From left, enginers Eric Nicosia, Amin Ahmadi and Gavin Boogs work to solve an issue with part of a wind turbine at the Gamesa Corp. factory in Langhorne, Pa., on Feb. 10.
Natural gas is much cleaner than coal. But some energy analysts say an overabundance of the fuel could depress development in even cleaner energy sources like wind and solar power. Above, a rig in Washington, Pa., drills into shale rock to extract natural gas.
Key provisions of the Kyoto Protocol expire in December of 2012, and experts say there's no real global framework in place to replace the treaty that was supposed to be the first step toward ambitious actions on climate change. Above, a coal-fired power plant in eastern China. China is now the leading carbon dioxide emitter in the world.
The U.S. is second only to China in emitting gases that cause global warming. Above, the smoke stacks at American Electric Power's Mountaineer power plant in West Virginia.
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A U.N. climate panel says that we can expect more extreme weather conditions as a result of climate change. Above, people run from a high wave on Nov. 8 in Nice, France, where heavy rain and flooding forced hundreds to evacuate.
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