How Pilots and Scientists Are Thinking About the Future of Air Travel
It's not just you—in-flight turbulence really is getting worse. WIRED spoke with pilot Andrea Themely and atmospheric scientist Dr. Paul Williams about why conditions are becoming more severe and how the scientific and commercial aviation communities are approaching the future of air travel.
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00:00 "Attention passengers, please return to your seats and fasten your seatbelts."
00:04 You know what that likely means.
00:06 Turbulence.
00:07 And if you've been getting on a plane recently, it feels like turbulence has been getting a lot worse.
00:12 So what does this mean for the future of travel?
00:16 "In a few decades time, it looks a lot more turbulent with hundreds of percent more severe clear air turbulence in those skies."
00:25 And how are pilots reacting to more and more rough air?
00:28 "So we slow down just a little bit to reach that maneuvering airspeed so that it doesn't get bounced around as much."
00:33 First, we need to understand just exactly what turbulence is.
00:41 "Turbulence is a chaotic, random motion that occurs in all fluids. It's around us all the time. It's in your bathtub, it's in your cup of coffee, and of course it's in the atmosphere."
00:51 There are a bunch of different types of turbulence.
00:54 But in particular, we're going to talk about cat.
00:56 No, not that kind of cat, but clear air turbulence.
01:00 Cat is the particular type of turbulence that is getting worse because of climate change.
01:04 And since it involves clear air in the jet streams, it cannot be detected by radar before a plane is in it.
01:10 "Clear air turbulence is generated by wind shear in the jet stream.
01:14 Anyone who's ever climbed a tall building, for example, the Eiffel Tower, very calm at the bottom, but the higher up you go, the windier it gets.
01:22 And that increase in wind speed with height is what's called wind shear.
01:26 When the wind shear is too strong, the atmosphere simply can't contain that and it breaks down into turbulence as a result."
01:33 There are different levels of turbulence. You have light, moderate, severe, and extreme.
01:38 "Severe turbulence is turbulence in which the up and downward motions of the aircraft will experience vertical accelerations that exceed 1g.
01:48 Around 5,000 aircraft annually encounter severe turbulence in the U.S., causing hundreds of injuries to passengers and flight attendants.
01:58 This severe injury-causing turbulence is rare, but of course, multiply that by all the planes that are in the skies at any given moment, and one of them will encounter that severe turbulence."
02:08 For pilots, turbulence is about maintaining passenger comfort and trying to figure out where turbulence could potentially be and then circumnavigating it.
02:16 "So the forces on an aircraft are lift, weight, thrust, and drag. And air is a fluid. It's keeping it airborne, suspended in flight at all times.
02:25 And turbulence is like a minor disturbance in the middle of it."
02:29 How is climate change making turbulence worse?
02:32 "What satellites can see is the three-dimensional shape and structure of the jet stream. And they've been measuring that for at least four decades.
02:40 There's an amplification of the warming in the tropical parts of the planet, and that effect is increasing the north to south temperature difference across the jet stream.
02:49 And that's driving stronger wind shear in the jet stream, which is generating more clear air turbulence.
02:54 So that's the link from temperatures to wind shear to turbulence."
02:59 This is what turbulence looked like in 1979.
03:02 And this is what turbulence looked like in recent years.
03:05 "We see the same pattern, except that the hot spots are even hotter today. There's a greater likelihood of encountering clear air turbulence in those hot spots.
03:13 50 or 60% more turbulence in some regions."
03:17 And this is what turbulence could look like if global warming continues.
03:21 "What we're looking at here is supercomputer simulations of the atmosphere.
03:25 The simulation on the left is our control simulation, whereas the simulation on the right is one in which we've increased the carbon dioxide to describe what a future real world might look like, with a lot more turbulence in the skies that we fly through.
03:38 What we find is that there's a doubling, or perhaps even a trebling, of the amount of severe clear air turbulence in the atmosphere.
03:46 So the future in a few decades' time looks a lot more turbulent, with hundreds of percent more severe clear air turbulence in those skies."
