FILE - This March 9, 2010 file photo shows a tanker truck 

FILE - This March 9, 2010 file photo shows a tanker truck passing the Chevron oil refinery in Richmond, Calif. Slowing the buildup of greenhouse gases responsible for warming the planet is one of the biggest challenges the U.S. _ and President Barack Obama _ faces. The impacts of rising global temperatures are widespread and costly: more severe storms, rising seas, species extinctions, and changes in weather patterns that will alter food production and the spread of disease. (AP Photo/Paul Sakuma, File)
Associated Press
FILE - This March 9, 2010 file photo shows a tanker truck passing the Chevron oil refinery in Richmond, Calif. Slowing the buildup of greenhouse gases responsible for warming the planet is one of the biggest challenges the U.S. _ and President Barack Obama _ faces. The impacts of rising global temperatures are widespread and costly: more severe storms, rising seas, species extinctions, and changes in weather patterns that will alter food production and the spread of disease. (AP Photo/Paul Sakuma, File)
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