Oil—when refined into gasoline and diesel fuel—powers more than 90 percent of the world's cars and trucks and provides all the energy for air travel. So CO2 emissions from oil are a big part of global climate change. Currently, petroleum emissions account for about 40 percent of total world CO2 emissions.

Driving and CO2

The average car, driven 12,000 miles a year, produces about 5.5 metric tons of CO2. The more fuel a vehicle consumes, the more CO2 it emits, so generally speaking, larger vehicles produce more CO2. Because U.S. cars are less fuel-efficient than those driven elsewhere, and because its residents drive more, U.S. gas consumption per car is two to four times that in other developed nations.