Aviation, Marine, Rail - Aviation
In recent years, an awareness of the environmental impacts of air travel has been increasing. Although much of the focus has been on noise, aircraft emissions have become a topic of concern, as well. Aircraft produce the same types of emissions as cars and trucks. In particular, aircraft jet engines produce carbon dioxide (CO2), water vapor (H2O), nitrogen oxides (NOx), carbon monoxide (CO), oxides of sulfur (SOx), unburned or partially combusted hydrocarbons (also known as volatile organic compounds, or VOCs), particulates, and other trace compounds. Aircraft engine emissions are roughly composed of about 70 percent CO2, a little less than 30 percent H2O, and less than 1 percent each of NOx, CO, SOx, VOC, particulates, and other trace components.
Relationship to Climate Change
As with surface vehicles, aircraft produce carbon dioxide through combustion of petroleum-based fuel. Aircraft can have complex effects on climate through contrail formation and by emitting water vapor into the dry stratosphere. Aviation accounts for about 10 percent of greenhouse gas emissions from transportation in the U.S., or about 2.7 percent of total national greenhouse gas emissions. Air travel has grown significantly in the past decade, and is expected to continue to do so in the coming years.
However, there are many strategies targeted to improving the efficiency of our nation's air travel system that also have ancillary benefits related to the reduction of greenhouse gas emissions. Aircraft fuel efficiency has historically increased at about 1 percent per year, and research continues to explore engine efficiency, airframe aerodynamics, and the use of lighter materials. Changes in a variety of other factors such as operating procedures, aircraft routing, and load factors can also have significant impacts on greenhouse gas emissions per passenger mile.
Government Accountibility Office. GAO-09-554. 2009.
Intergovernmental Panel on Climate Change
This IPCC Special Report assesses the effects of aircraft on climate and atmospheric ozone.
U.S. Department of Transportation, Center for Climate Change
This 2006 workshop reviewed the current state of knowledge, identified gaps in scientific knowledge and prioritized research, recommending leveraging current and future research, and development of impact metrics for evaluating impacts and trade-off options. A recommendation was also made regarding the coordination and expansion of existing and planned climate research programs focusing on aviation.