When thinking of flying's environmental impact, the CO2 emitted from burning jet fuel is usually what springs to mind. But there's another, lesser understood climate culprit hiding in plain sight: condensation trails.

The wispy, cloud-like formations left by airplanes as they traverse the skies may look innocuous, but the climate impact from 'contrails' could be similar to aviation CO2.

"I'm actually more worried about contrails at this point than I am about CO2 emissions because it is an impact that has not been internalized by the industry in any shape or form," said Jayant Mukhopadhaya, a lead aviation researcher for the International Council on Clean Transportation (ICCT), a US environment think tank.

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A 2021 study suggests contrails and other non-CO2 emissions could account for up to two-thirds of aviation's total climate impact. Contrails could represent 57% of that impact — roughly the same as CO2 emissions from burning fuel.

The aviation industry is currently thought to be responsible for 2 to 3.5% of global CO2 emissions annually.

"But if you start taking into account these other pollutants that aviation is responsible for, the aviation sector is actually accounting for a far higher amount of warming than we usually ascribe to it," said Mukhopadhaya, adding that it could be three times greater than previously assumed.

Contrails form when airplanes fly through very cold, humid pockets of air in the upper atmosphere. When plane engines burn jet fuel, water vapor condenses on particles from the air and exhaust to form ice crystals. If there........

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