Summer in the city: Hot and getting hotter
This report documents summer temperatures in 60 of the largest U.S. cities, investigating the urban heat island effect, the average number of extreme hot days per year, and the effect of heatwaves on air pollution.
It finds that in two-thirds of cities analysed, urbanisation and climate change appear to be combining to increase summer heat faster than climate change alone is raising regional temperatures. In three quarters of cities examined, urbanised areas are warming faster than adjacent rural locations.
It notes that several independent studies have shown that urban heat islands (in the U.S., and around the world) do not bias global warming measurements, ruling out the possibility that rising global temperatures have been caused by urbanisation alone. Research suggests 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. But rising greenhouse gas emissions are projected to drive average U.S summer temperatures even higher in the coming decades, exacerbating urban heat islands and their associated health risks.
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