What we know about hurricanes and climate change

Hurricane Ian barreled toward Florida this week and finally made landfall as a Category 4 storm on Wednesday.

Florida remains in a state of emergency as the monster storm is expected to cause catastrophic damage with high-speed winds, powerful storm surges and intense rainfall.

Hurricane Ian, which neared Category 5 conditions, is among the strongest hurricanes to strike the U.S. in recorded history after it made landfall in Florida with 150 mph wind speeds.

The storm is renewing concerns about the ties between climate change and major hurricanes, which are becoming more intense as the globe warms.

Allison Wing, an associate professor in the department of earth, ocean and atmospheric science at Florida State University, told The Hill that stronger storms and sea level rise “combined with the increases we’ve seen in coastal population and infrastructure” is a major concern for the U.S.

“It’s a scenario in which coastal cities in the U.S. are more prone to the occurrence of [hurricane-]related disasters,” she said. “It’s something that we need to think carefully about and better prepare for.”

Wing said climate scientists use three scientific methods to determine the correlation between climate change and hurricane development: observation, climate models and a general theoretical understanding of concepts and academic fields such as physics.

Based on climate science, here’s what we know definitively about the development of hurricanes as the climate rapidly warms.

Warmer oceans increase wind speeds; warmer atmosphere increases precipitation rate

While we often think about the atmosphere warming, oceans are also heating up because of climate change.

Ocean heat content has skyrocketed from 1955 to 2019, according to the National Oceanic and Atmospheric Administration’s (NOAA) database.

Wing said a major concern is that warmer oceans are rapidly intensifying wind speeds, which is the measurement used to categorize hurricane strength on the Saffir-Simpson scale.

Some of the strongest hurricanes to strike the U.S. have landed in the past few years, including Hurricane Michael, hitting Florida with 158 mph wind speeds in 2018; Hurricane Ida, which struck Louisiana with 150 mph wind speeds in 2021; and Hurricane Laura, which slammed into Louisiana with wind speeds of 150 mph in 2020.

A warmer atmosphere also means there is more moisture trapped in the atmosphere, creating riper conditions for more intense rainfall.

With a higher rate of rainfall, the soaring inches of water descending on communities as a result of the precipitation drastically increases flooding.

NOAA predicts that based upon global average temperatures reaching 2 degrees Celsius, rainfall rates from hurricanes will increase by 10 to 15 percent within a distance of about 60 miles from the storm.

Wing said it’s not yet clear whether climate change is tied to longer periods of rainfall, which is more closely connected to how long the storm remains in one area.

Storms intensify faster and are more likely to intensify

NOAA estimates the intensity of major hurricanes and tropical cyclones (another name for hurricanes) are expected to increase between 1 percent to 10 percent in a 2 degree Celsius world.

The proportion of storms reaching a Category 4 or Category 5 level is also expected to increase in that scenario.

The frequency, or the number of hurricanes that form, is not expected to increase in a warming world, since information on that is not definitive. But climate scientists do expect a rapid intensification of those storms that do form.

Wing said that Hurricane Ian is a good example of rapid intensification, when the speeds increase by at least 35 mph in a 24-hour period.

“It’s something that typically doesn’t happen that often,” she said, “but has been happening more often frequently.”

Sea level rise makes storms more dangerous

Another factor is not directly tied to the storms themselves, but contributes to the damage a hurricane can cause.

Climate change is melting ice glaciers in the Arctic and expanding seawater, raising sea levels across the globe.

According to NOAA, the U.S. coastline is expected to see sea levels rise somewhere between 10 to 12 inches in the next 30 years.

Rising sea levels are breeding grounds for disasters when a hurricane hits, Wing said.

“A 12-foot surge comes along and you have more areas underwater or you get a surge that in the past would not have put you over the seawall — but now these days that same surge would,” she said. “Higher sea level is just sort of priming the environment to have the worst flooding impacts.”