It's that time of year again when sweat seeps through T-shirts and shoes feel as if they're melting into the sidewalk.
But severe heat can do far more damage. High urban temperatures have negative effects on air quality, energy consumption, climate resilience, stormwater management and public health. In Chicago, for instance, almost 740 people died during a single weeklong heat wave in 1995.
Several cities across the United States and Canada are now taking steps to mitigate local heat and prevent future warming, according to a new survey by the American Council for an Energy-Efficient Economy (ACEEE) and the Global Cool Cities Alliance (GCCA). Of 26 medium and large cities, two-thirds cited extreme heat events and an increased number of high-heat days as the trigger for adopting policies to address the heat island effect.
Urban heat islands are created by the predominant dark, impermeable surfaces that absorb sunlight and heat-producing human activity like running vehicles and air conditioning systems. This global phenomenon can make cities hotter than surrounding suburban and rural areas by up to 20 degrees Fahrenheit.
"This type of weather, especially when it doesn't cool off at night, can be deadly," said Kurt Shickman, executive director of GCCA.
Between 1989 and 2000, the report states that heat caused more casualties than hurricanes, floods and tornadoes put together. The Centers for Disease Control and Prevention found that between 1999 and 2010 excessive heat caused 7,415 premature deaths in the United States.
Walkable neighborhoods are cooler
Installing reflective and light-colored surfaces on walkways, roads and roofs is one of the most effective ways to address the heat island effect. For instance, U.S. EPA research shows that conventional asphalt can reach 120-150 F in the summer, while reflective pavement stays 50-70 degrees cooler.
Increasing the amount of vegetation in a city is another solution. Plants cool the air through evapotranspiration, remove air pollutants and provide shade.
Reducing the number of exhaust-spewing vehicles in a city by making it easier for people to walk will also mitigate the urban heat island. Walkable neighborhoods have other benefits. Two recent studies released by the American Diabetes Association found that people who live in walkable areas have substantially lower rates of obesity and diabetes than those who live in auto-dependent neighborhoods.
According to the GCCA website, the widespread implementation of the cool technologies could make a city cooler by 4-5 degrees F.
More than half of the 26 cities surveyed said they have requirements in place for reflective and vegetated roofing on private-sector buildings. And nearly every city had policies to increase tree canopy and improve stormwater management.
Washington, D.C., for instance, has put in place a suite of programs, such as Green Alleys, that help residents manage excess stormwater by replacing pavement with grass and trees. In 2009, New York set the goal to coat 1 million square feet of rooftop with light or reflective material each year so that all rooftops would be "cool" by 2035. And in reaction to the deadly 1995 heat wave, Chicago established the goal of having green roofs on 6,000 buildings by 2020.
The heat island report comes as preliminary data released this week by NASA found that global temperatures last month were the warmest of any May on record. NASA highlighted that the results do not yet include data from China and so are not directly comparable to earlier records. However, a separate analysis by the Japanese Meteorological Agency also found that surface temperatures in May 2014 were the warmest of any May in recorded history.
On Tuesday, D.C. set its own record-high temperature of 97 degrees F, surpassing the old record of 95 degrees F set in 1991, according to the National Weather Service. The National Oceanic and Atmospheric Administration will release its global temperature data Monday.
Reprinted from ClimateWire with permission from Environment & Energy Publishing, LLC. 202-628-6500.E&E Publishing is the leading source for comprehensive, daily coverage of environmental and energy issues. Click here to start a free trial to E&E's information services.
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