Climate change fuels increased air turbulence

Seasoned air travellers are accustomed to the seatbelt sign turning on with a chime and accompanied by an announcement by the captain or the flight attendants asking them to keep the seatbelt on as turbulence is expected. In 99.99% cases, the seatbelt sign would be switched off after a few minutes. But in the rarest of rare instances, severe flight turbulence can strike, as it happened on May 21 when one passenger died and more than 20 people were injured on an extremely bumpy Singapore Airlines flight travelling from London to its home country. Experts say it’s the kind of incident that could become more common as climate change and global warming accelerate.Between 2009 and 2023, there were 185 serious injuries on 162 global flights involving turbulence for scheduled air carriers (large US-based airlines, regional air carriers and cargo carriers with specific Federal Aviation Administration certificates), according to the US National Transportation Safety Board. Climate change could make severe turbulence a bigger problem in the future. Last year, a study published in Geophysical Research Letters found that turbulence in some parts of the world may already be on the rise, Bloomberg reported.When an aircraft is flying, air is flowing over the wings, causing them to lift and enabling flight, said Larry Cornman, a physicist studying turbulence with the NSF National Center for Atmospheric Research. Turbulence occurs when that airflow is disrupted — essentially, when there’s variation in the wind field around an aircraft. The result, Cornman says, is the plane may "bounce up or down, pitch or roll or move in any direction.” There is also ‘clear-air turbulence,’ which is tricky as it is not associated with visible weather patterns, and pilots can’t easily see it.Many things can cause turbulence. "Jet stream turbulence is a fairly common one,” Cornman said. Jet streams are large rivers of air moving rapidly through the atmosphere, typically at higher altitudes. Because the air is moving so quickly, there can be location variations that get amplified and turned into waves. Sometimes they break, like a wave on the beach. This large source of energy triggers turbulence. Similarly, air flowing over mountains can generate waves that propagate up into the atmosphere and break, triggering turbulence. Thunderstorms also cause turbulence. While pinpointing the exact relationship between climate change and any given turbulent flight is impossible, a series of studies published over the past decade suggest that climate change stands to make turbulence worse in the future, if it isn’t already.In 2017, a study in Advances in Atmospheric Sciences used climate model simulations to investigate trans-Atlantic wintertime clear-air turbulence as it relates to climate change. Researchers from the UK’s University of Reading found that a doubling of carbon dioxide concentrations in the atmosphere could cause light turbulence to increase by roughly 59%, moderate turbulence by 4% and moderate-to-severe turbulence by 127%.A separate 2019 study in Nature found that climate change is already adding to turbulence via an increase in what’s known as the vertical shear in the North Atlantic jet stream. And last year, a study in Geophysical Research Letters used 21 different turbulence calculations to determine whether turbulence got worse between 1979 and 2020. The researchers found "clear evidence” of large clear-air turbulence increases in certain parts of the world."We recently discovered that severe clear-air turbulence in the North Atlantic has increased by 55% since 1979,” said Paul Williams, a professor of atmospheric science at the University of Reading who wrote the 2017 study and co-authored the 2019 and 2023 research."Our latest future projections indicate a doubling or tripling of severe turbulence in the jet streams in the coming decades,” Williams said, "if the climate continues to change as we expect.” In short, passengers should keep their seatbelt on for as much of the flight as possible.