WASHINGTON — The federal government should pursue a national research agenda to enhance understanding of contrails and investigate potential strategies for mitigating their contributions to atmospheric warming, says a new report from the National Academies of Sciences, Engineering, and Medicine. Doing so would help maintain the global economic competitiveness of the U.S. civil aviation industry, given emerging international aviation regulations, particularly in Europe.  

Contrails are the visible lines left in the sky behind aircraft when warm jet-engine exhaust meets the colder surrounding atmosphere, forming small ice crystals. Most contrails dissipate within about 10 minutes, but they can last for hours under certain conditions. Contrails can contribute to atmospheric warming and, at scale, contrail warming effects are of similar magnitude to the warming effects of the aviation industry’s emissions from fossil jet fuels.  

The U.S. has long been a leader in all aspects of aviation. As international climate regulations are established that aim to lower the industry’s sizable contributions to atmospheric warming, the U.S. needs to proactively work to maintain the global competitive posture of its airlines, aircraft manufacturers, and fuel producers. The U.S. risks these sectors falling behind those of other countries if it does not adequately support research and technology development in this area, the report warns.  

Research into the causes of persistent contrails, methods and systems to model their effects, and the potential impacts of factors such as use of synthetic fuels and new propulsion systems will allow the U.S. to develop the improved technologies, forecasting abilities, and operational flight procedures needed to mitigate contrail formation and maintain competitiveness of the U.S. aviation industry. The report says that NASA’s experience helping to develop new commercial technologies, ability to coordinate across agencies and industries, and history of contrails research make it well suited to lead these efforts.  

“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,” said Timothy Lieuwen, Regents’ Professor and executive vice president of research at the Georgia Institute of Technology, and chair of the committee that wrote the report. “This practical research will lead to more cost-efficient data collection, advanced fuel and engine development, and more economical and environmentally friendly flight operations.”

Detection Tools and Forecasting Systems

Commercial aircraft report temperature and wind data to improve flight weather forecasting, but they do not currently provide measurements on water vapor in the atmosphere around the plane. Adding this capability is critical for improving scientific understanding of where contrails form and why they sometimes persist, the report says.  

NASA should support the development, testing, and certification of more advanced and accurate sensors for commercial aircraft, including humidity and temperature sensors and contrail-detection cameras that can provide data in near real time, along with improved image-recognition algorithms to automatically detect contrails, the report says. NASA should also support space- and ground-based sensing research needed to complement airborne sensors.  

Additionally, NASA has an Earth observation system that already takes in aviation temperature and wind data. This system could be modified to model contrail formation and persistence, providing a valuable tool for research, analysis, and verification efforts and a path to understanding how to better forecast contrails.

Advanced Technologies

Reducing the particulate emissions of commercial aircraft can play a key role in mitigating the environmental effects of contrails that linger in the atmosphere, the report says. NASA should coordinate with the private sector and relevant federal agencies to support the development of combustion system technologies, novel sustainable aviation fuels, and adjusted maintenance cycles and engine operating conditions that produce fewer particles.

Flight Operations

Efforts to improve understanding and forecasting abilities will open new possibilities for identifying airline operational changes that could reduce contrails. The report says NASA should collaborate with airlines and agencies such as the Federal Aviation Administration to research, develop, and evaluate concepts for rerouting commercial aircraft to avoid regions where persistent contrails are likely to form. Care should be taken to ensure that these methods are fuel efficient and minimize disruption to flights and air traffic control systems.  

The study — undertaken by the Committee on the Research Agenda for Reducing the Climate Impact of Aviation-Induced Cloudiness and Persistent Contrails from Commercial Aviation — was sponsored by NASA.  

The National Academies of Sciences, Engineering, and Medicine are private, nonprofit institutions that provide independent, objective analysis and advice to the nation to solve complex problems and inform public policy decisions related to science, engineering, and medicine. They operate under an 1863 congressional charter to the National Academy of Sciences, signed by President Lincoln.

Contact:

Josh Blatt, Media Relations Officer
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202-334-2138; email news@nas.edu