50 years ago, scientists warned of the ‘neglected dangers’ of heat islands

Excerpt from the October 20, 1973 issue of Science News

Person riding a bicycle in Phoenix during a period of extreme heat.

A person rides a bicycle in Phoenix on July 25, 2023, during a period of extreme heat. Cities already run hotter than outlying areas, an effect that’s made worse by climate change.

Mario Tama/Getty Images

Neglected dangers of thermal pollution Science News, October 20, 1973

Most urban dwellers have experienced the swelter of a summer night in the city, but higher temperatures in the atmosphere over such “heat islands” may have more insidious effects, which urban planners seldom consider.… Urban-rural temperature differences can be as high as 18 degrees [Fahrenheit].


Today, excess heat from pavement and buildings cause U.S. cities to run half a degree to 4 degrees Celsius (1 to 7 degrees F) higher on average than outlying areas. This heat island effect is expected to worsen as a side effect of climate change. Because urban areas are expanding, that means their growing populations are at risk for heat-related illness or death, scientists reported in 2019 in Environmental Research Letters. To stay cool, some cities are switching to roofs and surfaces that reflect a lot of sunlight and heat. Adding trees helps too: Trees provide shade and emit water vapor that lowers air temperature, almost like if a city could sweat (SN: 4/14/18, p. 18).

Erin I. Garcia de Jesus is a staff writer at Science News. She holds a Ph.D. in microbiology from the University of Washington and a master’s in science communication from the University of California, Santa Cruz.

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