NEW YORK AND WASHINGTON — The world's two biggest producers of greenhouse gases sought to build momentum Tuesday for stalled efforts to craft a global agreement to limit emissions, with China pledging to make sweeping changes by 2020 and President Obama exhorting world leaders to act to avert catastrophe.
Critics of the two countries, which together produce 40% of the gases that cause global warming, were cheered by the cooperative tone from Obama and Chinese President Hu Jintao at a United Nations summit in New York. But they said that much more than positive words would be necessary if negotiators are to complete an international accord by a December deadline.
In his first speech during a week of international meetings, Obama made an impassioned pitch to an international community that has grown skeptical of his ability to lead the effort to confront climate change. He acknowledged that the U.S. carries a portion of the blame for global warming, offering a stark assessment of the dangers of climate change and a resounding pledge that the United States would address it.
"We understand the gravity of the climate threat," Obama said. "We are determined to act. And we will meet our responsibility to future generations."
But he stopped short of calling for Senate passage of a bill to limit greenhouse gas emissions, the one action that would most soothe international concerns about Americans' resolve on the issue.
Though declining to commit to specific reductions, China's president spoke in more detail about his nation's plans.
In his speech at the summit, Hu said that by 2020 China would plant 154,000 square miles of forest, which scrubs the air of carbon dioxide. That is an area slightly smaller than California. He set a target of drawing 15% of China's energy from non-fossil fuels by the same year, and said China would boost its efforts to develop renewable energy technology.
The U.N. conference came at a time of rising concern about progress in the talks leading up to a summit in December in Copenhagen that is intended to cap a new global climate agreement. European officials say the negotiations are nearly at a deadlock. Obama administration officials say they think there still is cause for hope, but also are leaving open the possibility that talks will extend into next year.
