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Turbulence strong enough to bounce unbuckled passengers around an aircraft cabin could become three times more common as carbon dioxide levels in the atmosphere rise, experts predict.

Sudden up and down movements as an aircraft travels through rough air are part of the normal experience of flying.

But occasionally passengers and flight crew are subjected to white-knuckle levels of turbulence with the potential to cause serious injury, especially when it occurs unexpectedly in cloudless “clear air”.


Not in the clear

The effects of climate change on jet streams – high altitude channels of fast-flowing air – are expected to make such roller-coaster flights far more frequent, the new findings suggest.

Using supercomputer simulations, scientists found that a doubling of carbon dioxide (CO2) levels in the atmosphere would increase the average amount of severe clear air turbulence at 11 kilometres by 149 per cent.

As a result, hazardous turbulence on commercial flights could become twice or even three times more common than it is today.

Atmospheric CO2 could be twice what it was in pre-industrial times by the middle of the century if current trends continue.

“Our new study paints the most detailed picture yet of how aircraft turbulence will respond to climate change,” says Paul Williams, from the University of Reading, who led the research.

“For most passengers, light turbulence is nothing more than an annoying inconvenience that reduces their comfort levels, but for nervous fliers even light turbulence can be distressing,” he says. “However, even the most seasoned frequent fliers may be alarmed at the prospect of a 149 per cent increase in severe turbulence, which frequently hospitalises air travellers and flight attendants around the world.”

Commercial passenger jets on long-haul flights routinely cruise at altitudes of 9-12km.

Injuries

The scientists looked at the impact of stronger “wind shear”, a major cause of turbulence, on winter-time transatlantic flights. Wind shear refers to vertical or horizontal changes in wind speed and/or direction over a short distance.

The study predicts that doubling CO2 levels will increase light turbulence by 59 per cent, light-to-moderate turbulence by 75 per cent, moderate turbulence by 94 per cent, moderate-to-severe turbulence by 127 per cent, and severe turbulence by 149 per cent.

Typically, a patch of turbulence lasts about five minutes of flight time, covers a distance of 60 kilometres and is one kilometre thick.

Conservative estimates suggest that each year, an average 790 episodes of turbulence result in 55 serious injuries to flight attendants and passengers travelling with scheduled US carriers, the researchers say.

The same turbulent flights are thought to cause 687 minor injuries to flight attendants and 120 to passengers.

But the actual injury rate is likely to be much higher because many incidents are not reported. Other estimates suggest there could be 5,000 encounters with “severe” turbulence each year.

As well as causing injury, in-flight turbulence can damage aircraft, the scientists say.

On December 9, 1992, extreme clear-air turbulence tore six metres off the left wing of a jet flying over Colorado, US, causing the plane to lose one of its four engines. “An intensification of clear-air turbulence could have important consequences for aviation,” the researchers say.

Journal reference: Advances in Atmospheric Sciences, DOI: 10.1007/s00376-017-6268-2