Sunday hurricane Ida made landfall in Louisiana, tied with the 2020s Hurricane Laura like the strongest storm that has ever hit the state. Winds of up to 150 miles per hour tore the electrical infrastructure apart, leaving a million people without electricity. The eight transmission lines to New Orleans were cut.
Now temperatures are in the 90s, and the brutal humidity – it’s summer, after all – plunges Louisiana into a multi-layered crisis: Without electricity, residents who don’t have a generator set will also run out of fans or air conditioning. Entergy utility says power may not be restored for three weeks, but local officials warn it could take a month for some. “I’m not happy with 30 days, the people at Entergy are not happy with 30 days,” Louisiana Gov. John Bel Edwards said. noted at a press conference on Tuesday. “No one who needs electricity is happy with this.”
The misery is particularly acute in New Orleans and other cities that are already forming “heat islands“in the landscape. These are places without enough trees or other green spaces where the built environment absorbs the sun’s energy during the day, slowly releasing it at night. Urban temperatures can be 20 degrees Fahrenheit higher. warmer than the surrounding rural areas. And here is the very bad news: a analysis published in July by the Climate Central research group found that the New Orleans heat island effect is worse than any other city in the USA.
If you’re curious about what the hell of the climate crisis looks like, that’s it. “This whole area is already hot and humid all summer,” says Barry Keim, a climatologist at Louisiana State University, who is also a state climatologist. “And you add urban heat island impacts, which just exacerbate that, and you turn off the air conditioning system. It is a recipe for disaster.
Several factors turn cities into heat islands. Concrete, asphalt and brick absorb heat very well. When the ambient air cools down at night, these dense materials can only release part of that heat, so they may still be hot when the sun rises the next day and applies more energy. “So you get some sort of cooking factor over the course of several days of heat,” says Vivek Shandas, a climate adaptation scientist at Portland State University, who has studied the heat island effect in Portland, New Orleans and dozens of other cities. After Hurricane Ida, he said, it now appears New Orleans is facing a “string of excessively hot days.”
The structure of the built environment is also an important factor. High-rise buildings absorb sunlight and block the wind, trapping heat in city centers. And buildings themselves produce heat, especially factories, or exhaust hot air from air conditioning units.
Compare that to rural areas full of trees: when the sun hits a forest or a meadow, the vegetation absorbs this energy, but in turn releases water vapor. In a sense, a green space “sweats” to cool the air, making temperatures much more tolerable.
In an ideal world, every city would be full of trees to help cool it off. But in a metropolis like New Orleans, Shandas says, temperatures can vary wildly, even block by block. Brick buildings retain heat better than wooden ones, and fat freeways bask in the sun. But if the buildings are dotted with trees and you have a lot of green space like parks, all that greenery helps freshen the air.
One day in August last year, Shandas and other researchers compiled 75,000 temperature readings around New Orleans. They found that the coldest areas were around 88 degrees, while the hottest areas soared to 102 degrees. “It has to do with green spaces, it also has a lot to do with the configuration of buildings, as well as construction materials,” says Shandas.