Climate efforts gaining ground

? 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.

“Time is up,” de Boer said. “Over the next two weeks governments have to deliver.”

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.

Nations also must need to commit to larger emission reductions, de Boer said.

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, after phone consultations with other heads of state, was taken as a signal that an agreement was getting closer. He originally planned to make only an hourslong 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 ever held on climate.

“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.”