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Climate Change Causing Bigger Cyclones

FILE: People cross a raging river in Blantyre, Malawi, Monday, March 13, 2023. An unrelenting Cyclone Freddy battered southern Africa in Malawi and Mozambique, striking the continent for a second time.

PARIS - Climate change does not make cyclones more frequent but it does render them more intense and destructive, according to climatologists and weather experts.

"The overall number of tropical cyclones per year has not changed globally but climate change has increased the occurrence of the most intense and destructive storms," according to the World Weather Attribution (WWA), a group of climate scientists and climate impact specialists whose goal is to demonstrate reliable links between global heating and certain weather phenomena.

The most violent cyclones - categories three to five on the Saffir-Simpson scale - that cause the most destruction have become more frequent, the WWA said.

Climate change caused by human activity influences tropical cyclones in three major ways - by warming the air, the oceans, and by triggering a rise in sea levels.

"Tropical cyclones are the most extreme rainfall events on the planet," the WWA said in its publication "Reporting Extreme Weather and Climate Change."

Since the atmosphere is warmer, it can hold more water, so when it rains it pours.

"A rise in air temperature of three degrees Celsius can potentially produce a 20-percent increase in the quantity of rain generated by a cyclonic event," said Cloppet.

It is these intense torrential downpours that lead to sometimes fatal floods and mudslides, as was the case of Cyclone Freddy, which killed hundreds of people in Malawi and Mozambique earlier this year.

Climate change is also warming the oceans. This warm water fuels cyclones and gives them their strength.

"Climate change therefore creates the conditions in which more powerful storms can form, intensify rapidly and persist to reach land, while carrying more water," the WWA said.

Scientists also expect to see cyclones in places they have not happened before because global heating is expanding the regions where tropical sea water conditions occur.

"It's as if the tropics were spreading," Cloppet said.

"Areas that aren't really affected now could be hit much harder in future."

The WWA agreed: "As ocean waters warm, it is reasonable to speculate that (tropical) storms will shift further away from the Equator."

"A northward shift in cyclones in the western North Pacific, striking East and Southeast Asia, (is) a direct consequence of climate change," it said.

As a result, they could strike in relatively unprepared locations that have not, in the past, had reason to expect them.