What On Earth24:22Bumpy flight? Climate change may be to blame
When Luke Wheeldon stepped onto Air Canada Flight AC33 in July of 2019, he was exhausted.
He was heading home to Australia after his band, Hurricane Fall, played a music festival in P.E.I. “Keen for a sleep,” he took his seat near the back of the plane near midnight, did up his seat belt and hoped no one would disturb him.
Further up the plane was Linda Woodhouse. She and her partner were on their way to Perth, Australia, where Woodhouse had accepted a professor job at the university.
It would be 15 hours from Vancouver to Sydney, and the plane was quite full: old, young, parents with small children, mothers breastfeeding their babies. But Woodhouse was used to flying and calmly buckled up.
Seven hours in, the smell of breakfast spread through the plane, and some passengers were waking up. Wheeldon’s bandmate got up to use the bathroom.
“There was no indication of anything,” he recalled. “There was a little rumble, but the seat belt signs weren’t on.”
It was then that Woodhouse remembers a few quick bumps, turbulence that felt “different.”
She reached over to her partner, to make sure her belt was done up. It was.
“Then the plane just dropped,” she said.
“It felt like King Kong just grabbed the plane and shook it,” said Wheeldon. “In front of me, like 50 odd people flew into the roof.”
The sounds of bodies hitting the baggage compartment was very disturbing, says Woodhouse. She says she thought the plane was going down.
The older lady in front of her wasn’t wearing her seatbelt and flew up and hit her head on the ceiling. Flight attendants were thrown into the air.
Wheeldon’s bandmate next to him, having just returned from the washroom and not buckled in yet, was tossed up into the luggage compartment above. It was later found he’d broken his neck in six places, according to Wheeldon.
But then, the plane “shook a little bit more, and then it was over,” said Wheeldon.
Those 10 to 15 seconds that left 37 people injured was caused by a phenomenon known as severe clear-air turbulence, which is happening more often — and forecast to get even worse due to climate change.
The rise has researchers investigating how to better predict clear-air turbulence, and looking to the physics of birds to make this chaotic force less dangerous.
Why is it increasing?
Paul Williams, the head of the Meteorology Department at the University of Reading in the U.K., has always been fascinated by turbulence. He notices it everywhere.
“Not just on flights, but everywhere around us in your cup of coffee, in the bathtub, it’s in the ocean, it’s in the atmosphere.”
His research exposed this link between climate change and increased clear-air turbulence.
Unlike other types of turbulence, caused by flying through a storm or near a large mountain, you can be flying through “clear blue skies” and still hit it, says Williams.
It’s specifically this invisible clear-air turbulence that is becoming more prevalent as the planet warms.
“It all boils down to what is climate change doing to temperature patterns in the atmosphere, and specifically the upper atmosphere between 35,000 and 40,000 feet,” or 10 to 12 km above sea level.
The reason is that at that level, the jet stream — a current of very strong winds where planes like to fly — is warming faster near the equator than near the poles. (At ground level, the opposite is true, with the Arctic warming faster than elsewhere.)
This collision of that hotter air with cooler air at the edge of the jet stream is creating something called wind shear, which increases with height. “So the higher up you go in the atmosphere, the windier it gets,” said Williams.
It’s that “windier” jet stream that is creating clear-air turbulence.
A lot windier. Williams has found that today over the North Atlantic, there’s 55 per cent more severe clear-air turbulence than there was back in 1979. Over North America he says there’s 41 per cent more than in 1979.
Hard to predict
Because clear-air turbulence can’t be seen or detected with onboard equipment, it’s hard for pilots to avoid — but scientists are working on better predictions.
That’s been difficult, because the eddies that cause turbulence for planes happen at a scale that was too small for the available computer models to capture.
Williams says forecasting algorithms have improved because of better satellite observations and better understanding of how turbulence is made.
“When I first started out thinking about turbulence, the forecasts were about 60 per cent accurate…. Over my career, over the past two and a half decades, that figure has increased [to] 75 or perhaps even 80 per cent.”
But, the problem is also forecast to get much worse. If action isn’t taken to cut emissions, severe clear-air turbulence is expected to double over North America, the North Pacific and Europe.
Severe turbulence, like that on an American Airlines flight that left 10 people needing hospital treatment, is becoming more frequent due to factors caused by climate change, a recent study suggests
So far, turbulence is growing faster than the ability to predict it.
Looking to birds
As a little girl, Aimy Wissa loved airplanes, and knew she wanted to study them.
She’s now an associate professor of aerospace and mechanical engineering at Princeton University, and that love of flight has taken a new form.
“[In grad school] I was just reading about birds … technical papers, and I just fell in love.” At her current position as the head of Princeton’s bio-inspired morphology lab, those two loves combine.
The lab aims to learn from nature to make mechanical systems work better. They look at flying fish to see what they can teach them about making a machine that can both swim and fly. Or, what an insect can show engineers about how to make a small machine super powerful.
And of course, what can birds teach us about how to build planes?
In 2024 she and her team published a peer-reviewed study with some promising results from research into what birds can teach us about how to make airplanes more stable in adverse flying conditions, like unexpected turbulence. The goal is to expand the plane’s flight envelope, which is basically the safe operating limits for a plane.
“Think of an eagle, think about all the things that an eagle has to do. It can fly in a cluttered environment … it can come close to the water and pick a fish that’s almost half of its weight, you know, crazy things like that.”
Birds have multiple layers of feathers on their wings, Wissa and her team looked at a type called “covert feathers” which are layered overtop of the rest of the feathers on a wing.
They simulated these feathers by attaching a plastic flap on the wing of a small remote control airplane. After testing the best place for this flap in a wind tunnel at Princeton they took the plane outside.
They forced the plane to stall, basically making it lose its ability to create lift which is what allows a plane to fly.
They found this small flap not only made it less likely for the plane to stall, but it also helped the pilot navigate during a period of stall.
“So I think it’s promising,” said Wissa. She said though the flaps are not ready for airplanes, the discovery that they might support more stable flights is “very exciting.”
This GoPro video from Princeton University’s bio-inspired adaptive morphology lab shows testing of a flap designed to make airplanes more stable in unexpected turbulence.
What can flyers do?
Linda Woodhouse and Luke Wheeldon have flown many times since that terrifying event in 2019 on Air Canada Flight AC33.
But for Woodhouse, it’s the moments before the flight that have forever changed.
“I get on a flight, now you stop and think, is this the last one? And I’ve never ever been like that before […] you pause and say, have I told my family, have I told my mentors, have I told my friends how much I care about them?”
There is another mental check she does every time she boards a flight.
“I look around at how many people take off their seatbelt to fall asleep, et cetera, and I have to stop myself from going over to say, you really ought to be flying with your seatbelt.”
The data backs that up, says Paul Williams.
“If you look at the injuries, there’s almost no injuries amongst passengers who were seatbelted. It’s virtually a guarantee of safety. It’s crazy not to keep your seatbelt fastened.”
“Just wear your bloody seatbelt,” said Luke Wheeldon.
