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When it is burned to produce electricity (petroleum, natural gas, coal) emits the most carbon dioxide. This fossil fuel accounted for ( 1/3, 1/2, 3/4 ) of the electricity generated in the United States and emitted 68 percent of the carbon dioxide produced by generating electricity.

When it is burned to produce electricity,  coal emits the most carbon dioxide. This fossil fuel accounted for 1/3 of the electricity generated in the United States and emitted 68 percent of the carbon dioxide produced by generating electricity.

Gases like carbon dioxide increase the temperature and cause global warming. Carbon dioxide makes the vast majority of greenhouse gas emissions from the electricity sector.