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One problem with finding climate change signals in tropical storms is that they are relatively infrequent events, and having the right mix of ingredients doesn’t always mean that a storm will form. There is a lot of variability in hurricane patterns, both year to year and over the course of decades. That makes it hard to suss out trends and even harder to identify signals in individual storms.
Hiroyuki Murakami, a scientist at the Geophysical Fluid Dynamics Laboratory at NOAA, likened the link between climate change and hurricanes to the link between smoking and cancer.
“When you look at the individual person, it’s really difficult to say that this person got lung cancer because they smoke a lot, because there are many people who smoke a lot but still they don’t get cancer,” Murakami said. “This is really similar. I think that probably there are some storms affected by climate change, but it’s really difficult to say that this storm is only attributable to climate change.”
That said, scientists are starting to see some trends underway. With rising average temperatures, oceans are warming. That means when hurricanes do form, they can be stronger.
“We’ve identified that global warming, climate change, can intensify storm mean intensity,” Murakami said. “In terms of storm intensity, it’s really simple: The source of energy for a tropical cyclone is warm ocean evaporation. When we get a much warmer ocean surface, it will lead to more evaporation to energize a tropical cyclone.”
According to a study last year in the Proceedings of the National Academy of Sciences, tropical cyclones have grown more intense between 1979 and 2017. “The results should serve to increase confidence in projections of increased [tropical cyclone] intensity under continued warming,” the authors wrote.
As for the frequency of hurricanes, that’s more complicated, and it’s not clear how climate change will alter the number of major storms that do occur. “A lot of models project a decreasing tropical cyclone number, but still we don’t know yet why climate models show decreasing tropical cyclones in the future,” Murakami said.
He pointed out that even in 2020’s extremely active season, only a couple of the tropical storms turned into major hurricanes. So climate change doesn’t necessarily mean more hurricanes, but a growing proportion of those that occur will likely be more powerful.
Perhaps the most concerning impact of climate change on tropical storms is that it is worsening the most destructive elements of these events. It’s not the wind that usually does the most damage during a hurricane, but flooding. That’s why changes in precipitation patterns can be a major concern.
“A difference between 1 to 2 inches of rainfall is the difference between whether your house gets flooded or not,” said Stony Brook’s Reed.
That flooding in the wake of hurricanes is caused primarily by rainfall and storm surges. Winds from tropical storms can push coastal water inland, creating storm surges. Melting ice and warming oceans due to climate change are causing sea levels to rise, so when storm surges do occur, they reach greater depths and further inland, causing more destruction.
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