Contrails.org: Our Journey So Far

As we outlined in our first notebook post, research so far paints a clear picture of the climate opportunity that contrail management presents; it would make a huge impact, and relatively speaking, would be a simple fix compared to other decarbonization challenges. The scientific journey leading us here has been fascinating - but it’s far from over. To make contrail management a practical reality, we still need to proactively advance the science in specific areas, so we can build effective tools, and better understand and predict cause and effect when it comes to routing and contrail formation.

This is why Contrails.org is pursuing a research agenda across four pillars: evaluation datasets, modeling capabilities, assessment frameworks, and tool development. As a small team, our mission is to conduct, coordinate, support and sponsor strategic research. We aim simultaneously to better model, predict and measure contrail formation, and also to ensure that the correct tools exist and are properly integrated into operators’ platforms to rapidly enable solutions. We’ve come a long way already, and established a solid foundation; this post offers a brief retrospective of some of the research and results we are most proud of accomplishing.

Origins and Evolution 

The interest in contrail avoidance being a potentially huge climate win was made clear by the paper "Beyond Contrail Avoidance: Efficacy of Flight Altitude Changes to Minimise Contrail Climate Forcing" by Roger Teoh, Ulrich Schumann, and Marc Stettler. This research explored how small-scale flight altitude adjustments could effectively reduce contrail formation, offering practical strategies for airlines to mitigate their environmental impacts. Prior to this paper, contrail impacts were already known to be large, but this paper emphasized that mitigation should be possible with extremely minimal operational impacts. At the time this paper was written, Roger was a Ph.D. student of Marc at Imperial College. Roger has since graduated, and Roger and Marc have become core members of our team. Ulrich Schumann, a Professor at DLR (Deutsches Zentrum für Luft- und Raumfahrt, the German Aerospace Center), remains a close collaborator. 

Notably, this paper gained the attention of Ian McKay, the leader of Orca Sciences, a small climate and energy think-tank sponsored by Gates Ventures, and Ken Caldeira, Senior Scientist at Breakthrough Energy. Their commentary in Nature highlighted the fact that contrail management is a super cheap climate intervention that might be realistically achievable. Inspired by this work, the group that would eventually become Contrails.org initially formed under Orca Sciences through Ian’s leadership, before transitioning to being hosted by Breakthrough Energy, where it has continued to expand its research and impact, and growing a large consortium of academic and industry partners.

Pioneering Research and Publications

From the beginning, it was clear that the most urgent research priority was to make sure we had models to forecast contrail formation in real time. Our starting point was the original CoCiP (Contrail Cirrus Prediction) model, developed by Professor Ulrich Schumann at DLR, The German Aerospace Center). The original CoCiP tool, which we now refer to as “trajectory CoCiP”, simulates contrails along individual flight paths. While this makes it useful for estimating contrail impacts of flights that have already occurred, it is not suited for use in flight planning. Our adaptation of the original CoCiP model, named CoCiP-Grid, approximates this method by evaluating contrail formation and climate impact over a 4D spatiotemporal grid, enabling faster and scalable computations across entire airspace regions. This innovation made it possible to integrate contrail-aware route optimization directly into flight planning and air traffic management systems, allowing airlines to reduce contrail climate impact with minimal fuel penalties.

Another major result of our group was the publication of the GAIA dataset which utilizes historical flight trajectories from Automatic Dependent Surveillance–Broadcast (ADS-B) data and reanalysis weather information to develop a detailed aviation emissions inventory for the years 2019 to 2021. The publication of this dataset required the careful curation of multiple years of aircraft trajectories, which then were all separately run through the CoCiP trajectory tool to create a global inventory of contrail impacts and aviation missions. This high-resolution dataset is crucial for accurately assessing the environmental impact of aviation and informing strategies to mitigate its negative externalities. In 2019, the inventory recorded 40.2 million flights covering 61 billion kilometers, consuming 283 million metric tonnes of fuel, and emitting 893 million tonnes of CO₂, 4.49 million tonnes of NOₓ, 21,400 tonnes of non-volatile particulate matter (nvPM) mass.

Notably, we also worked with a team from FlightKeys, a global flight planning service provider to integrate contrail forecasts into a commercial-grade flight planning system. We worked together to perform a fleet-wide simulation of contrail avoidance to assess the feasibility and operational impacts of contrail avoidance. This research, published in early 2024, demonstrates that contrail formation can be reduced by up to 59% with a minimal fuel penalty of as low as 0.5%. This approach offers a practical solution for airlines to significantly decrease their environmental footprint without substantial increases in operational costs or fuel consumption.

Innovative Tools and Open-Source Contributions

To facilitate actionable solutions, contrails.org has developed open-source software tools that accurately forecast and verify contrail impacts. These tools empower the aviation industry to implement more sustainable flight plans by predicting contrail formation and suggesting optimal flight paths to minimize environmental harm. Among these contributions, the team has published CoCiP-Trajectory and CoCiP-Grid within the pycontrails framework, making cutting-edge contrail modeling more accessible and practical for researchers and industry stakeholders. The team maintains an API from which industry and academic partners can easily access model outputs.

Additionally, contrails.org has played a key role in shepherding the development of the Poll-Schumann model into an open-source aircraft performance model integrated within pycontrails. By working closely with Ian Poll and Ulrich Schumann, the project has made substantial progress and creating a commercial-grade aircraft performance model openly available to the research community. Work is ongoing to continue to expand the PS model to encompass more aircraft types and further refine the accuracy of the model.

Collaborations and Industry Impact

The practical application of Contrails.org's research is exemplified through collaborations with major industry players. In 2023, American Airlines, in partnership with Google Research and Breakthrough Energy, participated in a groundbreaking study to test contrail avoidance strategies. Over six months, American Airlines pilots conducted 70 flights using AI-based predictions to adjust routes likely to produce contrails. The results were promising, achieving a 54% reduction in contrail formation with minimal additional fuel consumption.

This collaboration not only demonstrated the feasibility of contrail avoidance but also highlighted the potential for scalable climate solutions within the aviation industry. Such partnerships are crucial for translating scientific research into real-world applications that can significantly reduce aviation's environmental impact. We are excited to continue our collaborations with operational partners to expand real-world testing and implementation of contrail avoidance.

Global Recognition and Media Coverage

The innovative work of contrails.org has garnered attention from leading media outlets and scientific communities. Publications such as The New York Times, MIT Technology Review, and Nature have featured their research, bringing broader awareness to the issue of contrail-induced warming and the efforts to combat it.

Looking Ahead

As contrails.org continues to advance its mission, the focus remains on expanding collaborations with airlines, policymakers, and researchers to implement contrail mitigation strategies globally. By leveraging cutting-edge research and technology, the team aims to make contrail avoidance a standard practice in aviation, thereby contributing to a more sustainable future. Our group, Contrails.org, has made remarkable progress in understanding and mitigating the climate effects of contrails. Stay tuned for future posts outlining what we see as the way ahead for the industry.