In the Southern Hemisphere, its storms are much stronger than here. We now know why

Sailors have known it for centuries: the most terrible storms await them in the Southern Hemisphere. Now scientists understand why.

In the logs of ancient ships, you can already read how violent the sea can go to hell in the southern part of the globe. “The waves were so high, they threatened to overwhelm the ship again and again,” a passenger wrote as early as 1849 when he sailed around South America. Several years later, satellite data confirmed navigators’ hunch: Storms are indeed stronger in the Southern Hemisphere, 24 percent stronger to be exact. But no one understood why.

Climatologists University of Chicago He has now come up with a concrete explanation for this phenomenon for the first time. There are two comets: the circulation of the oceans and the great mountains of the northern hemisphere. Moreover, the disputes between the North and the South have increased since the 1980s.

The unknown south
For a long time we didn’t know much about the weather in the southern hemisphere. Most observations of the weather have been on land, and the southern hemisphere has a lot of water. But the advent of satellite measurements in the 1980s allowed us to see just how severe the differences could be. The Southern Hemisphere has a stronger jet stream and more extreme weather conditions.

There was no clear explanation for this variance, so the researchers decided to list all forms of evidence, from observations and hypotheses to computer simulations of the climate. “You can’t put earth in a jar,” said lead researcher Tiffany Shaw. “So we instead used climate models and ran experiments to test our hypotheses.”

no mountains
The researchers always removed one variable from the model to see what effect this would have on the strength and number of storms in the Southern Hemisphere. First, they looked at topographical factors: large mountain ridges disrupt airflow in a way that storms shrink, and there are many mountains in the northern hemisphere. In fact, when scientists flattened every mountain on Earth, half of the difference in storm surge between the two parts of the globe disappeared.

The other half must be explained by the circulation of the ocean. Water moves over the Earth like a very slow but powerful conveyor belt: it sinks in the Arctic, travels across the ocean floor, then rises again in Antarctica, then flows almost to the surface, generating energy. This creates an energy difference between the northern and southern hemispheres. When the scientists eliminated this factor as well, the other half of the difference in storm strength disappeared.

More and more storms
Oddly enough, the researchers discovered something else: In recent decades, the difference in storm surge between the two hemispheres has increased. This is mainly because the Southern Hemisphere is becoming more windy, while the Northern Hemisphere is becoming more and more windy. This has to do with changes in ocean currents. They occurred in both hemispheres, but the effect was canceled out in the northern hemisphere because more sunlight was absorbed by the loss of ice and sea ice.

The researchers’ findings are in line with the conclusions of the Intergovernmental Panel on Climate Change. The UN climate panel also expects more storms in the southern hemisphere and no major changes in the north.

unknown future
In a future as Earth’s temperature rises and extreme weather events become more frequent, it is important to understand the physical mechanisms behind climate and the response to human-caused changes. It is critical to be able to predict what will happen if climate change accelerates. “Through this research, we increase confidence in climate models and help the world better prepare for the impacts of climate change,” Xu said. “A major topic has been whether models are now giving us the right information so that we can trust them when they are predicting the future. The stakes are high and it’s important to get the right answer for the right reason.”