A brand new study allays fears that rerouting flights to avoid forming climate-warming contrails could lead to inadvertently making climate warming worse.
Researchers from Sorbonne Universite and the University of Reading found that for many flights that form contrails within the North Atlantic, the climate advantage of avoiding the contrail outweighs the additional carbon dioxide emitted from flying a special route.
Contrail avoidance requires comparing the climate impacts of carbon dioxide and contrails, called CO2 equivalence. Different methods have been proposed, and the alternative of which has been largely political. Scientists feared that some decisions could possibly be misleading, making avoidance seem useful for climate when it’s in actual fact damaging.
The study, published today (Sunday, 15 September) in Atmospheric Chemistry and Physics, finds that for a big majority of North Atlantic flights, contrail avoidance would profit climate whatever the alternative of CO2 equivalence.
Contrails explained
Contrails — the white lines left behind planes within the sky — can trap heat within the atmosphere and contribute to global warming.
The brand new study builds on previous research that suggested planes could possibly be rerouted to avoid contrail formation, potentially reducing climate impact. Nonetheless, the advantages of avoiding contrails against the drawbacks of additional CO2 emissions were unclear.
Prof Nicolas Bellouin, co-author on the University of Reading, 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 significant obstacle against implementing contrail avoidance, but we now need higher forecasting and real-world trials to make this work in practice.”
The brand new findings show that no matter how the trade-off between contrail avoidance and increased CO2 emissions is measured, rerouting rarely worsens climate effects unintentionally. The study checked out nearly half 1,000,000 flights over the North Atlantic in 2019 to estimate how much warming was brought on by the carbon dioxide emissions from these flights and any contrails they formed.
The researchers first examined how current flight routes would warm the world over time. They estimate that the CO2 emissions and contrails from these flights may have warmed the climate by about 17 microKelvins (μK) in 2039, 20 years later, and 14 μK in 2119, 100 years later. A microKelvin is a really tiny unit of temperature change.
Then the researchers imagined a situation where planes could avoid all contrails by utilizing just 1% more fuel. On this case, the full warming would decrease significantly. By 2039, warming can be reduced by about 5 μK, which is 29% lower than without rerouting. By 2119, it might be about 2 μK (14%) less.
The researchers used nine other ways to measure climate impact. Normally, all these methods agreed that rerouting flights can be good for the climate, so long as the planes successfully avoid contrails as predicted.
The researchers emphasise that there remains to be much uncertainty in predicting exactly where contrails will form and the way much warming they cause. They suggest focusing initial rerouting efforts on flights that form probably the most warming contrails, where the climate profit is clearest.
