A cross-section of airlines, academic institutions and technology partners have joined forces to explore the formation and mitigation of contrails caused by commercial flying.
Contrails form when soot and water vapor emissions from jets mix with humid, cold air. When contrails linger, as they do in certain conditions, they trap heat in the atmosphere, becoming a cause of climate change.
Airline participants in the Contrail Impact Task Force include American, Southwest, Alaska, United and Virgin Atlantic. They’re joined on the task force by aircraft manufacturers Airbus and Boeing, Google Research, the Bill Gates-founded nonprofit Breakthrough Energy, the nonprofit climate research and policy advocate Rocky Mountain Institute, the Austrian flight planning and software company Flightkeys, and Imperial College in London (a leader in contrail formation research).
A 2021 study published in the peer-reviewed journal Atmospheric Science found that aviation is responsible for approximately 3.5% of global climate change, with contrails responsible for 57% of that impact
However, not all contrails are a problem. Persistent contrails, also known as contrail cirrus, are the ones that trap atmospheric heat. The good news is that only a small percentage of flights cause those contrails. A 2021 study conducted jointly by the German Aerospace Center and Eurocontrol found that 10% of flights are in the areas where warming contrails form.
Especially problematic are contrail cirrus that form at night. While persistent contrails can both trap heat and reflect the sun’s radiation during the day, contrail cirrus that form at night only trap heat.
A challenge for airlines, however, is that conditions agreeable for the formation of those long-lasting contrails tend to occur at between 30,000 and 40,000 feet, which is where commercial airlines fly to maximize fuel efficiency.
Still, avoiding flying in areas that are ripe for contrail formation, a practice known as contrail avoidance, could offer a quick way for airlines to reduce their climate impact.
The issue is just beginning to become a point of emphasis for airlines.
Recently, Delta announced a partnership with MIT to study contrail avoidance. Etihad trialed contrail-avoidance technology early this year.
The Contrail Impact Task Force will work to share and expand research on the climate impact of contrails. In addition, participating airlines will work toward turning that science into actionable changes. They’ll do that by analyzing the financial and operational challenges of implementing potential solutions, such as incorporating contrail forecasting into flight planning.
“The Contrail Impact Task Force will enable vital cross-sector collaboration, allowing us to better understand the science of contrails and, ultimately, to take action to address the issue,” said Lauren Riley, United’s chief sustainability officer.
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