UNITED NATIONS (Reuters) - China laid out a plan to curb carbon emissions by 2020 and U.S. President Barack Obama called on all nations to act now to tackle global warming, as world leaders tried to inject momentum into climate change talks.
With less than three months until a United Nation conference aimed at sealing the world's toughest pact to fight climate change, U.N. Secretary-General Ban Ki-moon called Tuesday's leaders' summit to give negotiations an extra shrove.
"While the summit is not the guarantee that we will get the global agreement, we are certainly one step closer to that global goal today," Ban said at the close of the meeting.
The one-day summit drew nearly 100 heads of state and government before official talks among 190 nations in Copenhagen in December to forge a replacement to the Kyoto Protocol, whose first phase runs out at the end of 2012.
Analysts and green groups gave cautious praise to China and Japan but said Obama's speech was long on rhetoric but short on specific pledges of U.S. action.
In his address, Chinese President Hu Jintao said China's new plan included vigorously developing renewable and nuclear energy and promised emissions would grow slower than economic growth in the future.
"We will endeavor to cut carbon dioxide emissions per unit of GDP by a notable margin by 2020 from the 2005 level," Hu said.
The pledge, which marked the first time China has said it will accept measurable curbs on its emissions, was seen as an attempt to counter critics, especially in Washington, who say Beijing is doing too little to fight climate change.
Hu did not include specific figures, however. A Chinese official said those would be ready soon. But the step comes in addition to China's current aim to cut energy consumption per unit of GDP by about 20 percent by 2010 compared with 2005 levels.
New Japanese Prime Minister Yukio Hatoyama won plaudits for pledging to offer more aid to help developing countries deal with climate change and repeated his goal of reducing Japanese greenhouse gas emissions by 25 percent from 1990 levels by 2020.
Hatoyama also proposed setting up a framework to coordinate climate change aid, but did not give details of how much cash or what kind of technological assistance Japan would provide.
Obama outlined his administration's work on climate since he took office in January and said the United States was committed to act.
But he offered no new proposals and did not urge quick U.S. Senate passage of a climate bill, which many observers see as crucial to reaching an international deal.
"Our generation's response to this challenge will be judged by history, for if we fail to meet it -- boldly, swiftly and together -- we risk consigning future generations to an irreversible catastrophe," Obama said.
"The time we have to reverse this tide is running out."
Ban wanted Tuesday's summit to give momentum to a G20 meeting this week at which finance to fight climate change will be a key focus, as well as crucial U.N. climate negotiations in Bangkok from Monday, the last major negotiating round before the December 7-18 Copenhagen climate conference.
"It is slow progress, but progress nevertheless. The standout was President Hu Jintao's announcement that China will take on a 2020 carbon intensity target," said Frank Jotzo, Deputy Director of the Australian National University's Climate Change Institute in Canberra.
"The greatest difficulty for Copenhagen right now is U.S. domestic politics. It may take until well into 2010 for the U.S. to be able to make an international commitment that is credibly backed by domestic policy," he told Reuters.
A climate change bill mandating cuts in U.S. emissions is unlikely to be passed by the U.S. Senate by December while other domestic issues, notably healthcare reform, dominate the agenda.
Talks leading to the Copenhagen negotiations in Denmark have put developed and developing countries at odds over how to distribute emissions curbs. Poorer nations are pressing richer ones to contribute hundreds of billions of dollars a year to help them cope with rising temperatures.
"It was a bit disappointing that China did not give a number for greenhouse gas intensity," said Knut Alfsen, head of research at the Center for International Climate and Energy Research in Oslo. "But this is progress. Five years ago, climate was a non-issue for China."
Environmentalists criticized Obama for not putting more specifics in his first U.N. address.
"It is really more of a step back than a step forward," said Thomas Henningsen, climate coordinator for Greenpeace International.
Additional reporting by Paul Eckert, Alister Doyle and David Fogarty; Editing Alex Richardson