Key points:
- Scientists and politicians fear that rerouting flights to avoid contrails may inadvertently make climate warming worse.
- A new study reveals that contrail avoidance would significantly decrease warming compared with continuing current flight routes.
- With improved contrail forecasting and real-world trials, contrail avoidance may make air travel more sustainable.
Contrails—the white lines left behind planes in the sky—trap heat in the atmosphere and can contribute to global warming. Efforts to minimize these contributions, such as rerouting flights, are known as contrail avoidance. However, weighing the benefits of avoiding contrails and the drawbacks of extra carbon dioxide emitted from flying a different route has proved challenging.
Now, a new study, published in Atmospheric Chemistry and Physics, builds on previous research to show that contrail avoidance would benefit the climate.
Researchers examined nearly half a million flights over the North Atlantic and estimated how much warming was caused by the carbon dioxide emissions from these flights and their contrails. First, they determined how current flight routes would warm the climate over time and found that flight and contrail emissions will cause about 17 microKelvins (mK) of warming by 2039 and 14 mK by 2119.
Next, the team simulated a situation where planes could avoid all contrails by rerouting and using 1% more fuel. In this situation, total warming would decrease significantly with a 5 mK reduction by 2039 and a 2 mK reduction by 2119. These reductions represent 29% and 14% less warming than without rerouting.
Researchers used nine different methods to measure the climate impact of contrail avoidance and found that rerouting would be good for the climate in most cases. While there is still uncertainty in predicting where contrails will form and how much warming they will cause, the team feels their findings are important.
“Rerouting flights to avoid contrails could in theory reduce the climate impact of aviation and make air travel more sustainable,” explained co-author Nicolas Bellouin, professor at the University of Reading. “Our findings lift a major obstacle against implementing contrail avoidance, but we need better forecasting and real-world trials to make this work in practice.”