USA: How cities can cool down urban heat islands
By Emma Coleman
More than 80% of Americans live in cities, which tend to be hotter than rural areas due to the “urban heat island” effect—where the high density of buildings, parking lots, and pavement absorb and retain heat. These higher temperatures can exacerbate health problems like asthma, create dangerous conditions for vulnerable populations, and escalate energy consumption and greenhouse gas emissions from people using more air conditioning.
As climate change makes heat waves more frequent, cities are particularly susceptible to temperature spikes because of their urban heat islands. Mayors have asked residents to stay inside on hot days, high temperatures have forced school closures, and cities are setting up dedicated cooling centers for residents that lack AC. In short, heat is becoming a crisis in cities, and municipal leaders are searching for solutions.
Shandas and a team of researchers recently worked on a new process for measuring temperature across a city, one that recruits volunteers through community groups to get on-the-ground data. Volunteers in 20 U.S. cities attached thermal monitors to their cars and drove slowly down streets in their cities this summer, collecting data on a hot day with no clouds during the morning, afternoon, and evening. They found some surprising results. In many cities, there was a 15 to 20-degree temperature difference between different neighborhoods. In West Palm Beach, Florida, Shandas said, the heat index hit 120 degrees in some places, while other areas didn’t even break 90.
Shandas explains that there are six main factors that influence hyperlocal heat islands: the height of the tree canopy, the volume of the tree canopy, the amount of vegetation on the ground, the volume of buildings, the difference in height between those buildings, and the buildings’ coloring. Many low-income neighborhoods or communities home to people of color often lack older trees and ample lawns, as well as being the location for some of the most dense building patterns in a city.