Tamping Down Urban Heat Islands

Most cities weren't designed with a warming climate in mind. If anything, the aim has been to keep residents warm. Madeline Ostrander writes about how the coming years will force this paradigm to shift. From the piece: "[Georgia Tech professor Brian] Stone had analyzed five decades of temperature data from fifty cities around the United States. He found that the majority were getting hotter than the rural areas around them, and the change was most profound in Louisville—an increase of about 1.7 degrees every decade since 1960."

A big part of the problem, unsurprisingly, comes down to all those heat-absorbing black asphalt roads. "The city had quietly become the country's worst example of what meteorologists call the urban heat-island effect, in which dark, paved surfaces absorb solar radiation, raising the temperature of the air around them." 

Researchers found that Louisville was losing a full fifty-four thousand trees a year, both a result of changing climate and an exacerbating factor for heat. "How many lives could be spared, the researchers then asked, if the city planted more trees and grass, replaced dark asphalt and concrete with light-colored and reflective roofs and pavement, and cut back on the excess heat seeping out of buildings and the tailpipes of cars and buses?" 

Whether cities can take the heat has major implications for public health. "The European heat wave of 2003, for instance, took at least thirty-five thousand lives, a disaster intensified both by global warming and, according to Stone, the heat-trapping design of cities. [A recent study] estimated that if global temperatures rise unabated and the city's population continues to grow, New York could lose more than three thousand lives every year from heat by 2080 (compared with about six hundred in 2006)."