UNITED NATIONS — Although some 100 world leaders met Tuesday for a U.N. climate summit, most of the attention was on just two — President Barack Obama and China's Hu Jintao. Both vowed to take the threat of rising seas, drought and deforestation seriously, but only one had some momentum behind him and it wasn't Obama.
Following criticism that the United States was losing ground on climate policy, Obama told his peers that while the "journey is hard" his administration would "meet our responsibility to future generations."
Obama acknowledged that pursuing costly emissions reductions is difficult at a time when the world is trying to recover from a recession, but said it has to be done.
"We don't have much time left to make it," Obama told the highest-level conference yet on climate change. "We understand the gravity of the climate threat. We are determined to act. And we will meet our responsibility to future generations."
Obama said his administration has made the "largest-ever" American investment in renewable energy: doubling the generating capacity from wind and other renewable resources in three years, launching offshore wind energy projects and spending billions to capture carbon pollution from coal plants.
Activists on Tuesday criticized Obama's speech for lacking specifics. "While other countries announced specific targets and timetables, including China, Japan and the Maldives, President Obama did not address these critical elements," said Keya Chatterjee, head of the World Wildlife Fund's climate program.
The United States hasn't passed any mandatory curbs on greenhouse gases, and the U.N. climate chief on Monday said China was leaping ahead of the U.S. in terms of climate leadership.
"China and India have announced very ambitious national climate change plans," Yvo de Boer said. "In the case of China, so ambitious that it could well become the front-runner in the fight to address climate change," de Boer said. "The big question mark is the U.S."
'China fully appreciates' urgency
In his speech, China's president vowed China would plant enough forest to cover an area the size of Norway and generate 15 percent of its energy needs from renewable sources within a decade.
Slideshow: Climate conditions "At stake in the fight against climate change are the common interests of the entire world," Hu said. "Out of a sense of responsibility to its own people and people across the world, China fully appreciates the importance and urgency of addressing climate change."
While Hu's comments were well received, he did not budge from China's stance that it and other developing economies should not have to agree to mandatory cuts in greenhouse gases. Developing nations "should not ... be asked to take on obligations that go beyond their development stage," Hu said.
Beijing wants to link emissions to growth in gross domestic product, meaning it still may increase emissions even as it takes fundamental steps to curb them in the long run.
China and the U.S. each account for about 20 percent of all the world's greenhouse gas pollution created when coal, natural gas or oil are burned. The European Union is next, generating 14 percent, followed by Russia and India, which each account for 5 percent.
Not much time before treaty summit
Obama sought to show U.S. resolve ahead of crucial talks in Copenhagen in December, when nations will try to reach a new global treaty to address climate change. He spoke at the start of a busy day of diplomacy ahead of the main United Nations General Assembly meetings.
U.N. Secretary-General Ban Ki-moon opened the gathering with an appeal to leaders to set aside national interests and think about the future of the globe — and a rebuke for their foot-dragging thus far.
"The climate negotiations are proceeding at glacial speed. The world's glaciers are now melting faster than human progress to protect them — and us," the U.N. chief said.
With a mere 76 days to go before the pivotal conference, it appeared an interim agreement might be the most that could be expected in December, leaving difficult details for later talks.
The U.S. House of Representatives passed a climate bill this summer that would set the first mandatory limits on greenhouse gases. But action in the Senate has been delayed as lawmakers wrestle with overhauling the health care system.
Obama has announced a target of returning to 1990 levels of greenhouse emissions by 2020.
But with Congress moving slowly on a measure to curb emissions, the United States could soon find itself with little influence when 120 countries convene in Copenhagen.
Tuesday's U.N. summit and the G-20 summit in Pittsburgh at the end of this week are intended to add pressure on the United States and other rich nations to commit to cuts and provide the billions of dollars needed to help developing nations stop cutting down their forests or burning coal.
The United States, under former President George W. Bush's administration, long cited inaction by China and India as the reason for rejecting mandatory cuts in greenhouse gases.
Bush rejected the 1997 Kyoto Protocol for cutting global emissions of warming gases, which expires at the end of 2012, based on its impact on the U.S. economy and exclusion of major developing nations like China and India, both major polluters.
But neither China nor India say they will agree to binding greenhouse-gas cuts like those envisioned in a new climate pact to start in 2013. They question why they should, when not even the U.S. will agree to join rich nations in scaling back their pollution.
"The crisis today on climate change is the inability of the United States to put on the table credible emissions reduction targets for 2020," said Jairam Ramesh, India's environment minister.
The European Union is urging other rich countries to match its pledge to cut emissions by 20 percent from 1990 levels by 2020, and has said it would cut up to 30 percent if other rich countries follow suit.
Japan's incoming prime minister, whose nation generates more than 4 percent of the world's greenhouse gases, has announced a new goal of a 25 percent cut in greenhouse gas emissions from 1990 levels by 2020.
The Associated Press contributed to this report.