The GAO found that, in the United States, aviation emissions accounted for about three percent of the greenhouse gases and other emissions that contribute to the global warming phenomenon. While this percentage is small in relative terms -- other transportation sources contribute 23 percent, and other industrial emissions account for 41 percent -- aviation emissions are potentially significant for a number of reasons:
Jet aircraft emissions are deposited directly into the upper atmosphere and some of them have a greater warming effect than gases emitted closer to the surface, such as automobile exhaust.
The primary gas emitted by jet aircraft engines is carbon dioxide, which can survive in the atmosphere up to 100 years.
Carbon dioxide, combined with other exhaust gases and particulates emitted from jet engines, could have two to four times as great an impact on the atmosphere as carbon dioxide emissions alone.
The growing demand for jet air service is likely to generate more emissions that cannot be offset by reductions achieved through technological improvements alone.
The report recommended further research into the impact of jet exhaust on the global atmosphere to help guide the development of new aircraft engine technology. It also called upon governments to reduce emissions through improved air traffic control and regulatory and economic incentives.
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