New National Research Agenda to be Developed to Tackle Contrails
U.S. National Academies Seeks to Better Understand the Climate Effects of Contrails
The National Academies of Sciences, Engineering, and Medicine has released a major new Consensus Study Report titled "Developing a Research Agenda on Contrails and Their Climate Impacts". The report outlines a national research agenda aimed at addressing the substantial climate impact of persistent contrails formed by aircraft by endeavoring to understand the key mechanisms involved in contrail formation, and to refine the processes for weather forecasting and contrail prediction, which could lead to a reduction in their climate impact.
This study was undertaken at the request of NASA in early 2024. The objective was to “develop a national research agenda to better understand, quantify, and support the development of technical and operational solutions to significantly reduce the global climate impact of aviation-induced cloudiness and persistent contrails from commercial aviation.”
The report presents priorities for this national contrails research strategy and provides an outline for how this research could bridge the knowledge gap on the full scale of the climate impact of contrails and support operational contrail mitigation. The findings are also seen as relevant to the economic competitiveness of the U.S. civil aviation industry, particularly in light of emerging international regulations on aviation's climate impact – like the EU’s MRV Framework.
As a Consensus Study Report, the document represents the evidence-based consensus of an authoring committee of experts and includes findings, conclusions, and recommendations. The report indicates that the research agenda will delve into critical areas such as:
Aircraft Engine Emissions (Chapter 2): This focuses on the role of jet engine exhaust in contrail formation. It covers important information related to general combustor emissions, lubrication oil vent effects, and the particle impacts on contrail formation and downstream aerosol-cloud interactions – juicy subject matter, indeed.
Atmospheric Measurements (Chapter 3): This section dives into the data needed to understand contrails and their environment. It tackles the measurements of atmospheric state parameters, atmospheric particles, and contrails and contrail cirrus themselves.
Contrail Modeling Systems (Chapter 4): This chapter addresses the computational tools necessary for simulating and predicting contrail behavior. The critical aspects discussed here emphasize the refining of various models, including: wake vortex, global climate, contrail plume, and ice supersaturation forecast models, as well as systems for contrail prediction.
Contrail Forecast and Verification (Chapter 5): This area is dedicated to the practical application of contrail understanding and modeling for creating usable forecasts. It considers the purpose of a contrail forecast system, examines existing contrail forecast systems, covers ice supersaturated region nowcasting/ forecasting and contrail forecasting specifically, outlines evaluation methods for these forecasts, describes what a forecast system would look like, and addresses the challenges and opportunities in this field.
Operational Concepts (Chapter 6): This explores how the understanding, measurements, modeling, and forecasting developed through the research agenda can be translated into practical strategies and procedures for contrail reduction. It touches on policy developments, the benefits of contrail mitigation, the feasibility of contrail avoidance, and recent contrail avoidance trials performed by several organizations and airlines.
These areas of research substantiate the priorities of the agenda. It seeks to understand the direct outputs from aircraft engines and how different types of emissions and particles influence the formation and persistence of contrails. It highlights the need for robust observational data to characterize the atmospheric conditions under which contrails form and persist, as well as their properties and impact. Additionally, by focusing on developing and improving models that can simulate everything from the immediate formation of contrails in the aircraft wake to their broader climate effects, it can lead to better prediction of when and where persistent contrails are likely to occur.
Furthermore, the report points to research needed to develop reliable prediction systems that can predict areas where contrail formation should be avoided or is expected, and how to verify their accuracy. This improvement could facilitate operational changes like re-routing aircraft to avoid those contrail-forming regions, a promising field of work gaining traction in the aviation industry through various collaborative trials and simulations.
Speaking of collaboration, the chair of the committee that wrote the report, Timothy Liewen said, “A concentrated and collaborative approach to contrails research across the federal government, industry, and academia represents a real strategic opportunity to address a growing issue in aviation that airlines and manufacturers have to contend with.”
In keeping with Liewen’s words, the release of this comprehensive report signals a focused national effort to deepen the understanding of contrails and develop practical strategies to lessen their effect on the climate, charting a course for future research and potential changes in aviation operations.