03:55 And where will those hot spots particularly be?
03:58 "There's 55% more severe turbulence over the North Atlantic than there was in the 1970s, 41% more over the U.S., and similar figures around the world.
04:09 That's the definitive evidence, really, that clear air turbulence has already started to get stronger."
04:14 So what does this mean for air travel, in particular over areas like North America and the North Atlantic?
04:20 "We're certainly projecting a doubling or a trebling in the amount of turbulence in a few decades' time, but that will just mean that we go from 0.1% of the atmosphere having severe turbulence in it to 0.2% or 0.3%,
04:34 and that's certainly not going to mean we're going to have to shut down parts of airspace and say there's too much turbulence.
04:39 I don't think that's on the cards, really. It's just a case of turbulence becoming more frequent and pilots needing to keep even closer tabs than they already do on where the turbulence is and trying to avoid it as best as they can."
04:51 For pilots, this means relying on programs like WSI Pilot Brief and Skypath to plan out flight routes.
04:57 "You're looking at a God's eye view of our route of flight. The various hazards along the way are those big green circles and then the red boxes.
05:04 If you look at the bottom half of the screen, that's a vertical profile. You'll see that toward the end, if it stayed at 33,000 feet, it would encounter that big yellow and orange section of turbulence.
05:14 And that's why in this case, this aircraft has chosen to climb all the way up to 39,000 feet to try to avoid it."
05:19 Pilots also use Skypath, which crowdsources turbulence data from other flights.
05:23 Caution! Turbulence detected!
05:26 "The yellow dots means they're encountering light turbulence along the way. You can see that if you hover over any individual dot, like that orange dot there, it'll show you, you're going to encounter moderate turbulence at flight level 400 or 40,000 feet."
05:41 With this information in mind, pilots can decide to circumnavigate turbulence, for example, by adjusting altitude.
05:48 "Clear air turbulence caused by jet streams tends to be due to a very narrow band of air that's moving very rapidly. That narrow band of air may only be 2,000, 3,000 feet thick. And if that's the case, then you can just climb or descend a couple thousand feet and be out of it right away.
06:03 So when we encounter clear air turbulence, the very first thing we'll do, of course, is turn the seatbelt sign on, make sure we call back to the flight attendants and make sure they're either seated if it's bad enough or that they're checking the passengers are seated if it's not bad enough.
06:15 We'll talk to air traffic control right away. We'll figure out what the planes ahead of us are seeing and if they're doing any better at any other altitude so we can climb or descend immediately."
06:25 And for pilots, this also means going as fast as safely possible to get through turbulence.
06:30 "Most of the time when we're flying through clear air turbulence, we're going to keep the auto flight systems on. Oftentimes, the auto throttles, though, in severe turbulence are recommended to be turned off. And the reason why is because those thrust levers will be chasing around airspeeds pretty rapidly and it's not necessarily good for the engines. It's better just to leave them in one steady place and hope that the airspeed is not chasing itself."
06:51 While pilots are in turbulence, they tend to go at maneuvering airspeed.
06:54 "What that is, is the fastest speed that you can fly, have full deflection of your control surfaces and not structurally damage the aircraft. So we slow down just a little bit to reach that maneuvering airspeed so that it doesn't get bounced around as much and that we can go through at the quickest we can without bouncing around the passengers too much."
07:13 The airlines are constantly changing to adapt to our dynamic and changing air travel environment. So if climate conditions make turbulence worse, then we will continue to evolve and make sure that turbulence procedures are reflected in that, even if that means different procedures to avoid it in the first place.
07:30 "I specialize in turbulence. I study it every day. I have done for 20 years. But even for me, when I fly through turbulence, I feel that energy in my stomach, my heart racing. It just plugs into a very primitive part of our brains that logic can't override. And I tell myself, I understand, you know, this is why I study. I'm perfectly safe. It doesn't help."
07:48 "A tip I heard recently is to order a drink and just put the drink in front of you and watch how still the water surface is in turbulence because the emotions are a lot less severe than you think."
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