At a Crossroads in the Sky: Tackling Aerosols, Contrails, and a Sustainable Future for Aviation
RICHARD MOORE, NASA
Abstract Number: 29
Working Group: Plenary Lecture Invited by Conference Chair
Abstract
If the global aviation sector were a country, it would be one of the top ten carbon dioxide emitters, and yet, models tell us that aircraft CO2 is not even the biggest aviation climate impact today. Line-shaped contrails and the cirrus clouds that result from them are thought to have a greater radiative forcing than all of the accumulated aviation CO2 emitted since the Wright Brothers’ first flights. Despite this importance, the model representation of contrail-cirrus remains highly uncertain, which is due in part to a lack of observational data at cruise altitudes. In addition, aircraft emissions impact local air quality on the ground near airports. Sustainable aviation fuels (SAF) and advanced lean-burn aircraft engines are promising solutions toward reducing aircraft engine particle emissions that drive these air quality and climate effects. Hydrogen-fueled aircraft also seem, at first glance, to be an attractive option for eliminating the soot particles seeding contrails; although, new particle formation and gas-to-particle conversion of semi-volatile lubrication oil emissions downstream of the gas turbines may compensate for the hard won gains in removing the soot coming from the combustor. Last, there are open questions about how aviation aerosols may interact with natural cirrus clouds and also emerging regulatory interest in optimizing flight trajectories to avoid the ice supersaturated regions of the atmosphere where contrail cirrus form and persist. Developing a coherent engineering and/or policy response requires a clear understanding of these aerosol science and aerosol-cloud interactions processes. This presentation highlights the current state of the science and key research gaps that need to be addressed to ensure a sustainable and robust future for aviation as a critical economic and societal benefit.