1GAME/CNRM, Météo France, UMR3589, CNRS, Toulouse, France
2Centre Europeén de Recherche et de Formation Avancée en Calcul Scientifique, CERFACS/CNRS, Toulouse, France
3University of Oslo and CICERO, Oslo, Norway
4Department of Meteorology and Environment Protection, Faculty of Mathematics and Physics, Charles University, Prague, V Holešoviŭkách 2, Prague 8, 180 00, Czech Republic
Abstract. This work assesses the impact of emissions from global aviation on climate, while focus is given on the temperature response. Our work is among the first that use an Atmosphere Ocean General Circulation Model (AOGCM) online coupled with stratospheric chemistry and the chemistry of mid-troposphere relevant for aviation emissions. Compared to previous studies where either the chemical effects of aviation emissions were investigated using global chemistry transport models or the climate impact of aviation was under focus implementing prescribed perturbation fields or simplified chemistry schemes, our study uses emissions as inputs and provides the climate response as output. The model we use is the Météo-France CNRM-CM5.1 earth system model extended with the REPROBUS stratospheric scheme. The timehorizon of our interest is 1940–2100 assuming the A1B SRES scenario. We investigate the present and future impact of the most relevant aviation emissions (CO2, NOx, contrail and contrail induced cirrus – CIC) as well as the impact of the non-CO2 emissions and the "Total" aviation impact. Aviation produced aerosol is not considered in the study.
The general conclusion is that the aviation emissions result in a less pronounced climate signal than previous studies suggest. Moreover this signal is more unique at higher altitudes (above the mid-troposphere) than near the surface.
The global averaged near surface CO2 impact reaches around 0.1 °C by the end of the 21st century and can be even negative in the middle of the century. The non-CO2 impact remains positive during the whole 21st century reaching 0.2 °C in its second half. A similar warming is calculated for the CIC effect. The NOx emissions impact is almost negligible in our simulations, as the aviation induced ozone production was small in the model's chemical scheme. As a consequence the non-CO2 signal is very similar to the CIC signal. The seasonal analysis showed that the strongest warming due to aviation is modeled for the late summer and early autumn months. A much less significant warming is calculated for the winter months. In the stratosphere, significant cooling is attributed to aviation CO2 emissions which reaches −0.25 °C by the end of the 21st century. A −0.3 °C temperature decrease is modeled when considering all the aviation emissions as well, but no significant signal is coming with CIC and NOx emissions in the stratosphere.