DID YOU KNOW? These large cottony furrows, which crisscross the sky, have been the subject of much debate in the scientific community for several years.
They form small white scars in the sky. These long traces left by the passage of an airplane have a name: condensation trails. They form at the exit of the reactors, at a certain altitude, when the air is sufficiently cold and humid. “Contrails consist largely of water vapor (but also carbon and other residues from the combustion of fuel in aircraft engines) condensed due to the temperature difference created by the pressure difference between the upper and lower surfaces of the wings, wingtips or engines.”explains Greenpeace.
For several years, these white streaks, called “contrails”, have been the subject of much debate. They are in fact the hidden face of air transport, because they induce cirrus clouds, a form of very thin clouds, present over a large area, which can persist for several hours. The spectacle can delight amateur photographers, but it is in reality very bad news in terms of climate. Because condensation trails “increase the albedo [la part des rayonnements solaires renvoyés vers l’atmosphère, ndlr] of the atmosphere, and accentuate the greenhouse effect by retaining the infrared rays emitted at night“, explains Onera, the French aerospace research center.
Source of global warming
Which has direct consequences. According to a study published in 2021, these “contrails” are the main contributor to global warming caused by aviation. However, at a time of increasing air traffic, their effect is never taken into account by airlines or the Directorate General of Civil Aviation (DGAC) when they calculate their carbon footprint. Scientists and engineers are trying to find solutions. The use of alternative fuels could significantly reduce their presence. But while waiting for this energy to become more widely available, some researchers are proposing to fly planes at a slightly different altitude. The aim: to limit the appearance of these white clouds, which, behind their aesthetic appearance, are just as harmful as carbon dioxide.
It is also a way to put an end to conspiracy theories. For some, these large cottony furrows are used to spread chemicals on populations, for others, these chemtrails (short for “chemical trails”) are above all a tool to secretly control the climate.
