Climate change
Why strong hurricanes are becoming more common
Shortly before “Milton” made landfall, the hurricane looked like this from a satellite. photo
© Uncredited/National Oceanic and Atmospheric Administration/AP/dpa
Does a hurricane now hit the USA every two weeks? Probably not that. But strong hurricanes have actually become more frequent there. Their effects can be felt as far as Germany.
The people of 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: The Climate change is making such violent hurricanes more common.
What exactly does 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, they were about two degrees Celsius higher in the Gulf of Mexico than before the start of industrialization. The heat causes hurricanes to gain more energy and become more dangerous.
The result: Not necessarily more hurricanes – but stronger ones. “A water temperature that is two degrees higher in a hurricane leads to a wind speed that is 80 kilometers per hour higher,” said ARD meteorologist Karsten Schwanke in the “Tagesthemen”.
Researchers have even suggested expanding the hurricane scale because there are now storms that have wind speeds well above the wind speeds of other force 5 storms, i.e. the highest category to date. They reach more than 300 kilometers per hour.
Are there any other effects of climate change?
Warmer air can hold more moisture. This means that hurricanes today often bring more rain and therefore floods earlier – thus increasing their destructive power even further. The World Weather Attribution scientific initiative calculated in a quick analysis that “Helene” brought about ten percent more precipitation than if the storm had formed without climate change.
The higher humidity has another effect: According to a study, hurricanes weaken over land much more slowly than before. While in the 1960s they were at 50 percent of their intensity after a day on land, they are now at 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 on Deutschlandfunk. Individual weather phenomena such as hurricanes can never be predicted precisely. But the probability of such storms has generally increased: “The violent hurricanes from category 2 onwards have increased significantly.”
Why isn’t Germany actually hit by hurricanes?
Because these are tropical cyclones. So you need warm ocean water, namely 26 degrees Celsius up to a depth of around 50 meters, according to the German Weather Service (DWD). The Atlantic off Europe is simply too cool for this to occur.
However, the tails of the hurricanes can reach Europe – just like “Kirk”, which arrived in Germany on Wednesday as an autumn low and brought heavy rain. Such heavy rain events would become more common in Europe as the North Atlantic warmed, the head of climate monitoring at the World Weather Organization (WMO), Omar Baddou, explained last year.
Where in the world do hurricanes form?
In the Atlantic and the northeast Pacific. However, tropical cyclones of at least hurricane strength also form elsewhere. There they are just called differently: 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 largest. Interestingly, there are no hurricanes directly at the equator because the Earth’s rotation also plays a role in their formation. According to the DWD, a cyclone can only form at a distance of five to eight degrees from the equator – then the storm clouds start to rotate.
Study in “Nature” on weakening hurricanes over land Education server Hamburg: Tropical cyclones in Europe? DWD on tropical cyclones Education server Hamburg: Tropical cyclones and global warming Rapid study on “Helene” Saffir-Simpson hurricane scale Interview with Mojib Latif on Deutschlandfunk Study on expanding the hurricane scale