Urban Heat — Not A Myth, And It’s Worst Where It’s Wet

A new Yale-led study quantifies for the first time the primary causes of the “urban heat island” (UHI) effect, a common phenomenon that makes the world’s urban areas significantly warmer than the surrounding countryside and may increase health risks for city residents. In an analysis of 65 cities across North America, researchers found that variation in how efficiently urban areas release heat back into the lower atmosphere — through the process of convection — is the dominant factor in the daytime UHI effect. This finding challenges a long-held belief that the phenomenon is driven principally by diminished evaporative cooling through the loss of vegetation. This photo of the United States at night illustrates the bright lights of the nation's urban centers.



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