Adam Morton, Head of Technology – Sustainability & Strategy, considers the UK’s unique resources and capabilities in avoiding contrails from aircraft and why now is the time to take a leadership role in airspace-led trials.
There is growing evidence that airlines can use flight path variation to avoid generating persistent warming contrails. It is equally likely that this mitigation can be achieved with a very modest fuel burn and carbon dioxide (CO₂) emissions penalty. However, further research is needed to analyse these trade-offs.
The latest research indicates aviation may account for about 3.5% of anthropogenic radiative forcing, with contrails accounting for around half of this effect. Put another way, contrails may drive 1-2% of the total global warming from human activity. At the same time only a small proportion of all flights, possibly 2-3%, are responsible for 80% of that contrail warming. This is because the vast majority of flights do not encounter Ice Super Saturated Regions (ISSRs), where all the necessary conditions for persistent contrails combine. Given that ISSRs are relatively thin layers in the atmosphere, it could be feasible to plan flight-routes with small altitude changes to fly above or below them.
What trials have been undertaken so far?
The testing of such ideas is not entirely new with numerous contrail avoidance trials undertaken in the last decade. Such work, with inputs from air navigation service providers (ANSPs), airlines, academia, leading research institutes and technology companies, has already partly demonstrated the concept. In most cases, these trials showed fewer contrails and the potential for lower contrail-induced warming. The findings regarding CO₂ were more mixed. However, even accounting for modest extra fuel burn, the carbon dioxide equivalent (CO2e) benefits were highly significant.
It is also worth recognising today’s flight routes are not optimised for fuel burn and that routing inefficiencies often increase flight distances. Resulting innovations in airspace management could also permit reduced aircraft fuel burn, CO₂ savings and lower airline costs. While further work is necessary on other effects, findings to date indicate contrail avoidance would only have modest impacts on flight duration and scheduled take-off and landings.
How would future trials be different ?
Most of the contrail avoidance studies delivered so far have been airline-led trials in which a small number of airlines have designed and undertaken the demonstration. This approach has delivered valuable insights on the science of contrail avoidance and helped mature some technology and operational needs.
Now, further trials are needed to fully evaluate the impact of contrail avoidance at large scale. This will require air traffic controllers to centrally manage contrail avoidance measures for all flights operating in a given airspace. This would build on existing work and combine oceanic and domestic airspace and include both short-haul and long-haul flights. Such trials would be orders-of-magnitude larger in scale than anything previously, thus filling gaps in scientific understanding, validating systems and building confidence. Clearly, maintaining safe and reliable routes will remain the priority and it may be necessary to schedule trial-phasing to avoid certain time periods.
Such work will validate critical contrail-related scientific work in the UK and further afield. It will also help confirm the ability of relevant systems and processes to accommodate extra dynamism in flight planning. Most importantly, it will inevitably help to pull through key aerospace and space technologies. These are likely to include imaging, satellite systems, contrail ID, modelling and artificial intelligence (AI).
So, why lead from the UK?
One of the key characteristics of contrails is their greater tendency to form at high latitudes. The northerly position of the UK and Europe means the region’s departing flights have a disproportionate contribution to contrail formation. By some estimates, the North Atlantic accounted for 5% of the total flight distance flown in 2019 but 10-11% of the annual contrail warming effects.
With NATS handling over 2.5 million flights travelling over the UK and across the North Atlantic every year, it has the unmatched ability to support contrail avoidance through sustainability-driven routing. For instance, trials could focus on North America bound flights travelling through the Shanwick and Scottish airspace areas.
Other factors that favour UK leadership here include weather modelling expertise in the Met Office, UK academic strength in the area and ongoing crucial support from the UK government. The latter is evident not only through associated non-CO₂ funding by the Aerospace Technology Institute and the Natural Environment Research Council (NERC), but also a renewed contrail focus by the Jet Zero Taskforce.
Why start trials right away?
Unlike CO2 which causes long-term warming over centuries, contrails have a larger but short-lived warming effect, lasting only hours before dissipating. As a result, measures introduced in the near-future can have an immediate cooling effect. Work by the University of Cambridge concludes contrail avoidance could be deployed at scale as early as 2030 if trial results look promising. Although five years away, any such programme would require considerable preparation and coordination between airlines, NATS as the ANSP, academia and providers of the necessary imaging and data analysis technology. Further complicating any scheduling is the seasonal nature of contrails. In the Northern hemisphere, warming contrails are more prevalent in the autumn and winter months making inclusion of these essential.
The UK has a key role to play in this emerging area of non-CO₂ mitigation. We welcome applications that align with the ATI Non-CO₂ Technologies Roadmap and that contribute to the development of innovative capabilities in this critical area. Our aim is to support research and technology advancements that address non-CO₂ climate impacts to position the UK as a global leader in non-CO₂ emissions R&D. Further information on the Non-CO₂ Programme including how to submit a funding application can be found here.