Fasten your seatbelts – even tighter.

White-knuckle turbulence powerful enough to seriously injure unbuckled passengers in airplanes could become much more common because of global warming, a new study found.

“Anthropogenic climate change is expected to strengthen the vertical wind shears at aircraft cruising altitudes within the atmospheric jet streams,” an abstract of the study said, referring to environmental conditions affected by human activity.

Researchers at the University of Reading in England used supercomputer simulations to analyze transatlantic clear-air (in cloudless conditions) turbulence during the winter at around 39,000 feet if the atmosphere contained twice as much carbon dioxide.

Commercial airliners normally cruise at altitudes of between 30,000 to 40,000 feet. Wind shear refers to the difference in wind speed and/or direction over a relatively short distance.

The average amount of light turbulence would rise by 59 percent, light-to-moderate turbulence would increase by 75 percent and moderate by 94 percent, the study found.

At the opposite end of the scale, moderate-to-severe turbulence would increase by 127 percent, while severe turbulence would increase by 149 percent.

“These results suggest that the prevalence of transatlantic wintertime clear-air turbulence will increase significantly in all aviation-relevant strength categories as the climate changes,” according to the study.

Atmospheric carbon dioxide levels could double those from the pre-industrial era by the middle of the century.

“Our new study paints the most detailed picture yet of how aircraft turbulence will respond to climate change,” lead researcher Paul Williams said in a statement.

“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,” Williams added.

“However, even the most seasoned frequent fliers may be alarmed at the prospect of a 149% increase in severe turbulence, which frequently hospitalizes air travelers and flight attendants around the world.”

According to conservative estimates, there are 790 turbulence incidents each year among US carriers – resulting in 55 serious injuries to flight attendants and passengers, the study said.

But the actual numbers are likely to be much higher because many incidents are not reported. Other estimates indicate there could be 5,000 encounters with “severe-or-greater” turbulence each year.

For the one in four Americans who are afraid of flying, even minor bumps could be nerve-racking.

But like an earthquake, turbulence is rated on a scale: One is “light” and may be imperceptible, three is “moderate,” or enough to jostle a drink, five is “severe,” and seven is “extreme.”

“Anything above five is by definition stronger than gravity,” Williams said. “What that means is that anything that’s not strapped in will potentially be projected around inside the plane. That would include passengers.”

The study was published in the journal Advances in Atmospheric Sciences.