(AP) -- In the highest-level conference yet on climate change, 100 world leaders come to the United Nations on Tuesday to decide how to start an energy revolution.
While attention turns to U.S. President Barack Obama's first U.N. speech, the most substantial changes may come from what the presidents of China, India and other major economies spell out for billions of people and their households, businesses and farms in the decades ahead.
Those leaders are expected to make more ambitious commitments than the U.S. leader, whose hands are still tied by Congress.
"We are asking developing countries to do as we say, not as we did," said Ed Miliband, Britain's climate secretary, whose nation has pledged to cut carbon emissions by more than a third from 1990 levels by 2020, and said 40 percent of the UK's electricity by then would come from renewable sources.
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.
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.
Chinese President Hu Jintao is expected to lay out new plans for extending China's energy-saving programs and targets for reducing the "intensity" of its carbon pollution - carbon dioxide emission increases as related to economic growth.
China has been cutting energy intensity for the past four years and could the new carbon intensity goal in a five-year plan for development until 2015. China already has said it is seeking to use 15 percent of its energy from renewable sources by 2020.
India, too, may draw away some of the spotlight for laying out plans for the fifth-biggest contributor of global warming gases to bump up fuel efficiency, burn coal more cleanly, preserve forests and grow more organic crops.
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.
Tuesday's meeting is intended to rally momentum for crafting a new global climate pact at Copenhagen, Denmark, in December. 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 EU 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.
Obama has announced a target of returning to 1990 levels of greenhouse emissions by 2020. Todd Stern, the top U.S. climate envoy, said the Obama administration is moving "full speed ahead" toward helping craft a global climate deal.
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.
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.
China's ambition to grow quickly but cleanly soon may vault it to "front-runner" status - far ahead of the United States - in taking on global warming, the U.N. climate chief said Monday.
"China and India have announced very ambitious national climate change plans. In the case of China, so ambitious that it could well become the front-runner in the fight to address climate change," U.N. climate chief Yvo de Boer told The Associated Press. "The big question mark is the U.S."
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