Are Climate Restricted Areas a Viable Interim Climate Mitigation Option over the North Atlantic?

In order to achieve global environmental goals like the 2-degree-target, as well as to reduce longer-term emission levels, mitigation measures have to be introduced, preferably as early as possible. In aviation, the implementation of the most promising mitigation strategies, e.g. climate optimized routing, is linked with several technical challenges. An early introduction of interim mitigation strategies, which bridges the time period until most auspicious approaches reach market maturity, may pave the way for a prompt reduction of aviation's induced global warming. Within this study, climate restricted airspaces (CRA) are de�ned in analogy to military exclusion zones. Climate cost functions (CCF) characterize the environmental impact caused by an aircraft emission at a certain location and time. To estimate the monthly climate sensitivity of an area, CCFs are derived with the climate-response model AirClim. Within this study, we close regions with climate sensitivities greater than a threshold value for a period of time (e.g. a month) and a�ected ight trajectories are re-routed cost optimally around them. The evaluation of the climate impact mitigation potential of climate restricted areas is performed based on optimal control techniques. Monetary costs are integrated into the cost functional of the Trajectory Optimization Module (TOM). Further, high penalties are introduced within restricted airspaces in order to ensure the avoidance of CRA. The cost-bene�t potential (climate impact mitigation vs. rise in operating costs) for this interim mitigation concept is investigated for varying threshold values for the closure of airspace and compared with climate optimized trajectories (COT) for di�erent routes and seasons of the year

Are Climate Restricted Areas a Viable Interim Climate Mitigation Option over the North Atlantic?

In order to achieve global environmental goals like the 2-degree-target, as well as to reduce longer-term emission levels, mitigation measures have to be introduced, preferably as early as possible. In aviation, the implementation of the most promising mitigation strategies, e.g. climate optimized routing, is linked with several technical challenges. An early introduction of interim mitigation strategies, which bridges the time period until most auspicious approaches reach market maturity, may pave the way for a prompt reduction of aviation's induced global warming. Within this study, climate restricted airspaces (CRA) are de�ned in analogy to military exclusion zones. Climate cost functions (CCF) characterize the environmental impact caused by an aircraft emission at a certain location and time. To estimate the monthly climate sensitivity of an area, CCFs are derived with the climate-response model AirClim. Within this study, we close regions with climate sensitivities greater than a threshold value for a period of time (e.g. a month) and a�ected ight trajectories are re-routed cost optimally around them. The evaluation of the climate impact mitigation potential of climate restricted areas is performed based on optimal control techniques. Monetary costs are integrated into the cost functional of the Trajectory Optimization Module (TOM). Further, high penalties are introduced within restricted airspaces in order to ensure the avoidance of CRA. The cost-bene�t potential (climate impact mitigation vs. rise in operating costs) for this interim mitigation concept is investigated for varying threshold values for the closure of airspace and compared with climate optimized trajectories (COT) for di�erent routes and seasons of the year

Influence of weather situation on non-CO₂ aviation climate effects: the REACT4C climate change functions

Emissions of aviation include CO2, H2O, NOx, sulfur oxides, and soot. Many studies have investigated the annual mean climate impact of aviation emissions. While CO2 has a long atmospheric residence time and is almost uniformly distributed in the atmosphere, non-CO2 gases and particles and their products have short atmospheric residence times and are heterogeneously distributed. The climate impact of non-CO2 aviation emissions is known to vary with different meteorological background situations. The aim of this study is to systematically investigate the influence of characteristic weather situations on aviation climate effects over the North Atlantic region, to identify the most sensitive areas, and to potentially detect systematic weather-related similarities. If aircraft were re-routed to avoid climate-sensitive regions, the overall aviation climate impact might be reduced. Hence, the sensitivity of the atmosphere to local emissions provides a basis for the assessment of weather-related, climate-optimized flight trajectory planning. To determine the climate change contribution of an individual emission as a function of location, time, and weather situation, the radiative impact of local emissions of NOx and H2O to changes in O3, CH4, H2O and contrail cirrus was computed by means of the ECHAM5/MESSy Atmospheric Chemistry model. From this, 4-dimensional climate change functions (CCFs) were derived. Typical weather situations in the North Atlantic region were considered for winter and summer. Weather-related differences in O3, CH4, H2O, and contrail cirrus CCFs were investigated. The following characteristics were identified: enhanced climate impact of contrail cirrus was detected for emissions in areas with large-scale lifting, whereas low climate impact of contrail cirrus was found in the area of the jet stream. Northwards of 60∘ N, contrails usually cause climate warming in winter, independent of the weather situation. NOx emissions cause a high positive climate impact if released in the area of the jet stream or in high-pressure ridges, which induces a south- and downward transport of the emitted species, whereas NOx emissions at, or transported towards, high latitudes cause low or even negative climate impact. Independent of the weather situation, total NOx effects show a minimum at ∼250 hPa, increasing towards higher and lower altitudes, with generally higher positive impact in summer than in winter. H2O emissions induce a high climate impact when released in regions with lower tropopause height, whereas low climate impact occurs for emissions in areas with higher tropopause height. H2O CCFs generally increase with height and are larger in winter than in summer. The CCFs of all individual species can be combined, facilitating the assessment of total climate impact of aircraft trajectories considering CO2 and spatially and temporally varying non-CO2 effects. Furthermore, they allow for the optimization of aircraft trajectories with reduced overall climate impact. This also facilitates a fair evaluation of trade-offs between individual species. In most regions, NOx and contrail cirrus dominate the sensitivity to local aviation emissions. The findings of this study recommend considering weather-related differences for flight trajectory optimization in favour of reducing total climate impact

