New Orleans Was Already a ‘Heat Island.’ Then Ida Cut the Power
Sunday hurricane Ida made landfall in Louisiana, tied with Hurricane Laura of 2020 as the strongest storm on record in the state. Winds reaching 150 mph ripped through the electrical infrastructure, leaving a million people without power. All eight transmission lines to New Orleans have been cut.
Now the temperatures are in the 90s and the brutal humidity – it’s summer, after all – is plunging Louisiana into a multi-level crisis: Without electricity, residents who don’t have a generator will also run out of power. fans or air conditioning. Utility Entergy 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 the 30 days, the people at Entergy are not happy with the 30 days,” Louisiana Governor John Bel Edwards said at a press conference on Tuesday. “No one who needs electricity is happy with this.”
Poverty is particularly acute in New Orleans and other cities that already form “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 warmer than surrounding rural areas. And here’s the really bad news: An analysis released in July by research group Climate Central found that New Orleans’ heat island effect is worse than any other city in the United States.
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 long,” says Barry Keim, a climatologist at Louisiana State University, who is also a state climatologist. “And you add urban heat island impacts, which only 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 this 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.