When it is burned to produce electricity, <u><em>coal</em></u> emits the most carbon dioxide. This fossil fuel accounted for <u><em>1/3</em></u> 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 emissionsfrom the electricity sector.