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.