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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].
Update
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).
