Suffered a bumpy plane ride recently? You can blame climate change.

Scientists have long predicted that warmer air will trigger alterations to air currents in the upper atmosphere, known as the jet stream, that will increase turbulence on flights.

Now, Mark Prosser at the University of Reading, UK, and his colleagues have collected evidence that plane rides have indeed become bumpier, with analysis suggesting turbulence has increased significantly around the world over the past four decades.

The study looked at climate data from 1979 to 2020 to assess how atmospheric conditions have influenced the occurrence of clear air turbulence. This describes a patch of turbulent air, invisible to the naked eye, which is caused by colliding bodies of air moving at different speeds.

In the North Atlantic, a region crossed by some of the world’s busiest flight routes, the total annual duration of severe turbulence has jumped 55 per cent, the study found, from 17.7 hours in 1979 to 27.4 hours in 2020. Moderate turbulence increased by 37 per cent, from 70 hours to 96.1 hours, over the same period.

This is down to changes to the jet stream, says Prosser. Warmer air temperatures from higher carbon dioxide concentrations are driving stronger wind shear – vertical or horizontal changes in wind speed or direction or both over a short distance. “That change in shear leads to increased turbulence,” he says.

While the North Atlantic and continental US saw some of the greatest rises in turbulence, flight routes over Europe, the Middle East and the South Atlantic also saw significant increases, the study found. In fact, turbulence is rising more than climate models expected for the current level of global warming, the study suggests.

Turbulence will continue to worsen as the climate changes, Prosser predicts. For airlines, this could mean more wear and tear on planes and higher fuel costs as pilots divert flights to avoid turbulence-prone areas. “This is all lost money for the industry,” says Prosser.

Meanwhile, passengers and crew may have to spend more time strapped in during flights to reduce the risk of injury. But Prosser says there is little reason to be “overly concerned”. “Fatalites on commerical aircraft from turbulence are almost unheard of,” he says.