Climate effect of ozone changes caused by present and future air traffic

 The potential of aircraft-induced ozone changes to force a substantial climate impact is investigated by means of simulations with an atmospheric general circulation model, coupled to a mixed layer ocean model. We present results from several numerical experiments that are based on ozone change patterns for 1992 aviation and on a future scenario for the year 2015. In both cases, the climate signal is statistically significant. The strength of the ozone impact is of comparable magnitude to that arising from aircraft CO2 emissions, thus meaning a non-negligible contribution to the total climate effect of aviation emissions. There are indications of a characteristic signature of the aircraft ozone related temperature response pattern, distinctly different from that associated with the increase of well-mixed greenhouse gases. Likewise, the climate sensitivity to non-uniform ozone changes including a strong concentration perturbation at the tropopause may be higher than the climate sensitivity to uniform changes of a greenhouse gas. In a hierarchy of experiments, for which the spatial structure of an aircraft-related ozone perturbation was left fixed, while the amplitude of the perturbation was artificially increased, the climate signal depends in a non-linear way on the radiative forcing.