International ozone treaty stops changes in Southern Hemisphere winds

Now, new research in Nature finds that those changes have paused and might even be reversing because of the Montreal Protocol, an international treaty that successfully phased out use of ozone-depleting chemicals.

Not only has the treaty spurred healing of the ozone layer, it's also driving recent changes in Southern Hemisphere air circulation patterns," said lead author Antara Banerjee, a CIRES Visiting Fellow at the University of Colorado Boulder who works in the Chemical Sciences Division of the National Oceanic and Atmospheric Administration (NOAA).

Ultimately, ozone depletion has shifted the midlatitude jet stream and the dry regions at the edge of the tropics toward the South Pole.

In this study, Banerjee and her co-authors have shown that around the year 2000, the circulation of the Southern Hemisphere also stopped expanding polewards--a pause or slight reversal of the earlier trends.

"The challenge in this study was proving our hypothesis that ozone recovery is in fact driving these atmospheric circulation changes and it isn't just a coincidence," Banerjee said.

"Identifying the ozone-driven pause in circulation trends in real-world observations confirms, for the first time, what the scientific ozone community has long predicted from theory," said John Fyfe, a scientist at Environment and Climate Change Canada and one of the paper's co-authors.

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