THE UNIVERSITY of Reading has found that rerouting flights to avoid contrails could help efforts to tackle climate change, according to a new study.
The university worked with researchers from Sorbonne Universite on a study into how rerouting flights to change contrails affects efforts to reduce global warming.
Condensation trails, the white streaks left in the wake of aircraft during flight, are made of condensed water vapor created by jet engines.
This trail only forms under certain conditions– most commonly at cruising altitude for commercial flights, which is between around 32,000 and 42,000 feet, with cool air and a certain level of humidity.
Hot vapor left by the engines cools and can last for hours, with the potential to trap heat radiated from the surface of the planet in the atmosphere, known as the greenhouse effect.
While they are not dangerous to humans, they can contribute to global warming.
The study examined the proposition that rerouting flights to change where contrails form could change how they affect global warming.
Previous research in the field posited that avoiding the leaving of contrails would reduce their impact on global warming.
The research interrogated this theory, finding that the increased emissions of carbon dioxide (CO2), which is also a greenhouse gas, was outweighed by the reduction in global warming from the trails.
It compared the impact on the climate of both contrails and carbon dioxide– also known as CO2 equivalence– and found that the benefit of avoiding contrails was not disproportionately mitigated by the increase in CO2 emissions.
Researchers examined how current routes of nearly 500,000 flights in 2019 would warm the Earth over time, drawing an estimation of how much global warming was caused by both the carbon dioxide emitted and the contrails left.
They then drew up a framework scenario where all contrails could be avoided by using just 1% more fuel and measured the resulting climate impact using nine separate measurements of climate impact.
As long as flights were able to reduce contrails as expected, the framework showed that rerouting flights would be effective in reducing impact on the climate “significantly.”
However researchers from the study, which was published in Atmospheric Chemistry and Physics on Sunday, September 15, emphasised that there was still “much uncertainty” in predicting where the trails form and how much they affect the climate.
The study suggests that focusing rerouting efforts on the most warming flights and contrails would provide the clearest benefits to reducing global warming.
Researchers now suggest that more real-world trials and improved forecasting is needed to better evaluate the effectiveness of rerouting in global warming reduction.
Prof Nicolas Bellouin, at the University of Reading, one of the study’s co-authors, said: “Rerouting flights to avoid contrails could in theory reduce the climate impact of aviation and make air travel more sustainable.
“Our findings lift a major obstacle against implementing contrail avoidance, but we now need better forecasting and real-world trials to make this work in practice.”
