3% of flights caused
80% of contrail warming
A new analysis by T&E shows that 25% of European aviation’s contrail-related global warming comes from night flights in autumn and winter, which make up just 10% of European air traffic.
Contrail warming is highly seasonal and concentrated in time: in 2019, 75% of European contrail warming occurred between January to March, and October to December and 40% during late evenings and nights. Combined, night flights in autumn and winter accounted for 25% of European contrail warming, with only 10% of air traffic. These periods create ideal conditions to adjust a small number of flights with minimal effects on air traffic and major climate benefits.
Contrails, the white lines left by planes in the sky, can spread and persist in certain atmospheric conditions. This traps heat and warms the planet at least as much as aviation's CO₂ emissions, contributing between 1% and 2% to global warming. Yet only 3% of flights caused 80% of this warming in 2019. Reducing contrails and the warming they cause could be easily achieved by adjusting the flight paths of just a few flights at specific times of the day and year.
Rerouting flights: a real opportunity
Contrails form as aircraft fly through regions of very cold, humid air. These emissions stay in the atmosphere and form clouds that act like a giant blanket, trapping heat from earth’s surface. Small route adjustments or minor climbs or descents, to avoid the cold and humid atmospheric regions, would significantly reduce contrail formation.
“Contrails are a very concentrated problem. Fortunately, there are straightforward and affordable opportunities to scale up contrail avoidance in Europe. The science and the solutions are clear: by adjusting the paths of just a handful of flights, Europe could prevent years of avoidable global warming”, Alexander Kunkel, Senior Analyst at T&E, explains.
The concentration of contrails not only occurs at specific times of the year, but also around specific locations. The study confirms that the North Atlantic has high contrail avoidance potential - indeed, the airspace above the North Atlantic is dominated by long-haul flights with high contrail warming but has low traffic density. Long-haul flights above five hours alone accounted for 40% of contrail warming while representing only 10% of European departures in 2019.
Contrail avoidance should happen first in regions with high warming but low traffic, T&E recommends. Avoiding contrails when traffic levels are below 60% of their annual peak could have addressed around 70% of European contrail warming in 2019, the study finds. Re-routing can be planned in advance using weather forecasting and before the flight takes off. This would reduce controller workload and ensure safe operations.
"The time to shift into the next gear on contrail action is now. By boosting research, supporting large-scale trials, and designing a policy framework, Europe can pave the way for the deployment of contrail avoidance in the next five to ten years,” Kunkel suggests.
To scale up contrail avoidance, T&E recommends that the EU:
-
Includes non-CO₂ effects and contrails into air traffic management (ATM) legislation.
-
Maintains the automatic extension of the EU’s non-CO₂ monitoring scheme to extra-EEA flights, to further improve data and research on contrails.
-
Incentivises airlines and air traffic control centres performing contrail avoidance.
-
Conducts large-scale airspace trials to develop better knowledge on contrail avoidance.
