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Coastal Desk

New Orleans Ranks As Worst Heat Island In U.S.

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Michael Isaac Stein
/
WWNO
People cool down at a shaded playground on the Lafitte Greenway on a muggy evening in July of 2018.

New Orleans is one of the most significant heat islands in America, according to a new study by the research group Climate Central.

The study finds that on average the city is about 9 degrees hotter than the surrounding countryside. Some areas of the city soar up to 16 degrees hotter.

New Orleans had the highest score, followed by Newark, N.J., New York City, Houston, and San Francisco.

Researchers looked at factors that cause a heat island effect, that is, buildings and pavement that cause cities to be hotter than their outlying areas.

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Climate Central
Climate Central calculated heat retention by looking at albedo - that is how well the city reflects solar energy. They also assessed green space, which cools a city down, population density - the denser, the hotter; and building height - tall buildings have a cooling effect.

Many buildings in New Orleans have black tar shingles and many of the roads are blacktop, both of which cause a city to retain heat. Cities with lighter roofs and light-colored concrete pavement, like Phoenix, absorb less heat.

Tall buildings cool cities down, and New Orleans doesn’t have many of them. Trees and parks also have a cooling effect, as do permeable surfaces, like mulched areas and lawns, which absorb rather than retain heat. The city scored low on all.

Director of climate science, Andrew Pershing, said New Orleans could cool down if the city built more parks, planted more trees, and got people to use lighter colored roofing material.

“Think about how much blacktop pavement you have, which is going to absorb a lot of heat, versus light-colored concrete or light-colored buildings. Think about your roofing materials, that’s going to change the color of a city and it will absorb more heat,” he said.

“The big factor in New Orleans is the ‘albedo.’ New Orleans has a lot of dark-colored roofs and pavement that tends to make the city want to heat up more.”

Recently updated city code discourages cutting down trees and encourages the use of green infrastructure.

Increased heat can have serious health impacts, like heat stress, and can cause dangerous ozone levels. Higher summer temperatures also stress the electricity grid as the use of air conditioners soar.

Support for the Coastal Desk comes from the Walton Family Foundation, the Greater New Orleans Foundation, and local listeners.

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