Mapping a threat: Climate change’s deadly summer heat may deepen disparities in Chicago

CHICAGO -- Every year, Chicagoans relish the onset of “Summertime Chi,” when the frigid winter gives way to summer heat and outdoor spaces come alive with concerts and neighborhood festivals. But the rising temperatures that make Chicago more vibrant can also be deadly.

As climate change increases the frequency and intensity of heat waves, city dwellers face extra risk thanks to the urban heat island effect, in which man-made changes to the environment drive up temperatures in metropolitan areas.

Within cities, too, heat disparities can place disadvantaged populations in additional danger. For people living in consistently hotter areas, there’s typically fewer shade trees offering shelter from the sun, little extra money to pay for air conditioning, obstacles in getting medical care for health conditions that pose deadly risks in extreme heat.

To intervene where aid is most needed, local officials and organizations in dozens of cities have participated in a National Oceanic and Atmospheric Administration program launched in 2017 to map heat disparities and raise public awareness. But Chicago has never applied, according to NOAA.

So the Tribune set out to identify which communities may be more at risk and assess whether the city’s government is doing all it can to help them survive before the next heat wave strikes.

Compiling a decade’s worth of temperature data gathered by satellites and analyzing it by U.S. census block group brought the city’s historically hottest areas into view. Though the land surface temperatures recorded by the satellites are more extreme than air temperatures, these readings represent the best available option to track differences. The resulting map, produced in collaboration with researchers at Boston University’s Center for Climate and Health, is the most detailed picture to date of disparities in heat exposure across the city.

Census estimates indicate that more than 300,000 people live in areas where average summer surface temperatures are hotter than 90% of the rest of Chicago, or an estimated 5 to 10 degrees warmer than the city average. Latino residents disproportionately shoulder the burden of Chicago’s heat disparities, the data show, while white residents disproportionately benefit from living in areas with the coolest average temperatures.

The local aphorism that it’s “cooler by the lake” can’t fully explain these