 2025 that figure would peak at 42 percent, effectively leveling off and thereafter begin to decline.
"This makes South Africa one of the stars of the negotiations," said the environmental group Greenpeace.
President Barack Obama's decision to attend the conclusion of the two-week conference, coming after phone consultations with other heads of state, was taken as a signal that an agreement was getting closer. He originally planned to make a five-hour stop in the Danish capital this week.
More than 100 heads of state and government have said they will attend the last day or two, making Copenhagen the largest and most important summit on climate ever held.
"Never in the 17 years of climate negotiations have so many different nations made so many firm pledges together," De Boer said. "It's simply unprecedented."
A study released by the U.N. Environment Program Sunday indicated that pledges by industrial countries and major emerging nations fall just short the reductions of greenhouse gas emissions that scientists have called for _ and the gap is narrower than previously believed.
"For those who claim a deal in Copenhagen is impossible, they are simply wrong," said UNEP director Achim Steiner, releasing the report compiled by British economist Lord Nicholas Stern and the Grantham Research Institute.
Environmentalists have warned that emissions commitments were dangerously short of what U.N. scientists have said were needed to keep average temperatures from rising more than 2 degrees C (3.6F) above what the industrial age began 250 years ago.
But most of those warnings were based on pledges only from industrial countries. The UNEP report included pledges from China and other rapidly developing countries, which in turn were contingent on rich-country funding to help.
UNEP said all countries together should emit no more than 44 billion tons of carbon dioxide by 2020 to avoid the worst consequences of a warming world.
Computing the high end of all commitments publicly announced so far, the report said emissions will total some 46 billion tons annually in 2020. Emissions today are about 47 billion tons.
"We are within a few gigatons of having a deal," Steiner said. "The gap has narrowed significantly."
Negotiations on a new climate treaty began in earnest two years ago with the aim of crafting a successor to the 1997 Kyoto Protocol, which bound industrial countries to cut emissions of carbon dioxide and other Earth-warming gases from 1990 levels, but which made no obligations on countries like India and China. That omission caused much resentment and prompted the United States to reject Kyoto.
Months of deadlock were broken in the last few weeks when China and India announced voluntary targets for lowering the greenhouse gas component of economic growth. Emissions would continue to climb, but at a lower rate. They said, however, they would not accept legally binding targets that could imply consequences if they fall short.
At the same time, Obama said he would commit to an emissions cut of 17 percent from 2005, even though those cuts have not yet been approved by Congress.
Rajendra Pachauri, chairman of the Nobel Prize-winning U.N. science committee on climate change, said there is room for Obama to take more action without Congress.
"There are several areas where the executive action can enhance the level of reduction of emissions that will take place," he told The Associated Press. "There is scope for going above what is going to be legislated."
Jonathan Pershing, the senior U.S. delegate at the talks, also said the U.S. can show flexibility, even if it cannot raise its emissions offer. He said the Obama administration was showing its seriousness through budget allocations and regulatory actions on big polluters.
Pershing defended the U.S. position under Obama as a radical change from the former administration under George W. Bush.
A year ago "we had a position that this issue was not essential and not critical," he said in an AP interview, calling the shift staggering. "Think about how long it takes for a major country to fundamentally change its position, and this is a miraculously short period of rapid change," he said.
Delegates from several developing countries, however, were less optimistic, and were concerned that the major powers were cutting a deal behind the scenes that could betray their interests.
Associated Press reporters Charles J. Hanley and Karl Ritter contributed to this report.
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