Now this is being caused by climate change and greenhouse gases. This summer has been particularly hot with record temperatures in many countries and coral bleaching in oceans:
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Last year scientists from Reading University found that severe turbulence, from this clean air phenomenon, had increased 55% between 1979 and 2020 in the North Atlantic.
“They said that warmer air from increasing greenhouse gas emissions was changing the wind speed in the jet stream.
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“Prof Paul Williams, an atmospheric scientist at the University of Reading, who co-authored the study told the BBC last year: "We should be investing in improved turbulence forecasting and detection systems, to prevent the rougher air from translating into bumpier flights in the coming decades."
https://www.bbc.com/news/articles/cv22endle1no
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