There is a direct correlation to carbon dioxide emissions and global warming. Since the industrial revolution, the levels of carbon dioxide have been steadily rising. This is due to the combustion of fossil fuels. Coal was the primary fossil fuel during the industrial revolution and then, oil and gas became important fuel sources to power modern transportation vehicles. Coal is still important in generating electricity. Fossil fuels are hydrocarbon fuels. When burned, carbon dioxide is added to the atmosphere.This gas can act like a greenhouse. The sun's rays pass through the atmosphere and some is converted to heat energy or infrared energy. Normally, this heat would radiate away from Earth's surface. However, due to the carbon dioxide in the atmosphere, it becomes trapped near Earth's surface and causes the temperatures to rise. This is the greenhouse effect.