Formerly redlined areas now are often urban heat islands

·3 min read

Heat is typically the No. 1 weather-related killer in the U.S. — but depending on the neighborhood, some city residents experience cooler, more manageable temperatures than others.

Why it matters: All cities trap heat, with their darkly colored asphalt and energy absorbent buildings — a phenomenon known as the Urban Heat Island effect. However, within these heat islands, some areas are consistently hotter.

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  • They are often the same redlined neighborhoods where historically, banks refused to underwrite mortgages and loans and insurance companies refused coverage based on race and ethnicity, Jeremy Hoffman, a climate scientist at the Science Museum of Virginia, tells Axios.

Driving the news: When a heat wave struck the Pacific Northwest in June, possibly killing more than 600 people, Portland and Seattle residents sweltered through triple-digit temperatures.

  • Wealthier areas had more shade to protect people from the sun and prevent solar radiation from reaching dark sidewalks, keeping those areas cooler. This may have meant the difference between life and death, especially because it lowered temperatures at night and allowed people to recover.

  • With global warming leading to more intense and frequent heat waves, there is growing urgency for scientists and policymakers to address heat exposure disparities within communities.

The big picture: Researchers using grants from the National Oceanic and Atmospheric Administration have mapped the urban heat islands of dozens of major U.S. cities and found that the effects of redlining stand out.

  • Poorer neighborhoods with more Black, Latino, Asian or Native American residents tend to have fewer trees and parks, as well as fewer neighborhood interventions to reduce temperatures outside and inside homes, such as white and green roof projects.

Details: One study published last year in Climate found that land surface temperatures in formerly redlined areas are about 2.6°C, or 4.7°F, warmer than other locations in the same cities.

  • “People that are living in these areas are experiencing a very different day-to-day environmental experience than people living in the same cities just a few blocks away,” Hoffman says.

How it works: Vivek Shandas, a professor at Portland State University, views heat as an “insidious climate justice issue.” He says heat exposure has been "pre-baked" into communities due to legacy policies on infrastructure, housing and health care.

Between the lines: Jane Gilbert is the first chief heat officer of any U.S. metro area. She serves Miami-Dade County, Florida, which includes the city of Miami, and has been examining the heat exposure differences there.

  • In a trend due in large part to human-caused climate change, since 1970 Miami has seen a 79-day increase in the number of days each year with temperatures above 90°F, according to data from the nonprofit science and journalism group Climate Central.

  • Gilbert says the heat-related threat that keeps her up at night is a large-scale power outage, or a prolonged power outage following a hurricane strike.

  • Case in point: Heat turned deadly this year in New Orleans following Hurricane Ida.

What's next: Miami-Dade County is looking for ways to address disparities in heat exposure within communities.

  • Gilbert says she is working with the National Weather Service to try to lower their thresholds for issuing heat alerts that trigger things like opening cooling shelters.

  • The urban heat island effect means that some neighborhoods exceed warning criteria on days when no warnings are issued, Gilbert says, primarily because the temperature at official measuring stations is cooler.

  • Miami-Dade County is working to increase the tree canopy in poorer neighborhoods to provide more shade, and they’re also pursuing weatherization and other efficiency retrofits to reduce energy consumption at home. This is part of an effort to enable more residents to afford air conditioning.

  • In addition, the county is training responders to check on vulnerable residents during heat waves.

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