Despite the significant progress that has been made in reducing the specific emissions of aircraft, the absolute emissions have been increasing rapidly during the recent decades and are projected to continue to grow. Aviation CO2 emissions in the EU nearly doubled over the period 1990 to 2005. Furthermore, aviation substantially impacts upon climate from non-CO2 effects such as ozone formation and methane destruction from aviation’s NOx emissions, the formation of contrails and contrail cirrus, the emission of H2O at high altitudes, emission of aerosols (e.g. soot) and aerosol precursors (e.g. SOx), which are directly radiatively active and which modify cloudiness and cloud micro- physical and radiative properties.

The ultimate goal of ECATS is to contribute to solutions for a more environmentally sustainable aviation system. There are two principle pathways to that goal, namely (1) reducing the emissions and (2) reducing the climatic effects of the emissions. The first pathway proceeds mainly via novel technological solutions which are investigated in ECATS as one thematic area (TA1).

The second pathway, reducing the climatic effects of emissions requires adapted flight operations that take into account the state of the atmosphere at the time and location of the specific emission.

ECATS thematic area 3 (TA3) conducts research in order to increase the understanding of the effects of emissions in specific regions of the atmosphere. This research helps to reduce current uncertainties and helps to provide guidance to stakeholders and policy makers. In cases where uncertainties cannot be reduced substantially, for whatever reason, we explore the range of possibilities in order to allow robust decisions to be taken, i.e. decisions that work in almost all conceivable circumstances.

ECATS TA3 helps to develop operational mitigation strategies with respect to aviation’s climate impact. One particular aspect is avoiding contrails that warm climate. Such contrails form in so-called ice supersaturated regions in the upper troposphere. Therefore we investigate properties of these regions and help aviation weather forecast to predict them in order to allow a flight routing that is able to take contrail effects into account.

Another aspect is to investigate aviation global warming potential (GWP) due to NO_x emissions. Chemical impact of NO_x is highly non-linear. Short term warming effect due to ozone formation is compensated by a long-term indirect methane lifetime effect. The residium of both effects depends also on assumed time horizon for evaluating climate impact.