The Worst Types of Cyclones Are Becoming More Likely

India and Bangladesh are currently reeling from Cyclone Amphan. The cyclone made landfall Wednesday, forcing millions into shelters.

Prior to weakening near landfall, it was a super cyclone, the most powerful type of storm possible. A new paper has found that cyclones around the world are becoming stronger. And that’s damn terrifying.

The study, published in the Proceedings of the National Academy of Sciences Monday, looks back at four decades’ worth of satellite data on tropical cyclones, the catch-all term for typhoons and hurricanes. The analysis by National Oceanic and Atmospheric Administration scientists uses an algorithm to control for technical advancements in satellite imaging that may affect the intensity estimates. This dataset isn’t perfect, but Thomas Knutson, a research meteorologist at a different NOAA lab who was not involved in this study, said it’s a “good choice,” especially for the purpose of this study.

The results show that the chances of a cyclone becoming Category 3 or higher—what the National Hurricane Center in the U.S. classifies as a “major” storm—increased by about 8 percent per decade from 1979 to 2017. These types of storms can cause widespread destruction with winds of 111 mph or greater and the potential for punishing rain and storm surge. Category 4 and 5 storms can be even more dangerous to anyone living along the coast.

In the Atlantic, the likelihood increased even further by 49 percent per decade. There was no change in the North Pacific, the most active cyclone basin on Earth, though previous research has shown that storms that make landfall in Asia have become more intense.

Models have long suggested that warmer ocean temperatures driven by climate change would alter tropical cyclone activity, including providing more fuel for them to rapidly intensify. Other research has found that extreme storms, in general, will become more common due to climate change. Scientists have also drawn links between global warming and hurricanes that have already happened, finding that rising temperatures made disastrous events like Hurricane Maria and Hurricane Harvey in 2017 more likely.

The latest study notes this and says there is “a likely human fingerprint on this increase,” though it doesn’t go into an analysis of what’s driving the trend. However, it’s valuable because it adds more evidence to what has previously just been theoretical.

“You have these model predictions about how hurricanes behave with global warming, but it’s good to have data to back up the models,” Knutson said. “If you really want to have confidence that a certain kind of change is going to happen over the 21st century with global warming… you have more confidence in that projection in cases where you’ve already seen the change going on in the data.”

Still, he would like to see further research on the topic. The paper does not show that the increased chances of stronger hurricanes over these 39 years are “unusual” when compared to historical cyclone activity, Knutson said. This could very well be the case, but more research needs to be done on that front.

“You should be able to, especially at some point in the future, have some idea of how unusual the type of change this study is showing is compared to just natural variability in the climate models
,” Knutson said. “It may turn out that it’s very unusual, or it may turn out that it’s on the border or something.”

This research comes at the an unfortunately all-too-perfect time. In addition to Amphan, Atlantic hurricane season kicked off two weeks earlier than normal this past weekend. And even worse, it’s expected to be worse than usual.