This year America's weather has been hotter and more extreme than ever before, records show. Yet the presidential candidates aren't talking about it.
In the U.S. July was the hottest month ever recorded, and this year is on track to be the warmest. Scientists say that's both from natural drought and man-made global warming. Each decade since the 1970s has been nearly one-third of a degree warmer than the previous one.
Sea levels are rising while glaciers and summer Arctic sea ice are shrinking. Plants are blooming earlier. Some species could die because of global warming.
Obama proposed a bill to cap power plant carbon dioxide emissions, but it died in Congress. Still, he's doubling auto mileage standards and put billions into cleaner energy. Romney now questions the science of man-made global warming and says some actions to curb emissions could hurt an already struggling economy.
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