The air over which planes fly is rougher today than it was 40 years ago, scientists have found, suggesting turbulence has increased due to changes in weather.

This is according to new research from the University of Reading turbulence in clear air _what is invisible and dangerous to aircraft_ has increased in different parts of the world.

At a typical point over the North Atlantic, one of the busiest flight paths in the world, the total annual duration of severe turbulence increased by 55%, from 17.7 hours in 1979 to 27.4 hours in 2020, the study found.

Moderate turbulence increased 37% from 70.0 to 96.1 hours and light turbulence increased by 17% from 466.5 to 546.8 hours.

The team behind the study, which is published in Geophysical Survey Letterssays the increases are consistent with the effects of climate change.

Warmer air from CO2 emissions increases wind shear in jet streams, amplifying clear air turbulence in the North Atlantic and around the world.

“Turbulence makes flights bumpy and can be dangerous at times. Airlines will have to start thinking about how to handle the increased turbulence, as it costs the industry $150-500 million a year in the US alone,” said researcher Mark Prosser.

“Every extra minute we travel through turbulence increases wear and tear on the aircraft, as well as the risk of injury to passengers and flight attendants,” he added.

While the US and the North Atlantic have seen the biggest increases, the new study found that other heavily traveled flight paths over Europe, the Middle East and the South Atlantic they also experienced a significant increase in turbulence.

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Paul Williams, an atmospheric scientist at the University of Reading and co-author of the study, said: “After 10 years of research showing that future climate change will increase turbulence in clear skies, we now have evidence to suggest that the increase has begun”.

The expert believes that it should already be invest in better turbulence detection and prediction systems, to prevent rougher air from translating into bumpier flights for decades to come.