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Urban heat

Cities sizzle as more people move in

In life, as in boxing, the combined effects of a one-two punch are often more devastating than either blow alone. Imagine, then, the devastation from a triple whammy that city dwellers might suffer this century as three unfavorable trends converge to afflict an already warming world.

First, there’s temperature. According to the Intergovernmental Panel on Climate Change, Earth’s average global temperature has risen about 0.74 degrees Celsius in the past century (SN: 2/10/07, p. 83), an increase almost certainly linked to the rising concentrations of carbon dioxide and other heat-trapping greenhouse gases that human activities have released into Earth’s atmosphere. IPCC scientists suggest this warming trend will continue, and indeed accelerate: In the next 20 years, average global temperature will rise another 0.4 degrees C or so, they estimate.

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