For centuries, sailors have known where the most fearsome storms are located: the Southern Hemisphere. “The waves ran mountain-high and threatened to overwhelm [the ship] at every roll,” wrote one passenger on an 1849 voyage rounding the tip of movie review South America.
Decades later, scientists poring over satellite data could finally put numbers behind that experience. The Southern Hemisphere is indeed stormier than the Northern, by about 24%. But no one knew why.
A U.S. National Science Foundation-supported study led by University of Chicago climate scientist Tiffany Shaw lays out the first concrete explanation for this phenomenon. Shaw and colleagues found two major culprits: ocean circulation and large mountain ranges in the Northern Hemisphere. The findings are published in Proceedings of the National Academy of Sciences.
The study also found that this storminess asymmetry has increased since the beginning of the satellite era in the 1980s. The increase was consistent with climate change forecasts.
Once, scientists didn’t know much about weather in the Southern Hemisphere. Most of the ways we observe weather are land-based, and the Southern Hemisphere has much more ocean than the Northern Hemisphere. But with the advent of satellite-based global observing in the 1980s, researchers could quantify how extreme the difference was. The Southern Hemisphere has a stronger jet stream and more intense weather events.
