How Hurricane Ian intensified so quickly

To understand hurricanes and climate, follow the water.

As I pulled my car onto the interstate traveling east, out of Tampa Bay, I was following the water. The first rains of arrived late Monday, and I was driving through the torrential downpour, headed home after a climate panel discussion in St. Petersburg. Rains slowed and the distant southern skies shone a pale yellow, moving through warm pinks, and settling on a sickly shade of green. Beautiful and ominous warning signs of the storm to come.

While I drove, Hurricane Ian exploded into the major hurricane it was predicted to become. Late Sunday, Ian was a tropical storm south of the Cayman Islands. By late Tuesday, it was set to reach Category 4 intensity (more than 130 mph), potentially reaching the Tampa Bay area on Wednesday as the first major hurricane in more than 100 years to make landfall there. No matter what, it will push a devastating surge of water onshore and flood streets with rainfall totals measured in feet. When it comes to hurricanes in a warmer world, it’s about the water.

It starts in the ocean. Warm ocean waters fuel hurricanes — the warmer the water, the faster the storm can spin and the more powerful and damaging the storm can be. And climate change has warmed the waters beneath Ian by 1- to 2 degrees Fahrenheit since 1970. Warmer waters also increase the chances that a storm will go through a period of rapid intensification (defined as a 35 mph increase in wind speed over a 24-hour period). Ian’s rapid growth from tropical storm to major hurricane is a textbook example of rapid intensification, something that is becoming much more common for tropical cyclones across our warmer oceans.

Water expands as it warms, so there’s more of it in a warming world. Melting at the poles and elsewhere adds to the expanding oceans, pushing sea levels higher and coastal flooding further inland. Because of climate change, Hurricane Ian’s storm surge will arrive on top of a higher sea, reaching more homes, causing more damage.

Increased damages from attributably higher water levels can run into the billions of dollars. For instance, a Climate Central study last year showed that the human-caused sea-level rise tapped by Hurricane Sandy in 2012 cost an additional $8 billion, driving 12 percent of Sandy’s total damages experienced in New York, New Jersey, and Connecticut.

A hotter climate also means heavier rainfalls. For every Fahrenheit degree increase in air temperature, the atmosphere can hold 4 percent more moisture — and globally, we’re approaching a 2-degree increase since pre-industrial times. That means more water can fall as rain, especially during hurricanes.

Warm water is also a big reason so many people are in harm’s way. It’s what makes Florida so appealing, luring hundreds of thousands of new residents every year to growing communities like Tampa Bay — where I’m from. I’m a Floridian and I understand the risks, but I also understand the appeal that makes so many of us accept those risks. For most, it’s all about the water.

But water is also what typically causes damage during hurricanes, from coastal flooding and heavy rain — even though we use wind speed to describe storms’ intensity. It’s almost assured that Hurricane Ian will qualify as a billion-dollar disaster when the costs are tallied, and water will account for the bulk of the losses.

Those costs won’t be distributed equally; climate change is inevitably unfair. Even when damage is most visible along the water’s edge, people living just beyond the shorelines often face the hardest losses: Lower-income communities, Black and brown communities, hourly workers and renters. People more likely to be underinsured, with less access than their neighbors to adaptation measures in advance of the storm, to support services, and to recovery funds. People whose incomes disappear while businesses are closed for repairs, or never reopen. The waters may be rising at the same rate for everyone across my home state, but not everyone has equal access to resources and opportunities to stem the tides.

Dangerous waters in a warming world are the new normal. Climate science can’t (yet) predict how often storms like Ian will rapidly intensify into major hurricanes, but the risks have been rising for decades, and the chances of disasters like this will only increase as the planet warms. Living by the water will only get more dangerous.

Today, Floridians are focused on doing what they can to protect their properties and livelihoods. In the future, our focus might shift to how to live in this warming world. Maybe, even as the beauty of the coast draws us toward the shore, we’ll learn to live in ways that mitigate the rising water’s increased risks and shield the most vulnerable from its harms.

As I drove inland anticipating my own preparations, the torrential gray became a sickly green, giving way to a sprinkling twilight navy and then a dry moonless darkness. As quiet settled over my stop-and-go drive surrounded by Tampa Bay’s evacuees, I realized I wasn’t just following the water — it was also following me. The water is following all of us, in our shared warmer world.

Daniel Gilford, Ph.D., is a meteorologist and atmospheric scientist. His work at Climate Central focuses on attribution research and sea-level rise.