On a recent flight to Chicago, Allison Levy said she was “white-knuckling” the armrest as the plane rumbled and shook for brief periods of time. Ms. Levy, 47, who lives in Arlington, Va., started to take deep breaths and tried to reassure herself: “It’s like a bumpy road — it’s not a big deal.”But, she added, “if I knew the person next to me, I’d definitely grip their thigh.”Airplane turbulence, which is usually caused by large changes in airflow in the Earth’s upper atmosphere, is generally a minor nuisance. But this year alone, there have been multiple instances of severe turbulence on flights that have led to dozens of passenger injuries. And scientists have warned that we may have bumpier flights in the years ahead because of elevated carbon dioxide emissions that are warming the atmosphere, which can alter the speed and direction of the wind.

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Persons: Allison Levy, Levy, “ Locations: Chicago, Arlington , Va