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Hurricane Ian made landfall in western Florida on Wednesday afternoon with wind speeds close to 150 mph, just shy of reaching Category 5. Huge storm surges flooded coastal areas, with 12 feet of water hitting the city of Fort Myers. Surveillance cameras revealed a wall of water sloshing past storefronts and turning cars into 4-ton bath toys, all while the storm slowed to a hover over the coastline. Moving slowly across the state, Ian then dumped large amounts of rain, flooding inland areas, collapsing buildings, and leaving roads impassable. More than 2.5 million people have been cut off from the grid.
Just a week ago, Hurricane Fiona traveled all the way to Newfoundland in Canada, becoming one of the strongest storms to ever hit the area. And the first major tropical storm to hit the US this year didn’t pass over New Orleans or Miami, but San Diego—a city that almost never sees such weather. Events like these are not unheard of in the historical record, but they have been rare, and their presence during a year when so many other records have been set—from extreme heat in Sacramento to record flooding in Yellowstone—sets off alarm bells. Just as extreme heat and precipitation are growing in intensity and regularity thanks to climate change, the latest research says that strong hurricanes like Ian will become increasingly common too.
“There are a lot of things which are connected, and we’re trying to use models to sort through some of these complicated relationships,” says Thomas Knutson, a senior scientist at the National Oceanic and Atmospheric Administration in the US. He and his colleagues are joining the dots to predict how hurricanes are changing as the world warms.
Hurricanes, or tropical cyclones, are susceptible to rising temperatures—they thrive in warm conditions. In the northern Atlantic they start their life cycle close to the equator, in a globe-encircling region called the tropical convergence zone, where there is a permanent area of low air pressure. Here, thunderstorms are a daily occurrence, and if enough form in a small area, they can begin to fall in toward each other and rotate. Because they cause a steady stream of water to rise up through the warm air, they lower the pressure on the sea’s surface dramatically, meaning they can quickly draw up more water to grow into the most intense storms on Earth. Once this process begins, it takes strong external forces, like powerful winds or a sudden influx of cold air or water, to stop things from intensifying.
And with more warm seawater now stretching poleward because of climate change, hurricanes have the potential to form much closer to the North American coastline. Knutson and his team recently published a paper that found that, because of the spread of warm water, a greater percentage of Atlantic hurricanes could make landfall in the US in the coming decades.
“We simulated fewer storms at the base level, but a greater fraction reaching Category 4 and 5 and making US landfall. What we’re seeing now is an example of that,” Knutson says. This means that hurricane-prone regions in the US could see more storms with winds exceeding 130 mph, powerful enough to rip the roof off a building, uproot trees, and cut off power.
As global average temperatures rise, the atmosphere will also hold on to greater quantities of moisture, meaning hurricanes could unleash stronger torrents of rain—as much as 14 percent more with 2 degrees Celsius warming, according to Knutson. Sea levels are also expected to rise, contributing to stronger storm surges and devastating impacts on coastal areas. “We have very high confidence that sea level rise is going to continue, and that’s going to exacerbate any type of situation like the one we’re seeing now in Florida,” Knutson says.
Most climatologists agree that the intensity of hurricanes and tropical cyclones will increase as global temperatures rise, and that there’s a strong likelihood that they’ve already begun to do so. Since 1980, there’s been an increase in the percentage of hurricanes that reach Category 3 or higher, and storms have started to intensify more rapidly.
At this point, even if nations make good on their COP26 commitments, we’re likely to reach 2 degrees Celsius of global warming—a scenario in which coastal areas in hurricane-prone regions will face an unprecedented existential crisis. Sea level rise will be a general problem, but it will also be a particular threat during extreme weather events, leading to more violent storm surges and overland flooding that will devastate infrastructure and squeeze local and national resources.
Marshall Shepherd, a climatologist and former president of the American Meteorological Society, says the rising threat of tropical storms is a reality that can no longer be ignored—and yet one that we don’t seem to be adapting to. “In some ways these aren’t really natural disasters anymore,” he says. The fact that we keep placing human infrastructure and people in the pathway of these hurricanes, he argues, means that we can’t regard these as freak occurrences, but problems of our own making.
According to the US Census Bureau, Fort Myers, Florida, was the sixth-fastest-growing area in the country from 2020 to 2021. The fastest development there is still occurring along the coastline, with little thought to rising sea levels or an increased likelihood of extreme weather. Mitigation efforts like sea walls can be effective at protecting property from smaller storms, but walls would need to exceed 300 feet in height to protect infrastructure from the most intense hurricanes, at a cost that would exceed the value of the property being protected. “Going forward, there’s got to be realistic and smart growth solutions,” Shepherd says.
What realistic and smart growth will actually look like might be a bitter pill to swallow for those living in coastal inundation zones. Rob Young, a geologist and director of the Program for the Study of Developed Shorelines, says we need to start changing how we rebuild in the aftermath of these devastating storms. “There are probably areas that we simply shouldn’t put any infrastructure back in,” Young says. “But it’s really difficult to make that call after an emergency when everybody’s just trying to make themselves whole again.”
The complete devastation of Mexico Beach, Florida, by Hurricane Michael in 2018, which bombarded the area with 155 mph winds and a 17-foot storm surge, is a prime example, he says. The town’s rebuilding strategy consisted of elevating homes at least 18 feet off the ground to withstand future storm surges. “But they’re still building in a flood zone,” Young says. “We just don’t have the right kinds of incentives or disincentives to change that economic calculus yet—anywhere, not just in Florida.”
Whether or not people reconsider where and how they live, hurricanes and tropical cyclones will almost certainly become stronger and deadlier. The threat is clear—how humanity will respond to it is not.
