Airplane passengers are in for an increasingly bumpy ride according to a study released today in the journal Advances in Atmospheric Sciences. Climate change is altering the jet stream, making severe turbulence more likely. The study builds on earlier work which found that climate change would lead to bumpier airplane rides. What makes the new research unique is that it quantifies how much different kinds of turbulence will increase—59 percent in the case of light turbulence, a 94 percent increase in moderate turbulence, and 149 percent increase in severe turbulence.

For the one in four Americans who are afraid of flying, any jostling could be considered severe. But like an earthquake, turbulence is rated on a scale. One is light—gentle enough so passengers may not notice it—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," says study autho Paul Williams, an atmospheric scientist at the University of Reading in the United Kingdom. "What that means is that anything that's not strapped in will potentially be projected around inside the plane. That would include passengers."