E-CONTRAIL publishes its Policy Brief: Making Contrails Visible

Today is a milestone day for E-CONTRAIL.

Making Contrails Visible: AI-Based Insights into Aviation’s Climate Impact using Satellite Imagery. E-CONTRAIL project Policy Brief.

We are thrilled to publicly release our Policy Brief and the illustrated comic embedded within it, “A real contrail story…” summarizing the scientific results, key conslusions, and policy recommendations of the project.

After two years of research, engineering, and iteration, we can now say it clearly:

Policy actions should prioritize flights generating contrails at night, in winter season, with a strong focus on the southern north atlantic region.

Using AI and satellite imagery, E-CONTRAIL systematically detected, classified, and quantified contrails across the Euro-Atlantic region , year-round, at scale.

This generates an evidence base that re-frames how we should think about mitigation.

Four decisive policy recommendations emerge:

1. Prioritize mitigation actions for flights occurring at dark (or mostly at dark):

   The project confirms that contrails formed at night, or on flights that take place mostly at night,exert a net warming effect by trapping longwave radiation without an offsetting shortwave cooling component. Therefore, mitigation strategies should be prioritized for nighttime operations to selectively avoid the formation of these consistently warming contrails.

   
   

2. Prioritize contrail mitigation actions during winter months.

   The radiative forcing of contrails shows a strong seasonal dependency. A significant net

   warming impact is observed during the autumn and, most markedly, the winter months.

   Mitigation efforts should be strategically focused on flights during these periods. Conversely, mitigation appears less critical in summer when both contrail frequency and impact are lower. Due to significant uncertainties in the net forcing effect during spring, imposing mitigation measures in these months is not recommended without further research.

   
   

3. Focus Special Attention on Oceanic Flights:

   Contrails are more common over the oceanic regions, where aircraft typically cruise at higher altitudes for longer durations, and the upper atmosphere is both colder and more humid. A large share of contrails occurs over the southern North Atlantic oceanic regions, where dense transatlantic flight routes favor their formation. In contrast, central Europe’s drier upper atmosphere and shorter flight paths lead to fewer or less persistent contrails.

   
   

4. Invest in Fundamental Contrail Research to Close Knowledge Gaps:

   An accurate, trustworthy Monitoring, Verification, and Reporting (MVR) scheme for aviation's non-CO2 impacts is essential for effective climate policy. Achieving this requires continued and significant investment in fundamental research. Priority areas related to contrail research should include, among others, novel contrail models, advancing satellite-based detection and radiative forcing estimation algorithms, expanding observation means, constructing and sharing labelled datasets, identifying flight attribution techniques to link specific contrails to their originating flights, developing robust contrail avoidance schemes in flight planning.

This is new evidence for climate-aligned aviation policy.

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Thank you.

To the full E-CONTRAIL consortium:

• Universidad Carlos III de Madrid (ES) — Project Coordinator

• Royal Belgian Institute for Space Aeronomy (BE)

• KTH Royal Institute of Technology (SE)

• Royal Meteorological Institute of Belgium (BE)

  
  

Special thanks to SESAR 3 Joint Undertaking for funding, trust and enabling this European effort.

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And if you want to explore it yourself: you can download the full Policy Brief and the comic (spanish version).