Country representatives listen to opening remarks at the start of the United Nations' Conference of the Parties on Climate Change in Lima, Peru. Cris Bouroncle/AFP/Getty Images hide caption

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U.S. President Barack Obama, right, smiles after a group of children waved flags and flowers to cheer him during a welcome ceremony Wednesday with Chinese President Xi Jinping at the Great Hall of the People in Beijing. In a surprise agreement late Tuesday, China agreed to a first-ever target for capping its carbon emissions, while the United States pledge to cut faster than previously planned. Andy Wong/AP hide caption

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An oil refinery is pictured in the southern Sydney suburb of Kurnell earlier this week. Australia's Senate voted on Thursday to scrap the country's carbon tax and plans for emissions trading — a major victory for conservative Prime Minister Tony Abbott. Jason Reed/Reuters/Landov hide caption

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The EPA is proposing rules that would govern carbon dioxide gas emissions by U.S. power plants. Here, coal is transported via conveyor belt to the coal-fired Jim Bridger Power Plant outside Point of the Rocks, Wyo., in March. Jim Urquhart/Reuters /Landov hide caption

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The Capitol dome is seen behind the Capitol Power Plant, which provides power to buildings in the Capitol complex in Washington, D.C. Carolyn Kaster/AP hide caption

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Ken Caldeira of the Carnegie Institution for Science takes a water sample during his experiment out on part of the Great Barrier Reef. The water is slightly pink because his team is using a dye to trace an acid-neutralizing chemical as it flows across the reef. Richard Harris/NPR hide caption

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Climate activists at a rally in Doha on December 1, 2012. Karim Jaafar/AFP/Getty Images hide caption

itoggle caption Karim Jaafar/AFP/Getty Images