FILE - In this Wednesday, Aug. 8, 2012 file photo, a dry corn field receives some rain from a passing thunderstorm near Blair, Neb. Nearly 4 out of 5 Americans now think temperatures are rising and that global warming will be a serious problem for the United States if nothing is done about it, a new Associated Press-GfK poll finds. Belief and worry about climate change are inching up among Americans in general, but concern is growing faster among people who don't often trust scientists on the environment. In follow-up interviews, some of those doubters said they believe their own eyes as they've watched thermometers rise, New York City subway tunnels flood, polar ice melt and Midwestern farm fields dry up. (AP Photo/Nati Harnik, File)
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