The white, feathery lines behind airplanes that look like bits of harmless cloud are anything but, warn experts, who say they could have a greater environmental impact than the aviation sector's CO2 emissions.
The condensation trails -- contrails, for short -- are being increasingly studied as scientists work with the industry to find technological solutions to the problem.
Classified as non-CO2 emissions from aircraft, in September they were the subject of a symposium in Montreal organized by the International Civil Aviation Organization, a U.N. agency.
What are contrails?
Contrails are clouds that form at high altitudes in cold, humid areas called ice supersaturated regions (ISSRs).
When jet fuel is burned by engines, water vapor condenses on to soot particles to form ice crystals.
Enough ice crystals, and they begin to form cirrus clouds -- high-altitude, wispy white filaments that, when created this way, trail out behind planes as they cross the sky.
These trails trap some of the heat that rises from the Earth at night, preventing it from radiating back out of the atmosphere -- thus acting as a greenhouse gas, causing warming, explains Donald Wuebbles, a professor at the University of Illinois.
Contrails that stay in the sky for a few minutes are not very worrisome, he says.
"But if they form at night, they'll maybe last a little longer, and at night they can cause a warming effect," he adds.
What is the impact?
Non-CO2 emissions could account for up to two-thirds of aviation's impact on global warming, which "gives you an idea of how important they are to consider," Wuebbles said.
And contrails could form up to 57 percent of that impact -- far more than the C02 emissions from burning fuel, according to a 2021 study.
However, such emissions are short-lived compared to carbon dioxide and their impact on global warming could be quickly eroded if solutions were found to avoid them, experts say.
So what can be done?
Not all flights create contrails -- it can depend on weather conditions and the aircraft's trajectory.
For example, at Air France, just four percent of flights are responsible for some 80 percent of the airline's contrail impact on global warming, notes Irene Boyer-Souchet, who is leading up the company's efforts to mitigate the damage.
The long-term strategy is to modify the trajectory of a fraction of flights.
Air France pilots made more than 3,000 observations over 18 months with the aim of helping Meteo-France improve its forecasts for at-risk areas so that pilots could eventually avoid them.
"The main risk is that by thinking you're avoiding an area, you could end up flying there because it's slightly off the weather forecast," Boyer-Souchet points out, illustrating the importance of fine-tuning the research.
Pilots from American Airlines conducted 70 test flights above or below at-risk areas, guided by satellite images, weather data, software models and AI prediction tools.
A 54-percent reduction in contrails was observed, along with a two-percent increase in fuel consumption.
Accelerating the deployment of a global contrail avoidance system could reduce aviation's impact on the climate by 40 percent, according to a Cambridge University report published in September.
The more flights in the air, however, the more complicated the implementation of such a system would be, notes Boyer-Souchet, who hopes that it will be a reality by 2030.
© 2024 AFP
12 Comments
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Desert Tortoise
The article said daytime contrails are not a problem because they are short lived. The concern was contrails at night that remain for hours and could trap heat that otherwise would escape.
1glenn
Man-made, artificial clouds contributing to global warming? While their effect on the atmosphere is not zero, it most likely pales into insignificance compared to emissions of green-house gases such as CO2, nitrous oxide, and methane.
Hercolobus
What about the chem trails?
Jimizo
This keeps coming up.
Well…they are more important than you or I in the grand scheme of things.
They may be elitist, leftist, balanced diet eating, soyboy cucks who aren’t jacked and need to wake up to the conspiracies after watching podcasts but they are more important than you or I.
Still, more zoom than travel should be in order for them.
Moonraker
I am not a climate change denier by any means but there is a glaring omission here: how much do contrails during the day reflect heat back into space? Some clouds do and it is the kind of omission the deniers would pounce on to assert an agenda among climate change scientists (perhaps even as far as to implement global communism).
Moonraker
@Desert Tortoise. Well actually it says, "Contrails that stay in the sky for a few minutes are not very worrisome," but that could imply that some stay longer and it is only the ones that stay for a few minutes that are not. In some places in Europe which I am familiar with they hang around for much longer than a few minutes. Even if the nighttime contrails are an issue perhaps it could be balanced against a possible good daytime ones do in reflecting heat. It says that nighttime ones only "maybe last a little longer" so there might be a significant benefit of daytime ones proportional to the deleterious effects of these also short-lived nighttime ones. If not, at least a statement that scientists have either not measured it or are sure there is no beneficial effect would have been welcome. I don't actually know, but you might be able to discern from my post that it is not really about the good or bad of contrails; it is about the article itself. If I can think of an omission then the deniers will be all over it for reasons other than actual science.
Bad Haircut
So, are you going to fly from now on, since by your logic doing so would be irresponsible given the environmental damage you believe flying is responsible for?
TaiwanIsNotChina
I think people should stop worrying about what others are doing and do what they can to limit carbon emissions.
Bad Haircut
I bet this "revelation" won't stop the rule makers from flying, coz they're important and stuff.
But if we want to fly home for a trip or to some lovely leisure location? Well, we're contributing to climate change and need to be penalised for being so naughty.
kurisupisu
I limit my flying to attain a number of different goals.
I no longer fly just for trivial leisure activities.
virusrex
You mean you are surprised the people that are protected by their power and money from the worst consequences of climate change will still act irresponsibly?
If something can be proved scientifically then it remains true, even if irresponsible people act in a way that makes things worse (for the rest). Just because someone chooses to smoke (and expose others to second hand smoke risks) that would not make the health problems disappear.
virusrex
Still an imaginary thing from scientifically illiterate propaganda groups the same as giant hurricane producing lasers and earthquake directing machines. Safe to ignore this and focus on real problems.