As rising temperatures melt ice caps and cause heatwaves, they’re also going to create stronger, more frequent cyclones. After 39 years of research covering 4,000 cyclones, scientists published their findings about tropical storms in the PNAS Journal.
Cyclones, also called hurricanes or typhoons, are rotating storm systems with a low-pressure center, and are characterized by strong winds and thunderstorms. Cyclone Amphan, which ravaged Kolkata this morning, is the strongest tropical cyclone recorded in the Bay of Bengal.
Between 1979-2017, researchers studied cyclones around the same time when the climate started changing rapidly, mainly due to human practices. The 39 years of research included eight of the world’s warmest recorded years. They noticed a correlation between the increase in strong cyclones, and the planet’s gradual rising temperatures. Though scientists haven’t ruled out the possibility of other reasons for why cyclones are getting more potent, they have established a significant correlation between global warming and cyclonic activity.
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Cyclones tend to gain and lose speed depending on the surface temperatures of the water surface they originate in, and die out when they hit cooler temperatures or land. Even a single Fahrenheit degree increase in temperature can increase wind speeds by almost 20 miles per hour (32km/hour), making the storm change its category of severity. Over the past century, ocean surface temperatures worldwide have gradually increased by 0.13 degrees Celsius (32 degrees Fahrenheit) per decade. This may explain why recent cyclones are of such high intensity.
“Our results show that these storms have become stronger on global and regional levels, which is consistent with expectations of how hurricanes respond to a warming world,” James Kossin, a scientist and lead researcher on the study, said in a statement. “It’s a good step forward and increases our confidence that global warming has made hurricanes stronger, but our results don’t tell us precisely how much of the trends are caused by human activities and how much maybe just natural variability.”
