Are there such things as arctic hurricanes

Hurricanes with full force

If a hurricane hits the American coast with wind speeds of up to 300 kilometers per hour, it causes enormous devastation there. This risk could become even greater as global warming increases. This is the conclusion reached by climatologists who examined the strength of the cyclones over the past fifty years. As they report in the journal "Nature", the hurricanes are less and less weakened as they pass from the open sea to the land area. They found one reason for this in the increased surface temperature of the adjacent sea.

In the late 1960s, hurricanes lost around three quarters of their intensity on the first day of transition from the sea to the land area during the annual hurricane season - from June 1 to November 30. In contrast, the strength of the hurricanes only decreased by around half between 2015 and 2018. This trend has now been shown by the analysis by Lin Li and Pinaki Chakraborty from the Okinawa Institute of Science and Technology, who examined all hurricanes between 1967 and 2018. The researchers also observed the mean surface temperature in the Gulf of Mexico and the Caribbean. In the 2010s, this was around one degree Celsius higher than fifty years earlier.

Using computer simulations, the researchers checked whether these two effects are related. Because the warmer the sea surface, the more water evaporates, which the hurricanes could in turn absorb. The simulations showed that the moisture stored in the cyclone actually increased at higher water temperatures. And the more moisture was stored in a hurricane, the more slowly the strength of the cyclone decreased. In comparison, Li and Chakraborty also simulated cyclones that did not store moisture. These hurricanes were weakened much more strongly when they went ashore - regardless of the water temperature.

The analysis provides strong indications that cyclones in the course of climate change actually lose less intensity on land areas and last longer. As a result, hurricanes can cover longer distances and devastate ever larger areas. Li and Chakraborty warn that regions that have previously been spared by hurricanes could be affected by hurricanes in the future. In further studies, the researchers want to investigate whether the effect can also be observed in other tropical regions.