Aircraft emit staggering amounts of CO2, the most prevalent manmade greenhouse gas. In fact, they currently account for 11 percent of CO2 emissions from U.S. transportation sources and 3 percent of the United States’ total CO2 emissions. All told, the United States is responsible for nearly half of worldwide CO2 emissions from aircraft.
In addition to CO2, aircraft emit nitrogen oxides, known as NOx, which contribute to the formation of ozone, another greenhouse gas. Emissions of NOx at high altitudes result in greater concentrations of ozone than ground-level emissions. Aircraft also emit water vapor at high altitudes, creating condensation trails or “contrails,” visible cloud lines that form in cold, humid atmospheres and contribute to the warming impacts of aircraft emissions. The persistent formation of contrails is associated with increased cirrus cloud cover, which also warms the Earth’s surface. All told, aircraft’s high-altitude emissions have a greater global warming impact than they would if the emissions were released at ground level.
Alarmingly, aircraft emissions are expected to more than triple by mid-century. But the Center is working to make sure that prediction doesn’t come true: In December 2007, we joined with states, regional governments and other conservation groups to petition the U.S. Environmental Protection Agency to address the effects of aircraft pollution under the Clean Air Act. The agency continued to drag its feet on the issue, so in June 2010 the Center and allies sued the agency for its failure to address global warming pollution from aircraft, ships and nonroad vehicles. The next year, a court ruled the EPA must formally determine whether greenhouse gas pollution from aircraft endangers human health and welfare.
It’s crucial that the Environmental Protection Agency and air industry do their part to fight global warming. This means adopting operational measures to minimize fuel use and reduce emissions from aircraft; requiring the use of lighter, more efficient airplanes; and producing and using cleaner jet fuels.
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