Ida was a fierce Category 4 hurricane when it came ashore Sunday in Louisiana. With sustained winds of about 150 mph, the storm ripped roofs off buildings and snapped power poles. It pushed a wall of water powerful enough to sweep homes off foundations and tear boats and barges from their moorings.
Climate change helped Ida rapidly gain strength right before it made landfall. In about 24 hours, it jumped from a Category 1 to a Category 4 storm as it moved over abnormally hot water in the Gulf of Mexico.
The ocean was the temperature of bathwater — about 85 degrees Fahrenheit. That's a few degrees hotter than average, according to measurements by the National Oceanic and Atmospheric Administration.
The extra heat acted as fuel for the storm. Heat is energy, and hurricanes with more energy have faster wind speeds and larger storm surges. As the Earth heats up, rapidly intensifying major hurricanes such as Ida are more likely to occur, scientists say.
The trend is particularly apparent in the Atlantic Ocean, which includes storms such as Ida that travel over the warm, shallow water of the Caribbean Sea. A 2019 study found that hurricanes that form in the Atlantic are more likely to get powerful very quickly.
Residents along the U.S. Gulf Coast have been living with that climate reality for years. Hurricane Harvey in 2017, Hurricane Michael in 2018 and Hurricane Laura in 2020 all intensified rapidly before they made landfall. Now Ida joins that list.
Hurricanes such as Ida are extra dangerous because there's less time for people to prepare. By the time the storm's power is apparent, it can be too late to evacuate.
Abnormally hot water also increases flood risk from hurricanes. Hurricanes suck up moisture as they form over the water and then dump that moisture as rain. The hotter the water — and the hotter the air — the more water vapor gets sucked up.
Even areas far from the coast are at risk from flooding. Forecasters are warning residents in Ida's northeastward path to the Mid-Atlantic that they should prepare for dangerous amounts of rain. Parts of central Mississippi could receive up to a foot of rain on Monday.
AUDIE CORNISH, HOST:
It's the day after in Louisiana, the day after the massive and devastating Hurricane Ida made landfall as a major Category 4 storm. Louisiana Governor John Bel Edwards spoke about the damage earlier today.
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JOHN BEL EDWARDS: We are still in a life-saving mode here, doing search and rescue. The roads, the highways into the most affected area were completely clogged with debris.
CORNISH: Rebecca Hersher from NPR's climate team is here with more about how climate change helped Ida get big, powerful and destructive. Rebecca, I want to just set the stage here. This is peak hurricane season in the U.S. It's normal to see powerful storms this time of year. What is it about climate change that is affecting a storm like Ida?
REBECCA HERSHER, BYLINE: So climate change is basically supercharging this storm. So what climate change does is it adds fuel to a hurricane, fuel in the form of heat. So hurricanes form over water. You can think of them like engines spinning up like a propeller on a plane. And the energy for that propeller comes from the heat in the water. As the Earth gets hotter because of climate change, the water on the surface of the ocean - it also gets hotter. So there's more energy for storms like Ida to get really big and really powerful.
CORNISH: What's the evidence for that? How do we know this happened with Ida specifically?
HERSHER: So we can basically observe it in real time, which is pretty terrifying. So, for example, let's talk about the wind. On Saturday, the day before Ida made landfall, it had top wind speeds of about 85 miles an hour, which is pretty serious. It can remove shingles from a roof or snap off the limb of a tree. But overnight, the storm got a lot more powerful. The top wind speeds jumped to about 150 miles an hour. That is fast enough to tear whole roofs off of houses, snap power poles, you know, uproot entire trees. And that extra power - it came from the water in the Gulf of Mexico.
CORNISH: What do you mean by that? How, like, warm was that water?
HERSHER: It was basically like a bathtub - about 85 degrees, which is a few degrees warmer than average if you look at measurements from the National Oceanic and Atmospheric Administration. So weather forecasters could watch the storm feed on that heat. And when a hurricane gains that much power that quickly, scientists call it rapid intensification. So studies have found that hurricanes are more likely to rapidly intensify because of global warming. And people who live on the Gulf Coast of the U.S. - they are on the frontlines of this. You know, Hurricane Harvey did this in 2017, Michael in 2018, Laura in 2020 and now Ida. They have all rapidly intensified.
CORNISH: Does the speed of the intensity translate to a more powerful storm?
HERSHER: Yes. Yes, it does. And it also gives people less time to prepare. So when we're talking about these really fast wind speeds that come really quickly, you know, there's less time. There might not be time to evacuate by the time you know the storm is going to be that powerful. And the National Weather Service tries to get around this by putting out warnings, saying basically, you know, this storm is likely to get a lot stronger before it makes landfall. But it can be really hard to convince people to take a storm seriously when it intensifies really late.
CORNISH: Ida at this point is a tropical storm. It's heading northeast. Is climate change playing a role in kind of what happens next, how it's moving?
HERSHER: Yes, absolutely. So the hot water in the Gulf of Mexico also helped the storm sucked up moisture that falls as rain. It is really important to remember that these storms can cause flooding really far inland. So in Mississippi, we're going to see a lot of flooding. And then the track goes through central Tennessee, where they just had a lot of deadly flash floods. So people in the path need to take those flood warnings really seriously.
CORNISH: That's Rebecca Hersher from NPR's climate team. Thank you for your reporting.
HERSHER: Thanks so much.
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