As heat island effects worsen due to climate change, cities try to adapt

Buckling roads and melting streetcar cables during the record high temperatures in the Pacific Northwest illustrate that “heat wave” is a buzz word this summer, and scientists blame climate change. The heat waves exacerbate the urban heat island effect, in which city temperatures are several degrees hotter than their surrounding areas largely due to manmade infrastructure like buildings and roads absorbing and re-emiting the sun’s heat. Many cities aren’t sitting idly by: They’re implementing cooling measures to improve health, safety, resilience and livability.

Cooling concepts

Recent research on urban heat islands has brought increased awareness to the effects it has on residents and wildlife, its ties to climate change and the actions that could help cities lessen the hazards.

Bangor, Maine; Chicago; Denver; and Portland, Oregon are among the slew of cities turning to the short-term solution of setting up cooling centers to offer residents relief during heat waves and reduce the risk of excessive heat-related health incidents. But cooling centers don’t reduce a city’s heat intensity. Many cities are implementing long-term strategies to reduce the urban heat island effect by rethinking and reworking future development and adding natural or built infrastructure to cities: trees and green spaces, green roofs, reflective “cool roof” coatings and “cool pavement.”

In 2015, Los Angeles tested a light gray pavement coating on a city parking lot that reflects more sunlight than dark asphalt. The cool pavement absorbs less heat to keep street surface temperatures cooler, sometimes by dozens of degrees. After launching another pilot in 2017 in residential neighborhoods, L.A. saw surface temperatures drop 10-20 degrees in areas with the cool pavement. 

Los Angeles was one of the first cities in the U.S. to pilot cool pavement at “a reasonable scale,” said Kurt Shickman, executive director of the Global Cool Cities Alliance. The city also installed new manmade and natural shade coverings, provided access to potable water and identified not just where it’s hot but where people are actually spending time outside, he said. 

“They’ve done a nice job of looking at where people are walking in Los Angeles… and thinking through what kind of passive cooling measures could be applied in areas where people congregate or are walking to reduce heat stress,” Shickman said.

Phoenix is currently running a cool pavement pilot and anticipates publishing preliminary results by the end of this year. Phoenix is also in the process of updating its climate action plan, which includes a section dedicated to heat. Strategies include increasing shade overall and creating a network of 30 “cool corridors” in vulnerable communities by 2030 with more shade along specified routes that people travel between home, work and entertainment. 

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