Influence of the actual weather situation on non-CO2 aviation climate effects: The REACT4C Climate Change Functions

The influence of different weather situations on non-CO2 aviation climate impact is investigated. The aim is to identify systematic weather related sensitivities. If aircraft trajectories avoid the most sensitive areas, the overall climate impact might be reduced. An enhanced significance of the position of emission release is identified in relation to high pressure systems, in relation to the jet stream, in relation to polar night, and in relation to the altitude of the tropopause. The results of this study represent a comprehensive dataset for studies aiming at weather dependent flight trajectory optimization reducing total climate impact

Mitigating the Climate Impact from Aviation: Achievements and Results of the DLR WeCare Project

The WeCare project (Utilizing Weather information for Climate efficient and eco efficient future aviation), an internal project of the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt, DLR), aimed at finding solutions for reducing the climate impact of aviation based on an improved understanding of the atmospheric impact from aviation by making use of measurements and modeling approaches. WeCare made some important contributions to advance the scientific understanding in the area of atmospheric and air transportation research. We characterize contrail properties, show that the aircraft type significantly influences these properties, and how contrail-cirrus interacts with natural cirrus. Aviation NOx emissions lead to ozone formation and we show that the strength of the ozone enhancement varies, depending on where within a weather pattern NOx is emitted. These results, in combination with results on the effects of aerosol emissions on low cloud properties, give a revised view on the total radiative forcing of aviation. The assessment of a fleet of strut-braced wing aircraft with an open rotor is investigated and reveals the potential to significantly reduce the climate impact. Intermediate stop operations have the potential to significantly reduce fuel consumption. However, we find that, if only optimized for fuel use, they will have an increased climate impact, since non-CO2 effects compensate the reduced warming from CO2 savings. Avoiding climate sensitive regions has a large potential in reducing climate impact at relatively low costs. Taking advantage of a full 3D optimization has a much better eco-efficiency than lateral re-routings, only. The implementation of such operational measures requires many more considerations. Non-CO2 aviation effects are not considered in international agreements. We showed that climate-optimal routing could be achieved, if market-based measures were in place, which include these non-CO2 effects. An alternative measure to foster climate-optimal routing is the closing of air spaces, which are very climate-sensitive. Although less effective than an unconstrained optimization with respect to climate, it still has a significant potential to reduce the climate impact of aviation. By combining atmospheric and air Transportation research, we assess climate mitigation measures, aiming at providing information to aviation stakeholders and policy-makers to make aviation more climate compatible

Mitigating the Climate Impact from Aviation: Achievements and Results of the DLR WeCare Project

The WeCare project (Utilizing Weather information for Climate efficient and eco efficient future aviation), an internal project of the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt, DLR), aimed at finding solutions for reducing the climate impact of aviation based on an improved understanding of the atmospheric impact from aviation by making use of measurements and modeling approaches. WeCare made some important contributions to advance the scientific understanding in the area of atmospheric and air transportation research. We characterize contrail properties, show that the aircraft type significantly influences these properties, and how contrail-cirrus interacts with natural cirrus. Aviation NOx emissions lead to ozone formation and we show that the strength of the ozone enhancement varies, depending on where within a weather pattern NOx is emitted. These results, in combination with results on the effects of aerosol emissions on low cloud properties, give a revised view on the total radiative forcing of aviation. The assessment of a fleet of strut-braced wing aircraft with an open rotor is investigated and reveals the potential to significantly reduce the climate impact. Intermediate stop operations have the potential to significantly reduce fuel consumption. However, we find that, if only optimized for fuel use, they will have an increased climate impact, since non-CO2 effects compensate the reduced warming from CO2 savings. Avoiding climate sensitive regions has a large potential in reducing climate impact at relatively low costs. Taking advantage of a full 3D optimization has a much better eco-efficiency than lateral re-routings, only. The implementation of such operational measures requires many more considerations. Non-CO2 aviation effects are not considered in international agreements. We showed that climate-optimal routing could be achieved, if market-based measures were in place, which include these non-CO2 effects. An alternative measure to foster climate-optimal routing is the closing of air spaces, which are very climate-sensitive. Although less effective than an unconstrained optimization with respect to climate, it still has a significant potential to reduce the climate impact of aviation. By combining atmospheric and air transportation research, we assess climate mitigation measures, aiming at providing information to aviation stakeholders and policy-makers to make aviation more climate compatible.Aircraft Noise and Climate Effect