BONN, Germany (AP) âÄî Once booed at international climate talks, the United States won sustained applause Sunday when President Barack Obama’s envoy pledged to “make up for lost time” in reaching a global agreement on climate change. Todd Stern also praised efforts by countries like China to reign in their carbon emissions, but said global warming “requires a global response” and that rapidly developing economies like China “must join together” with the industrial world to solve the problem. The debut of Obama’s climate change team was widely anticipated after eight years of obdurate participation in U.N. climate talks by the previous Bush administration. “We are very glad to be back. We want to make up for lost time, and we are seized with the urgency of the task before us,” Stern said to loud applause from the 2,600 delegates to the U.N. negotiations. They clapped again when Stern said the U.S. recognized “our unique responsibility … as the largest historic emitter of greenhouse gases,” which has created a problem threatening the entire world. The two-week meeting by 175 countries that began Sunday was the latest stage of talks aimed at forging a climate change agreement to replace the 1997 Kyoto Protocol on emissions targets for rich countries, which expires in 2012. The United States was instrumental in negotiating Kyoto, but failed to win support at home. When George W. Bush took office, he renounced it, calling Kyoto a flawed agreement that would harm the U.S. economy and unfair because it demanded nothing from countries like China or India. Stern said his team did not want a repeat of the Kyoto debacle. The latest agreement is due to be finalized in December in Copenhagen, Denmark. “Ultimately, this is a political process,” he said. “The way forward is steered by science and pragmatism.” Stern said no one on his team doubted that climate change is real. “The science is clear, the threat is real, the facts on the ground are outstripping the worst-case scenarios. The cost of inaction or inadequate action are unacceptable,” he said âÄî a total change of tone from his predecessors. Scientists warned recently that climate change is happening more rapidly that previously calculated and said the Earth could be in danger of major climatic changes that would trigger widespread social disruption. U.N. scientists say rising sea levels caused by global warming threatens to swamp coastlines and entire island states, and predicted increasing drought for arid countries, especially in Africa. Obama has set aside $80 billion in his economic stimulus package for green energy, promised $150 billion for research over 10 years, and was tightening regulations on auto emissions, Stern said. “America itself cannot provide the solution, but there is no solution without America,” he said. “It sent chills up my spine seeing the U.S. applauded,” Keya Chatterjee of the Worldwide Fund for Nature said after Stern’s speech. It was only 15 months ago at Bali, Indonesia, that U.S. negotiators were booed when they threatened to veto an accord laying down a two-year negotiating process to replace Kyoto. They backed off when the delegate from Papua New Guinea, Kevin Conrad, told them if “you are not willing to lead … please get out of the way.” Stern urged delegates Sunday to adopt a long-range vision for reducing climate change, rather than to focus on “a series of short-term, stopgap measures,” and repeated Obama’s determination to cut emissions by 80 percent by mid-century. His speech was meant to shift the debate from persistent demands by developing countries for industrial nations to reduce emissions by 25-40 percent below 1990 levels by 2020. Stern has said previously that goal was unattainable for the U.S. Speaking earlier to reporters, Stern defended the U.S. administration’s goal of reducing U.S. carbon emissions by roughly 16 percent over the next dozen years from current levels. “We don’t think (the target) is low at all,” he said, adding it was “consistent with what other countries are willing to do.” Others disagreed. “The target that the United States has put forward is not going to be sufficient,” said Chatterjee. Jake Schmidt of the Nature Resources Defense Council said the Obama administration was talking behind the scenes about setting an annual emissions reduction target leading up to 2050. “It’s hard to turn a big ship around, but it would show we are serious about our commitments to cut emissions from the medium to the long term,” Schmidt said. With time running out before the pact is due to be completed in December, delegates are trying to narrow vast differences over how best to fight climate change. Issues include how much countries need to reduce emissions, how to raise the tens of billions of dollars needed annually to fight global warming and how to transfer money and technology to poor countries who are most vulnerable to increasingly fierce storms, droughts and failing crops. Stern said the U.S. position will be guided by whatever deal Obama can strike with Congress. “I do not think that it is realistic to believe that we will then be able to go into an international setting and get a higher number than that,” he said.