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Transportation and Climate Change Clearinghouse

The Transportation and Climate Change Clearinghouse is designed as a one-stop source of information on transportation and climate change issues. It includes information on greenhouse gas (GHG) inventories, analytic methods and tools, GHG reduction strategies, potential impacts of climate change on transportation infrastructure, and approaches for integrating climate change considerations into transportation decision making.

Transportation and Greenhouse Gas Emissions

Virtually all human activities have an impact on our environment, and transportation is no exception. While transportation is crucial to our economy and our personal lives, as a sector it is also a significant source of greenhouse gas (GHG) emissions.

Based on current GHG emission reporting guidelines, the transportation sector directly accounted for about 28 percent of total U.S. GHG emissions in 2006, making it the second largest source of GHG emissions, behind only electricity generation (34 percent). Nearly 97 percent of transportation GHG emissions came through direct combustion of fossil fuels, with the remainder due to carbon dioxide (CO2) from electricity (for rail) and Hydrofluorocarbons (HFCs) emitted from vehicle air conditioners and refrigerated transport. Transportation is the largest end-use sector emitting CO2, the most prevalent greenhouse gas. Estimates of GHG emissions do not include additional "lifecycle" emissions related to transportation, such as the extraction and refining of fuel and the manufacture of vehicles, which are also a significant source of domestic and international GHG emissions.

Pie chart of U.S. greenhouse gas emissions by economic sector, 2012

Since 1990, transportation has been one of the fastest-growing sources of U.S. GHGs. In fact, the rise in transportation emissions represents 48 percent of the increase in total U.S. GHGs since 1990.

U.S. greenhouse gas emissions by economic sector from 1990 to 2013

The largest sources of transportation GHGs are light vehicles (passenger cars, sport utility vehicles, pickup trucks, minivans, and motorcycles). In 2012, these vehicles accounted for about 59% of transportation GHG emissions. The next largest sources were freight trucks (22%) and commercial aircraft (8%), along with other non-road sources (10%). 

Greenhouse gas emissions by mode of transportation,  2012

It is important to note that fuel consumed in international travel by aircraft and marine sources is not counted in national greenhouse gas inventories. However, international trade has been growing rapidly, thus increasing the role of transportation as a source of global emissions.

About the Center

The Department of Transportation established the Center for Climate Change and Environmental Forecasting in 1999. The Center has become the focal point within DOT for information and technical expertise on transportation and climate change, working with its component organizations to coordinate related research, policies, and actions. The Center promotes comprehensive multimodal approaches to reduce GHG emissions and prepare for the effects of climate change on the transportation system, while advancing DOT's core goals of safety, mobility, environmental stewardship, and security.

Updated: Thursday, March 9, 2017
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