Transportation's Role in Reducing U.S. Greenhouse Gas Emissions ...

Transportation's Role in Reducing U.S. Greenhouse Gas Emissions: Volume 1
lifespan of black carbon and ozone precursors, reducing their respective
emissions would reduce warming within weeks to months. 31
Figure 2.1 U.S. Transportation Greenhouse Gas Emissions by Gas, CO2e
2006
N2O
1.5%
CH4
0.1%
HFCs
3.3%
CO2
95.1%
Source: U.S. EPA (2008). Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990 to 2006.
Transportation emissions account for 29 percent of U.S. GHG emissions, and
over 5 percent of global GHG emissions. 32 Except when noted, the estimates in
this report account for “tailpipe” emissions from burning fossil fuels to power
vehicles and not greenhouse gases emitted through other transportation lifecycle
processes, such as the manufacture of vehicles, the extraction and refining of
31Unger, N., Shindell, D.T., Wang, J.S., 2009. Climate forcing by the on-road
transportation and power generation sectors. Atmos. Environ., 43, 3077-3085.
Shindell, D., Lamarque, J.F., Unger, N., Koch, D., Faluvegi, G., Bauer, S., Teich, H.,
2008. Climate forcing and air quality change due to regional emissions reductions by
economic sector. Atmos. Chem. Phys. 8, 7101–7113.
32 The estimates presented here also include fuels sold in the U.S. to aircraft and ships
traveling overseas, also known as international bunker fuels. These estimates are also
added to the U.S. total for all sectors. See Table 2.1, U.S. EPA Inventory of U.S.
Greenhouse Gas Emissions and Sinks: 1990 to 2006.
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