Integrating climate policies into air transport operations: Challenges, Risks, and Impacts

Kurzfassung

The aviation sector’s climate impact extends beyond CO2, with non-CO2 effects such as from contrails and nitrogen oxides causing up to two third of the total climate impact. From January 1, 2025, EU regulations require aircraft operators to monitor and report CO2 equivalent emissions (CO2e) per flight. By December 2027, the EU may expand the Emissions Trading System to price non-CO2 emissions, encouraging climate-friendly flight planning and affecting ticket prices under the 'Polluter-Pays Principle.' This paper consolidates findings from the Horizon Europe project BeCoM (Better Contrails Mitigation) on the implications of non-CO₂ pricing for aviation, covering flight routing, climate impact, ticket prices, and passenger demand. Operational non-CO2 mitigation depends on weather, while ticket price increases are mainly influenced by the accounted CO₂e share and the applied carbon price. A gradual rollout of CO₂e pricing, e.g. starting with 20% of CO₂e emissions in the first year, could help to limit initial cost impacts for passengers. Dependent on the accounted CO₂e share, ticket prices of analyzed inner European flights may rise between 1.0% and 4.8%. Estimated CO₂e abatement costs range from €3 to €74 per ton (median: €14 per ton), with lower costs on days when contrail avoidance is effective. These figures remain below typical abatement costs in sectors such as wind, solar, or direct air capture. Incorporating cooling contrails into pricing could potentially offset or lower costs by providing compensation, although this approach is subject to debate and controversy due to concerns over increased risks. Further analyses assess how non-CO₂ pricing under the EU ETS might influence passenger demand across three different regulatory scopes: full coverage of all flights, including those within and outside the European Economic Area (EEA); a reduced scope limited to intra-European routes; and a departure-allocation scope covering only outbound flights. Using a passenger preference model, we find that costs vary greatly depending on route and fleet, leading to distinct effects on ticket prices. This results to demand shifts to routes without pricing, shorter feeder flights or higher market prices. We also explore the mitigation potential and cost implications from different operational mitigation measures, like flying at reduced flight level and Mach number, lateral rerouting to avoid climate sensitive areas and climate-optimized intermediate stop operations (ISO). While these operational strategies offer substantial mitigation potential, they often come with significant cost trade-offs. Extending existing accounting schemes to include non-CO2 aviation effects can help overcome implementation barriers. Technical advancements can achieve further mitigation, while policy design, such as such as phased or partial CO₂e accounting, can help to limit overall cost increases. Finally, we highlight the large uncertainties in non-CO2 modeling and propose strategies to mitigate uncertainty-related risks in climate policies. These include using ensemble weather forecasts to reduce risks due to errors in forecasting persistent contrails as well as implementing uncertainty-based CO2e accounting that relies on confidence levels in climate impact modeling. Embracing prevailing uncertainties on climate effect estimates will be a prerequisite for a successful and efficient implementation of trajectory optimizations, attaining confidence in overall climate effect reduction. Ongoing research and adaptable policies are essential to incorporate the latest scientific understanding and drive meaningful climate action in aviation. Airlines, ANSPs, weather services, and authorities need to work collaboratively to identify best practices for non-CO₂ mitigation. To facilitate this, we conducted stakeholder workshops to incorporate operational expertise, institutional perspectives, and practical constraints into the design of potential non-CO₂ policy measures.