As Temperatures Rocket, Cities Fight Heat Waves

In the coming decades, heat waves will be longer, more frequent and more intense in many parts of the country, according to the 2014 National Climate Assessment.  This summer alone, extreme heat has killed grape pickers in California fields and hikers in Arizona.  At least four people died of heat-related illnesses in El Paso, Texas, where the city saw 16 days in a row of temperatures exceeding 100 degrees, the third-longest stretch ever.  Phoenix saw its hottest combined June and July on record, with temperatures averaging 96 degrees daily.  And higher-than-average temperatures and drought have scorched corn and peanut crops in Tennessee and Georgia.

When nighttime lows go high
People who respond to heat waves are especially alarmed by a specific climate change trend:  the rise in nighttime lows in some places during the summer.

In many cities, temperatures aren't cooling at night in the summer the way they once did.  In Washington, D.C., this summer, for example, the temperature stayed at 70 degrees or above at night for 35 days straight in July and August, a record in 145 years of record-keeping, The Washington Post reported.

"When we look at how extreme heat affects our health, we see the most impacts when we have multiday events and when nighttime temperatures don't cool off enough to give us a respite," said Katharine Hayhoe, director of Texas Tech University's Climate Science Center.

"So when we don't get a break, when those daytime highs just keep getting higher and higher, and when it doesn't cool off enough at nighttime, that's when we start to see impacts on our health," she said.

Such a trend means people can expect less relief from cooler air at night in the summer, a worrisome climate shift where people rely on cooler nighttime temperatures to ease the discomfort of the day.  That's especially crucial in some parts of the Midwest or Pacific Northwest, where air conditioning isn't as common.

There are studies that show the cooling needs of the body are most crucial at nighttime, said Shalini Gupta, executive director of the Center for Earth, Energy and Democracy in Minneapolis.  Yet few cities have taken that into consideration with their planning.  Cooling centers may not be open at night — and malls and other public facilities open to people during the day are also closed.

Cities could be doing a better job of planning more comprehensively, said Cecilia Martinez, director of research programs at CEED.

"A lot of cities have climate action plans in terms of mitigation," she said.  "More are developing climate adaptation plans.  But we still need much more work on climate action plans or climate resiliency plans that can address the climate impact of heat waves."

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