Why strong hurricanes are becoming more frequent
Published: Thursday, Oct 10th 2024, 17:30
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Does a hurricane now hit the USA every two weeks? Probably not. But strong hurricanes have indeed become more frequent there. Their effects can be felt as far away as Switzerland.
People in the US state of Florida barely had time to clean up and breathe a sigh of relief. There were only two weeks between hurricanes "Helene" and "Milton". One thing is clear: climate change is making such violent hurricanes more frequent.
WHAT EXACTLY DOES THE CLIMATE HAVE TO DO WITH HURRICANES?
Climate change is not only causing air temperatures to rise, but also those of the water in the oceans. When "Helene" formed, temperatures in the Gulf of Mexico were around two degrees Celsius higher than before the start of industrialization. The warmth gives hurricanes more energy and makes them more dangerous.
The result: not necessarily more hurricanes - but stronger ones. "A two degree higher water temperature leads to a hurricane with a wind speed that is 80 kilometers per hour higher," said ARD meteorologist Karsten Schwanke recently.
Researchers have even suggested expanding the hurricane scale because there are now storms with wind speeds well above those of other force 5 storms, i.e. the highest category to date. They reach more than 300 kilometers per hour.
ARE THERE OTHER EFFECTS OF CLIMATE CHANGE?
Warmer air can absorb more moisture. This means that hurricanes today often bring more rain and therefore more flooding than in the past - further increasing their destructive power. In a quick analysis, the World Weather Attribution scientists' initiative calculated that "Helene" brought around ten percent more precipitation than if the storm had formed without climate change.
The higher humidity also has another effect: according to a study, hurricanes weaken much more slowly over land than they used to. Whereas in the 1960s they still had 50 percent of their intensity after one day on land, this figure has now risen to 75 percent.
IS THE RAPID SUCCESSION OF "HELENE" AND "MILTON" RELATED TO THE CLIMATE?
"This is a coincidence," said climate researcher Mojib Latif from the GEOMAR Helmholtz Center for Ocean Research Kiel recently on Deutschlandfunk radio. Individual weather phenomena such as hurricanes can never be accurately predicted. But the probability of such storms has generally increased: "The number of severe hurricanes from category 2 upwards has increased significantly."
WHY DOESN'T SWITZERLAND ACTUALLY GET HIT BY HURRICANES?
Because they are tropical cyclones. They therefore need warm ocean water. The Atlantic off Europe is simply too cool for them to form. However, the foothills of the cyclones can already reach Europe - like "Kirk", which arrived in Switzerland on Wednesday as an autumn low and brought heavy rain. The head of climate monitoring at the World Meteorological Organization (WMO), Omar Baddou, explained last year that such heavy rain events would become more frequent in Europe as the North Atlantic warms up.
WHERE IN THE WORLD DO HURRICANES OCCUR?
In the Atlantic and the north-east Pacific. However, such tropical cyclones, which reach at least hurricane force, also form elsewhere. They just have a different name there: typhoon in the Northwest Pacific and cyclone in the Indian Ocean and Southwest Pacific.
According to the US space agency NASA, the most hurricanes since 1985 have occurred in the Pacific - where the warm water areas are the largest. Interestingly, there are no cyclones directly at the equator because the Earth's rotation also plays a role in their formation. According to the German weather service, a cyclone can only form at a distance of five to eight degrees from the equator - this is when the storm clouds start to rotate.
©Keystone/SDA
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