In recent years, mitigation of the anthropogenic climate impact has become increasingly more important. Over the past decades, the aviation industry has grown significantly, making it a large contributor to greenhouse gases in the atmosphere. One such greenhouse gas is Ozone (O3) in the troposphere, which has a warming effect on the global climate. Aviation Nitrogen Oxides (NOx) emissions play a role in the formation and loss of O3 in the troposphere, however, the chemistry is highly non-linear which makes mitigation more complex. To gain a better understanding of the contribution of aviation to tropospheric O3, this thesis looks at how aviation’s tropospheric O3 contribution varies and how the Ozone Burden Efficiency (OBE) metric can be used to better explain these global variations. The OBE is a metric which quantifies the efficiency of the background chemistry and the global transportation phenomena to promote the net formation of O3. To conduct this research, chemistry climate simulation results of the ECHAM/MESSy Atmospheric Chemistry (EMAC) model were used for a period of 2003 to 2018.

The analysis showed that across the simulated time period aviation’s contribution to tropospheric O3 increased from about 1.6% to approximately 1.9%. Looking at the vertical spread of the aviation induced O3 showed that downwards transport of O3 drives global distributions, creating large O3 mixing ratios in the free troposphere under the flight altitudes. Furthermore, the analysis of the vertical spread showed that the percentage contribution of aviation to local O3 mixing ratios is larger at ground level than at flight altitudes, showing that aviation induced O3 also contributes to air quality.

Analysing the OBE, showed that the OBE of aviation for the whole troposphere is about 4.5 Tg (O3) · Tg−1 (NOx). Further analysis showed that the OBE in the planetary boundary layer is about 2.5 Tg (O3)· Tg−1 (NOx), whereas the OBE at flight altitudes is about 1.3 Tg (O3) · Tg−1 (NOx). The larger OBE at ground level is caused by the large scale downward transport of the formed O3 and the low amount of local NOx emissions, whereas at flight altitudes, the local NOx emissions are not as small compared to the local O3 burden. Furthermore, analysis of the OBE metric also shows that the OBE of aviation is largest in the free troposphere below the flight altitudes, where it is estimated to be around 8 Tg (O3) · Tg−1 (NOx). This result highlights the large amount of O3 which is transported downwards to lower altitudes from the flight levels. Overall, the analysis using the OBE metric shows that it is most useful for emission sectors where the emissions are dominated by NOx emissions rather than carbon species which also contribute towards the production of O3. However, this attribute of the OBE metric makes it difficult to use OBE values to compare different emissions sources.

Sustainability has become an increasingly important issue, and several different governments around the world have been working towards more environmentally friendly approaches throughout different industries. This has led to measures such as the European Green Deal, which aims to make Europe climate neutral by 2050. For the aircraft industry, however, this goal creates a so-called circular causality problem. This is because there may be limited investment in increasing production of alternative energy sources due to the limited availability of aircraft that use them. On the other hand airlines may hesitate due to the limited availability of fuel to buy such aircraft. In order to solve this problem, the carbon neutral ready aircraft has been proposed. The carbon neutral ready aircraft is designed such that it initially is powered by fossil fuels and can then be converted to be powered by a carbon neutral energy source. The carbon neutral energy source that is chosen for this aircraft design is synthetic kerosene. The carbon neutral aircraft has a high wing configuration with a high aspect ratio wing. To cope with the large span of the aircraft it was decided to give the aircraft the ability of the wing tips to be folded up. Furthermore, the wing has support struts which connect the wing to the lower part of the fuselage. The propulsion system of the aircraft has two novel features: two wing mounted ultra high bypass ratio turbofan engines and an electrically powered ducted fan, which ingests the boundary layer at the aft of the fuselage. An additional five-gear configuration was chosen for the landing gear to provide the aircraft with stable ground operations while not creating a need for a fairing which interferes with the boundary layer being ingested by the aft ducted fan. Carrying out the design of this aircraft shows that the aircraft is financially feasible and performs as well as the baseline A320 aircraft in terms of payload and range, while allowing sustainability goals such as the European Grean Deal to be met. The aircraft has a 17 % emission reduction compared to the A320neo, while still employing fossil fuel based kerosene. Furthermore, at least 90% by mass of the primary structure of the aircraft is recyclable. From the recommendations however, it is clear that a lot still needs to be done before the carbon neutral aircraft can enter into service in 2030.