Journal cover Journal topic
Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
doi:10.5194/acp-2017-218
© Author(s) 2017. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
03 Apr 2017
Review status
This discussion paper is under review for the journal Atmospheric Chemistry and Physics (ACP).
Coupled Chemistry-Climate Effects from 2050 Projected Aviation Emissions
Andrew Gettelman1, Chih-Chieh Chen1, Mark Z. Jacobson2, Mary A. Cameron2, Donald J. Wuebbles3, and Arezoo Khodayari3,a 1National Center for Atmospheric Research, Boulder, CO, USA
2Stanford University, Palo Alto, CA, USA
3University of Illinois, Urbana, IL, USA
anow at: California State University Los Angeles, CA, USA
Abstract. Analyses of the climate effects of 2050 aviation emissions have been conducted with two coupled Chemistry Climate Models (CCMs) including experiments with coupled ocean models. The baseline 2050 aviation emissions scenario projects emissions ~ 5 times those in 2006. Simulations suggest a corresponding growth in the climate impact of aviation by 2050. Positive radiative forcing from contrails reaches +80 mWm−2. Enhanced upper tropospheric and lower stratospheric ozone (O3) due to aviation nitrogen oxide (NOx) emissions causes a radiative forcing of +60 mWm−2. Changes in methane (CH4) lifetime induced by aviation are estimated to cause −25 mWm−2 of radiative forcing in 2050. Simulations indicate that moderate changes in water vapor emissions from changes in combustion efficiency will not have significant forcing. Non-linear effects due to particles (black carbon and sulfur) included in these calculations suggest an important role for black carbon (BC) in increasing contrail cirrus ice crystal number, leading to net warming. Sulfur emissions brighten clouds and provide a net cooling, but this is dependent on uncertain background sulfur levels. Thus alternative aviation fuels with reduced sulfur and BC may alter the future climate impact of aviation, but the sign is dependent on specific processes represented and the background state. Regional perturbations due to contrail and particulate emissions may result in statistically significant regional surface temperature changes in coupled model simulations in areas near or adjacent to flight corridors, but significant signals only emerge after 20–50 years of simulation. Many regions with high regional aviation forcing do not experience net surface temperature changes because of advective rather than radiative driving of temperatures. Surface temperature signals are not significant globally even in long coupled simulations. Short-lived non-uniform aviation forcing will thus affect climate differently than uniform forcing in the coupled climate system.

Citation: Gettelman, A., Chen, C.-C., Jacobson, M. Z., Cameron, M. A., Wuebbles, D. J., and Khodayari, A.: Coupled Chemistry-Climate Effects from 2050 Projected Aviation Emissions, Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2017-218, in review, 2017.
Andrew Gettelman et al.
Andrew Gettelman et al.
Andrew Gettelman et al.

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Short summary
Aviation emissions create several impacts on climate. Condensation trails (contrails) are aviation produced cirrus clouds. Aircraft also emit aerosols, including soot (black carbon) and sulfate. Analyses of the climate effects of 2050 aviation emissions have been conducted with two coupled Chemistry Climate Models (CCMs) including experiments with coupled ocean models.
Aviation emissions create several impacts on climate. Condensation trails (contrails) are...
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