Interview with Stephen Arrowsmith

What are the main challenges to addressing non-CO₂ emissions?

As with all other economic sectors, aviation is under pressure to reduce its emissions in order to contribute to the EU objective of reaching climate neutrality by 2050 and ICAO's goal for international aviation of net-zero carbon emissions by 2050.

The climate impact from aviation emissions stems from a combination of both CO₂ and non-CO₂ emissions. In order to identify a robust decision-making process and ensure a policy or operational mitigation measure has the intended effect, the gaps in our understanding of the science of and impacts from non-CO₂ emissions need to be addressed. This includes accurate modelling of non-CO₂ emissions from different fuels and engine technology as well as the subsequent direct and indirect climate effects. These challenges are further compounded by potential trade- offs between CO₂ and non-CO₂ emissions, which can vary depending on the metric and time horizon selected. As such, identifying an optimum strategy to mitigate the overall aviation climate impacts requires considerable research and coordination.

Can you explain the purpose of the Aviation Non-CO₂ Experts Network (ANCEN) and what the experts are currently working on?

In order to bring greater cohesion to the various European research initiatives in this area, the European Commission and EASA set-up the ANCEN in June 2024. The primary goal of the Network is to facilitate a holistic approach to addressing non-CO₂ emissions through coordination across a wide range of relevant stakeholders (e.g. scientific / research community, manufacturers, aircraft operators, fuel producers, air navigation service providers, non- governmental organisations, regulators and policymakers). The Network aims to reach a common understanding on issues that can act as a basis for objective, timely and credible technical advice. This would feed into discussions on the development, agreement and implementation of effective policy and operational actions within Europe and internationally, to mitigate the overall climate impacts caused by aviation taking into account CO₂ and non-CO₂ emissions. The ANCEN website contains information on the Terms of Reference, list of Members, Work Programme, as well as links to related content. Details on deliverables will also be published on the website to support the wider discussions on the topic of non-CO₂ emissions. To facilitate cooperation with International Partners beyond Europe, a presentation on ANCEN was also made at the recent ICAO non-CO₂ symposium.

Which research findings do you find most instructive and what strategies and technologies are being explored to reduce non-CO₂ emissions in aviation?

There are already some mitigation measures in place to reduce non-CO₂ emissions, such as the ICAO aircraft engine emissions certification standards implemented by EASA in the EU, and the uptake of cleaner fuels (e.g. Sustainable Aviation Fuels) through the ReFuelEU Aviation Regulation.

Looking ahead, what can we expect from ANCEN in the months to come?

An initial work programme was agreed at the initial ANCEN meeting in June 2024. It includes:

• Establish a common terminology to facilitate stakeholder discussions;
• Develop a framework to communicate the level of uncertainty as a confidence level and likelihood for risk assessment, and monitor how this evolves over time;
• Identify elements of a process to develop and validate impact assessment capabilities that are needed to support robust decision-making and implementation / review of mitigation measures;
• Perform a gap and prioritisation analysis, and maintain over time, to optimize future aviation related research in critical areas and avoid duplication;
• Maintain an overview of historic and on-going work linked to the effects of aviation non-CO₂ emissions on climate change;
• Clearly communicate on the climate impacts of short- term and long-term climate forcing emissions to place non-CO₂ impact in context with CO₂; and
• Outreach to relevant international partners (e.g. ICAO, States, Industry) working on the topic of climate impacts from aviation non-CO₂ emissions to support coordination at a global level.

And a more general question on aviation's environmental challenge: In your opinion, what can aviation actors, from airspace users to airports, to policymakers and EUROCONTROL, do to make aviation more sustainable faster?

There is a growing urgency to address the sustainability challenges that the aviation sector faces and a concerted effort is required to secure the future of the industry.

This has been acknowledged within Europe and there are significant new initiatives under the new European Green Deal. There is no single solution and the entire basket of measures (e.g. new technology, efficient operations, sustainable aviation fuels, market-based measures) needs to be applied.

The challenge for the aviation sector now is to turn sustainability goals into action. The next edition of the EASA European Aviation Environmental Report, developed in cooperation with the European Environment Agency and EUROCONTROL, will be published in January 2025 and will provide an overview of progress to date and the way forward.

About European Union Aviation Safety Agency - EASA

The European Union Aviation Safety Agency (EASA) is the centrepiece of the European Union's strategy for aviation safety. The organisation's mission is to promote and achieve the highest common standards of safety and environmental protection in civil aviation. Based in Cologne, the Agency employs experts and administrators from all over Europe.