Extreme summers like that of 2012 — which saw record temperatures in cities across the U.S. — may be atypical, but experts say they will return, especially as the planet warms under climate change. And as they do, cities will be especially vulnerable.
Extreme summers like that of 2012 — which saw record temperatures in cities across the U.S. — may be atypical, but experts say they will return, especially as the planet warms under climate change. And as they do, cities will be especially vulnerable.
A new University of Wisconsin-Madison study details how extreme temperatures affect urban heat islands — densely built areas where heat-retaining asphalt, brick and concrete make things hotter than their nonurban surroundings.
The study, published last week in the journal Environmental Research Letters, found heat waves hit urban areas hardest, shedding light on what a future with more extreme summers might mean for the world's growing population of urbanites.
Since heat islands tend to be the most densely populated areas of the city, as the chances of a heat wave rise, many city-dwellers could face more uncomfortable summers, increased health risks and potentially higher energy bills from air conditioning.
"Not only do heat waves intensify the urban heat island, but the heat island also intensifies the heat wave, which is pretty much the opposite of what you'd want," says the study's lead author, Jason Schatz, a postdoctoral researcher on the Water Sustainability and Climate Project at UW-Madison.
By nature, extremes are rare. But Schatz got a stroke of luck when, within the first three years of the study, their study site and Wisconsin's capital city, Madison, was hit with both the 2012 heat wave and the polar vortex of 2013-14, which caused the coldest winter in 35 years.
Using data from the 150 sensors Schatz installed in and around Madison, the researchers found that urban areas experienced up to twice as many hours over 90 degrees Fahrenheit than rural areas during the 2012 heat wave.
The densest urban areas also spent over four consecutive nights in temperatures above 80, the National Weather Service's nighttime heat advisory threshold. Since prolonged heat exposure, rather than isolated hot days, is what can cause heat stress, long stretches with no nighttime reprieve in densely populated areas pose a greater risk to public health.
Continue reading at the University of Wisconsin-Madison.
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