Trade-off between Contrail Reduction and Emissions under Future US Air Traffic Scenarios

Abstract

This paper examines how future contrail reduction strategies in the United States, limited by airspace capacity constraints, may impact future CO 2 emissions and average global temperature. Future 2025 air traffic in the National Airspace System is simulated for a series of assumed air traffic growth rates ranging from 1.15 times to 2.0 times 2010 traffic levels. Contrail reduction strategies using altitude changes are then simulated, trading off contrail reduction with increased CO 2 emissions. Altitude changes are limited, however, by airspace sector capacities, according to assumed sector capacity growth scenarios. Future fleet turnover is simulated in order to capture potential changes in CO 2 emissions resulting from the introduction of new technology, based on assumptions about future technology and fleet entry. Sample future sector counts are shown for four sectors with high traffic in Kansas City Air Route Traffic Control Center. The trade-off between system-wide contrail reduction and extra CO 2 emissions, and the resulting impact on absolute global temperature potential is also shown. The results suggest that contrail reduction through altitude changes is likely to have climate benefits under future traffic levels, particularly when aircraft can change altitude by up to 4,000 ft. The results also suggest that, while airspace capacity constraints may reduce the degree to which contrails can be avoided, they are unlikely to significantly reduce the climate benefits of contrail avoidance. These results assume, however, that airspace capacity would increase if the higher forecasts of traffic growth (e.g., 1.5 times or 2 times 2010 traffic levels) materialize. The results also suggest that while different weather days and different assumptions about the climate impact of contrails lead to significant changes in the results, the general trends remain unchanged, and the ratio of contrail reduction to extra CO 2 emissions at which climate impact is minimized remains approximately constant.