Greenhouse Gas Emissions

The transportation sector’s greenhouse gas (GHG) emissions in 2002 totaled 1,861.4 teragrams of carbon dioxide equivalent (TgCO₂Eq), 27 percent of total U.S. GHG emissions.¹ Transportation emissions have grown 22 percent since 1992, while total U.S. emissions rose 14 percent [1].

Carbon dioxide (CO₂) accounted for 83 percent of U.S. GHG emissions in 2002 [1]. Nearly all (97 percent) of these emissions are generated by the combustion of fossil fuels; transportation was responsible for 1,767.5 TgCO₂Eq (31 percent) of CO₂ emissions. Transportation CO₂ emissions grew 21 percent between 1992 and 2002, an average annual change of 1.9 percent (figure 10-4). Heavy-truck emissions grew the most over the period (46 percent). Aircraft emissions rose more slowly, increasing 16 percent from 1992 to 2000, then declining 8 percent in the following two years, most likely a “9/11 effect” that reduced 1992 to 2002 growth to 6 percent.² (See box 10-B for information on the two sources of U.S. GHG data.)

Highway vehicles emitted 79 percent of all transportation CO₂ emissions in 2002 and rose at an average annual rate of 2.2 percent between 1992 and 2002. Passenger cars and light-duty vehicles, which include pickup trucks, sport utility vehicles, and vans, were responsible for 79 percent of highway emissions (figure 10-5).

Most air pollutants impact local or regional air quality. Greenhouse gases, however, have the potential to alter the earth’s climate on a regional and global scale.

Source

1. U.S. Environmental Protection Agency, Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990–2002, available at http://www.epa.gov, as of May 2004.

¹ A teragram is a trillion grams.

² The GHG data here cover domestic emissions only. Figure and table 10-4 include data on international bunker fuel emissions, which result from the combustion of fuel purchased domestically but used for international aviation and maritime transportation.