Vehicular Emissions That Contribute to Global Warming

Carbon monoxide, ozone, particulate matter, and the other forms of pollution listed above can cause smog and other air quality concerns, but there are vehicular emissions that contribute to a completely different pollution issue: global warming.

During the morning rush hour, the Miguel Hidalgo area of Mexico City is clogged with traffic and smog. (©Stephanie Maze/Corbis. Reproduced by permission.)

Morning rush hour traffic waiting to pay the toll to cross the Oakland Bay Bridge in August 1989. (©James A. Sugar/Corbis. Reproduced by permission.)

The gases that contribute to global warming are related to the chemical composition of the Earth's atmosphere. Some of the gases in the atmosphere function like the panes of a greenhouse. They let some radiation (heat) in from the sun but do not let it all back out, thereby helping to keep the Earth warm. The past century has seen a dramatic increase in the atmospheric concentration of heat-trapping gasses, due to human activity. If this trend continues, scientists project that the earth's average surface temperature will increase between 2.5°F and 10.4°F by the year 2100.

One of these important heat-trapping gasses is carbon dioxide (CO2). Motor vehicles are responsible for almost one-quarter of annual U.S. emissions of CO2. The U.S. transportation sector emits more CO2 than all but three other countries' emissions from all sources combined.

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