Tens of thousands of aircrafts face severe turbulence each year, with an estimated cost to the global aviation sector of up to $1 billion from structural damage to airplanes, flight delays, and costs of injuries. Now, a team of researchers led by the University of Reading in the UK has found that climate change could be the main culprit behind this phenomenon, leading to more turbulence during flights, which drive up maintenance costs and increase the risks for both passengers and crews.
While some aircraft turbulence occurs in well-defined places, such as within the vicinity of convection storms or over mountain ranges, a particular type called “clear-air turbulence” (CAT) is caused when bodies of air moving at different speeds meet. Unlike the other types of turbulence, CAT is highly difficult to observe and forecast.
“The main problem [with CAT] is that you can’t see it,” said Ramalingam Saravanan, a professor of Atmospheric Sciences at Texas A&M University, who was not involved in the current study.
“The best way I think pilots know about it is when some other pilot has flown through it and radios back, letting them know its location. You can try to predict it statistically, but you can’t predict it by individual case because it is a random process, and the air looks clear and harmless – hence the name.”
The experts analyzed clear-air turbulence trends globally during 1979 and 2020 by using a dataset called ERA5. “This dataset contains information about the past atmosphere – e.g. temperature, wind speed – that we have used as the basis for this study,” said lead author Mark Prosser, a doctoral student in Meteorology at Reading. “Although information automatically recorded from aircraft do go into this dataset, other observations – such as those from satellites and weather balloons – do so too.”
The analysis revealed that the skies aircrafts fly through have becoming increasingly “bumpier” during the past four decades in various regions of the world.
For instance, over the North Atlantic – one of the busiest flight routes in the world – the total annual duration of severe turbulence has increased by 55 percent, from 17.7 hours in 1979 to 27.4 hours in 2020, while moderate turbulence has risen by 37 percent (from 70 to 96.1 hours) and light turbulence by 17 percent (from 466.5 to 546.8 hours).
The experts argue that these increases are consistent with the effects of climate change, with warmer air caused by rises in greenhouse gas emissions increasing windshear in the jet streams – the narrow currents of fast-moving air that planes fly along to get a speed boost – and consequently strengthening clear-air turbulence in the North Atlantic and other busy flight routes over the US, Europe, the Middle East, and the South Atlantic.
“Turbulence makes flights bumpy and can occasionally be dangerous. Airlines will need to start thinking about how they will manage the increased turbulence, as it costs the industry $150–500m annually in the USA alone. Every additional minute spent travelling through turbulence increases wear-and-tear on the aircraft, as well as the risk of injuries to passengers and flight attendants,” Prosser said.
“Following a decade of research showing that climate change will increase clear-air turbulence in the future, we now have evidence suggesting that the increase has already begun. We should be investing in improved turbulence forecasting and detection systems, to prevent the rougher air from translating into bumpier flights in the coming decades,” concluded co-author Paul Williams, a professor of Atmospheric Science at Reading.
The study is published in the journal Geophysical Research Letters.
Airplane turbulence refers to irregular motion of an aircraft, caused by changes in air pressure or air currents, particularly when the plane is flying through a weather system. It’s one of the common situations that can occur during a flight, and while it might feel unsettling or uncomfortable, it’s usually not a cause for concern. There are several types of turbulence:
This is the most common type of turbulence. It’s caused by fast moving air near the jet stream (usually at high altitudes) and is often not detectable by weather radar, which can make it difficult to avoid. Despite the abrupt jolts, CAT is generally not dangerous, though passengers are still advised to keep their seatbelts fastened when seated.
This is caused by hot air rising and cold air descending. This often happens on sunny days when the sun heats the earth’s surface, causing pockets of warm air to rise. This is most common during the summer and in tropical areas.
This type of turbulence is caused by the wind blowing over rough terrain or buildings, creating eddies in the air. These eddies can cause turbulence when an aircraft flies through them.
This is caused by the spinning vortices that form at the tips of an aircraft’s wings. These vortices can persist in the air and cause turbulence for aircraft flying behind. Air traffic control keeps aircraft separated by specific distances to prevent encounters with wake turbulence.
Although turbulence can be uncomfortable, modern aircraft are built to withstand even severe turbulence. The main danger with turbulence is not to the aircraft itself, but to unsecured objects and people inside the cabin.
Pilots and air traffic control use weather radar and other information to try and avoid turbulent areas when possible. Despite these efforts, turbulence is sometimes unavoidable, but again, it’s usually not a threat to the safety of the flight.