City Summer Heat Has Intensified With Climate Change

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Urban heat island: Chicago example (
Urban heat island: Chicago example (

City Summer Heat report (Climate Central)Mid-August. A great time for four researchers from Climate Central to publish their new report on urban heat islands—areas with high daily urban vs. rural temperature differences. Almost anybody over 60 will tell you the organization of leading scientists and journalists is right on. My city’s stats are just above.

Though summers in the U.S. have been warming since 1970, cities have been getting hotter faster than the adjacent countryside, as exemplified in 45 out of the 60 cities analyzed. Hundreds of millions of people are affected. Concrete and asphalt roads, buildings, and other infrastructure in cities make them hotter than rural areas. The countryside usually has more plants and trees than impervious surfaces, which hold more heat and release it slower than open green spaces.

How an urban heat island works (

Across all 60 cities that research director Alyson Kenward and her Climate Central team looked at, average city summer heat was 2.4°F hotter than rural temperatures. 57 of the 60 cities analyzed had measurable urban heat islands over the past 10 years. In the summer, their temperatures can be as much as 15-27°F hotter than neighboring areas. The researchers analyzed meteorological data, NASA’s Landsat 8 satellite images, and urban ozone charts to reach these conclusions.

Check the map on the Climate Central site if you live in any of the 60 US cities studied, or know anyone who does (80% of Americans live in cities.). Just click on your city name. You’ll interactively access the facts on local city summer heat.

The 10 cities with the most intense summer urban heat islands over the past 10 years:

  • Las Vegas (7.3°F)
  • Albuquerque (5.9°F
  • Denver (4.9°F)
  • Portland (4.8°F)
  • Louisville (4.8°F)
  • Washington, D.C. (4.7°F)
  • Kansas City (4.6°F)
  • Columbus (4.4°F)
  • Minneapolis (4.3°F)
  • Seattle (4.1°F)

At night, the differences are even more intense.

Hotter temps mean more air pollution (
Hotter temps mean more air pollution (

Heat is the #1 weather-related killer in the U.S., causing everything from heat rash, to heat exhaustion, to swift and life-threatening heatstroke. The hottest days we encounter, particularly days over 90°F, come along with dangerous ground-level ozone pollution levels. Excess ozone can trigger asthma attacks, heart attacks, and other serious health impacts. City summer heat also stresses the electric power grid as the air conditioners all turn on. And grid overuse usually worsens climate change because overworked fossil-fueled power plants release more greenhouse gases than usual….

The study authors point out that urban planning and design that incorporates more trees and parks, white roofs, and alternative materials for urban infrastructure can help reduce the effects of urban heat islands. Too, regional differences call for regionally appropriate solutions. However, they counsel, the rise in temperatures may erase hard-won gains against air pollution since the Clean Air Act and other successful legislation of the past 45 years.

“In the future, this combination of urbanization and climate change could raise urban temperatures to levels that threaten human health, strain energy resources, and compromise economic productivity.”

Where’s the good news here? The good news is that you’re reading this article. The good news is that the more of us who realize change is coming, spread the word, and support proactive planning for it, the better off all of us can be. Plus, the more we are aware of the threats of climate change, the more we are driven to implement the top solutions.

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