The “fasten your seatbelt” sign may soon be a permanently-lit feature on aeroplanes. Scientists think that global warming is affecting the earth’s atmosphere and, in turn, making flights bumpier.

Turbulence can be a terrifying experience. In August, a transatlantic flight to London Heathrow had to make an emergency stop in Shannon, Ireland, after encountering severe turbulence that left 12 passengers and flight attendants needing hospital treatment for injuries. One passenger described how people hit the ceiling of the aircraft, and it felt like they were going to crash.

“We reached the mid-Atlantic when, suddenly, there was a sensation of the plane slamming into mid-air. It felt like it was made of paper and hitting a solid object,” he told the BBC.

What causes turbulence?

According to the Federal Aviation Administration, turbulence is air movement created by atmospheric pressure, jet streams, air around mountains, cold or warm weather fronts or thunderstorms. “Clear air turbulence” is turbulence that can’t be seen because the sky appears clear. The problem is that clear turbulence can be difficult for pilots or the on-board equipment to detect.

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And it could become more common. Scientists at the University of Reading say that turbulence is on the rise, and it’s due to global warming.

This is because climate change is going to make jet streams – ribbons of very strong winds which move weather systems around the globe – stronger.

Image: University of Reading

“Clear-air turbulence is linked to atmospheric jet streams, which are projected to be strengthened by anthropogenic climate change,” says the study.

“When we think of global warming we’re usually thinking about the fact that it’s getting warmer at ground level, but in fact the temperatures are changing higher up in the atmosphere, including where planes fly at 35,000ft,” Paul Williams, one of the authors of the study, told the Telegraph newspaper.

“As the climate changes the odds of encountering turbulence on your flight are increasing.”

It’s a view shared by the International Civil Aviation Organization (ICAO) in its Environmental Report 2016, which adds that global warming will also affect routes, journey times and fuel consumption of airlines.

The impact of aviation on climate change

Aviation is the most emissions-intensive form of transport, and also the fastest-growing source of emissions in the transport sector.

Sustainable fuels make up only 3% of transport fuels, but this figure must grow to 10% by 2030 to meet economic growth and help keep global warming below 2°C, says the ICAO report.

The ICAO wants to see a 2% fuel efficiency improvement annually, and carbon neutral growth from 2020.