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Contrails in Focus

18 December 2023

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Philippe Merlo, EUROCONTROL European Green Sky Director opening the EUROCONTROL-CANSO Sustainable Skies Conference

From 7-8 November the EUROCONTROL- CANSO Sustainable Skies Conference: Contrails in Focus brought together over 2,000 scientists, researchers, aviation representatives, policy makers and others to enhance the understanding of contrails and contrail-induced cirrus clouds, their impact on the climate, and to explore potential mitigation measures to minimise their occurrence.

"In the face of climate crisis, action is crucial. Our mission is to lay out a comprehensive path forward based on research, innovation and collaboration. We want to reduce contrail effects but also ensure that aviation remains an enabler of global connectivity, driving economic & societal progress." EUROCONTROL European Green Sky Director Philippe Merlo said in his opening statement to the conference.

Michelle Bishop, Director Programmes at CANSO echoed the importance of cooperation for aviation to achieve its climate goals and tackle the challenge of non-CO₂ emissions: “The mitigation of aviation's impact on the climate will take the collective efforts of all of us,” she said. "It is part of the larger challenge of ensuring our industry's future and our planet's future."

Michelle Bishop, Director Programmes, CANSO

Following the keynote introductions, Matthieu Plu from Météo-France and Klaus Gierens from DLR explained to the audience what contrails and contrail-induced cirrus clouds are, how and under which meteorological conditions they form, their physical properties and how they impact the climate. The many questions following the first session underlined that contrails are a subject the aviation sector and others are still trying to fully comprehend. What became clear is that new technology aircraft while significantly reducing CO₂ emissions actually may – under specific circumstances - produce more contrails. So, one of the key challenges the sector is faced with is to find the right solutions that tackle the reduction of CO₂ emissions and non- CO₂ emissions while not reinforcing the other.

The session on critical aspects of contrail avoidance with Keith Shine and Nicolas Bellouin, both from Reading University and David S. Lee, Manchester Metropolitan University demonstrated that the understanding of contrail climate effects is evolving but that for the moment, there is no guarantee that anticipated avoidance manoeuvres will not have a greater impact on the climate.

State-of-the-art methods for detecting and monitoring contrails and the technical challenges were discussed with a wide range of experts from Google, Massachusetts Institute of Technology (MIT), Airbus, EUROCONTROL, DLR and Thales demonstrating more research is needed to gain knowledge. It is one of the reasons why EUROCONTROL has launched ContrailNet- the new network to create a common repository of contrail observation data to advance the aviation sector’s efforts to reduce the climate impact of non-CO₂ aviation emissions, in particular contrails

Andreas Boschen, Executive Director, SESAR 3 Joint Undertaking

The data repository will be made available to existing and future research initiatives for them to develop their own contrail identification and evaluation algorithms. Besides EUROCONTROL's contrail prevention trials and our contrail observatory, this technical project is another component in EUROCONTROL's strategic work on non-CO₂ climate impacts. Philippe Very and Gabriel Jarry, both from EUROCONTROL, announced the new initiative during the EUROCONTROL-CANSO Sustainable Skies Conference.

Experts from Météo-France, Air France, German National Meteorological Service (DWD), DLR, Imperial College and Google shared insight into the current methods and technologies for predicting the formation of contrails and estimating their impact on the climate. The conference also gave an overview on ongoing contrail research projects and how they contribute to addressing unanswered questions. “Our projects into contrails cover both exploratory and industrial research. A core objective of these projects is to investigate how to obtain MET services capable of predicting the eco-sensitive areas and then monitor the evolution in real time,“ Andreas Boschen, Executive Director at SESAR 3 Joint Undertaking summarised SESAR 3 research priorities on contrails. He stressed further: “Sustainability is our focus. Our aim is to make Europe the most efficient and environmentally friendly sky to fly in.”

Laurent Donceel (Airlines for Europe), Patrick Arpino (European Cockpit Association), Steven Moore (EUROCONTROL), Jo Dardenne (Transport &Environment), Dimitar Nikov (European Commission), Vincent De Vroey (ASD), Vincent de Haes (To70), Marylin Bastin (EUROCONTROL)

Dimitar Nikov from DG CLIMA at the European Commission presented the plan for establishing a Monitoring, Reporting and Verification (MRV) scheme of aviation’s non-CO₂ effects, in support of the preparation of implementing legislation defined in the EU ETS Directive. The session set the scene for the following panel discussion on MRV which brought operational challenges into focus as rerouting aircraft to avoid regions favourable to persistent contrails formation may help the climate, but would add extra traffic to already congested airspace - causing additional delay and possibly more emissions. Yet, the discussion also stressed that the challenge of non- CO₂ can be an opportunity for aviation.

The conference discussions have been assembled in one document outlining the latest advancements in contrail science and mitigation. It will be made available together with the presentations and the recording of the conference on the event’s webpage