Technology & Science

Climate change may make for more turbulent flights: study

A new study suggests that an increase in carbon dioxide concentrations in our atmosphere could cause changes in the jet stream over the North Atlantic flight corridor, leading to a spike in air turbulence.

Flight turbulence could increase significantly under climate change

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 2:28

Heads up frequent fliers, nervous fliers and everyone in between: climate change could make air travel a whole lot bumpier.

A new study conducted by atmospheric scientist Paul Williams, of the University of Reading in the United Kingdom, suggests that an increase in carbon dioxide concentrations in our atmosphere could cause changes in the jet stream over the North Atlantic flight corridor, leading to a spike in air turbulence.

In fact, according to the study, by the middle of the century, the volume of airspace experiencing light turbulence could increase by about 59 per cent and severe turbulence would increase by 149 per cent. 

Increased CO2 could make for bumpier flights, a new study suggests. (Mike Hillman/CBC News)

The impacts of climate change on the aviation industry is a fairly new field of research, but studies are steadily accumulating. This latest paper actually builds on a 2013 study in the journal Nature Climate Change that found an increase in moderate to severe turbulence in the North Atlantic as a result of climate change. 

Williams used the same set of conditions and models but extended the research to investigate the effects on all ranges of turbulence, from light to severe. The study also quantifies by how much different kinds of turbulence will increase.

A warmer, bumpier forecast

Clear-air turbulence — the kind that happens without the presence of clouds — is the result of wind shear, a change in wind speed and/or direction over a relatively short distance in the atmosphere. That rapid change in airflow is what can lead to bumpy conditions.

Pilots and air traffic control bodies do their best to avoid turbulence by studying the weather patterns before each flight. (John Fraser/CBC)

Although many other factors can lead to turbulence, previous work on the subject has shown that the jet stream contains about three times more clear-air turbulence than the rest of the atmosphere. The jet stream  — that narrow band of fast-moving air in the upper atmosphere — is driven by the collision of air masses with very different temperatures. 

The jet stream is also where commercial airlines take advantage of that fast-moving air when travelling from west to east, saving time and fuel. 

Some research has already begun to detect changes in large-scale atmospheric currents. One of those projected changes may be an increase in the wind shear at altitudes of 9,000 to 12,000 metres (30,000 to 40,000 feet). It's at these heights that the air above the tropics is warming faster than the air above the Arctic, resulting in an increase in temperature difference that drives wind shear. 

Williams's work imagines a scenario where CO2 concentrations are twice the pre-industrial concentrations — an outlook that most moderate climate scenarios project for future emissions.

He examined 21 different wind-related characteristics known to be indicators of air turbulence levels, including wind speed and changes in airflow direction (wind shear), and found an increase in turbulence across the spectrum as a result of climate change.

"We find that the temperature patterns and the wind patterns in the high-altitude atmosphere are very tightly coupled together. So if we change the temperature pattern [which is what we are doing with the CO2 emissions], wind patterns are changing as a consequence. Specifically, those high-altitude winds are getting stronger because of climate change, and that's increasing the probability of the instability," Williams told CBC News in an interview. 

Air turbulence can be caused by a number of factors, including heat, jet streams and flying over mountain ranges. (John Fraser/CBC)

It should be noted that even with a 149 per cent increase in severe turbulence, severe turbulence would still be an extremely rare occurrence for passengers. Williams explained that "something like 0.1 per cent of the atmosphere at typical cruising altitudes contains severe turbulence. That sounds small, but given the large number of planes in the sky at any moment, sooner or later one of them is bound to encounter that 0.1 per cent purely by accident. However, even if this figure tripled later this century, which is at the top of the range of projections in our study, it would still be only 0.3 per cent." 

What does this mean for the aviation industry?

Williams also points out that the projected increase in the prevalence of clear-air turbulence does not necessarily imply more in-flight injuries or greater levels of passenger discomfort. In the future, the skill of clear-air turbulence forecasts and in-flight detection may improve, meaning pilots will be better equipped to divert around patches of clear-air turbulence. 

Some aircraft already have automatic responses to the first signs of turbulence to dampen vertical motion, and that technology may also improve.

Williams suggests future work should examine other seasons, flight levels and geographic regions, as well as model resolution and sensitivity.

Paramedics exit an Air Canada plane after 10 passengers were injured in January 2008, when the plane hit turbulence over the Rocky Mountains while en route to Toronto from Victoria. The plane was forced to land in Calgary. (Todd Korol/Reuters)

Williams also adds: "The airlines have a treasure trove of turbulence data to help test our theories and forecasting algorithms, but obtaining access to the data can be difficult. It would be great if the airlines were more open to sharing their turbulence data with atmospheric scientists like me, to help keep flying as pleasant, safe and comfortable as possible."

When CBC asked Transport Canada what they make of the new research, they said: "Transport Canada constantly reviews the latest research to support evidence-based policy decisions. Our experts look forward to reading this paper; thank you for bringing it to our attention." 

About the Author

Johanna Wagstaffe

Senior Meteorologist

Johanna Wagstaffe is a senior meteorologist for CBC, covering weather and science stories, with a background in seismology and earth science. Her weekly segment, Science Smart, answers viewers' science-related questions.