Ways to keep cities cooler during heat waves
Cities can be miserable during heat waves. All that concrete and asphalt soaks up the sun’s rays, pushing temperatures even higher. Tall buildings can block cooling breezes. Exhaust from cars and air conditioners just adds to the swelter.
This is known as the urban heat island effect: A large city’s built-up environment can make it 2-5 degrees Fahrenheit warmer than the surrounding countryside during the day and up to 22 degrees warmer at night. That extra heat is becoming a serious public health problem. On average, 650 Americans die each year from heat-related causes, the Centers for Disease Control and Prevention estimates, and global warming is only expected to make things worse.
During recent years, some urban planners have been seeking creative strategies to combat the heat island effect to provide relief and prevent more people from dying during brutal hot spells. “Cities need to realize that they have the power to change their own weather,” said Brian Stone, Jr., a professor at Georgia Tech’s School of City and Regional Planning.
Here is a look at a few of the more promising ideas that cities around the world have been pursuing to try to beat the heat. Bring back the trees: This summer in Dallas, where a persistent heat dome has sent temperatures soaring past 105 degrees, volunteers have fanned out around the low-income neighborhood of Oak Cliff, working with residents to plant 1,000 trees around schools and homes.
Trees do not just provide much-needed shade for a sweaty city. The water evaporating from their leaves can cool a neighborhood by a few degrees during the hottest periods. Tree leaves also absorb and filter local air pollution – a crucial benefit, since heat waves can worsen urban smog, sending people to the hospital with asthma and other illnesses.
Seattle now encourages developers to add rooftop gardens or even walls covered by vegetation to new building projects. London recently conducted an audit of its central business districts and identified over 10 million square feet of space that could be converted to rain gardens, green roofs and green walls.
Let the wind blow: In the industrial city of Stuttgart, Germany, refreshing breezes are scarce and valuable. The city sits in a river valley basin, surrounded by steep hills that can trap both heat and polluted air over the region. It is a potentially lethal combination during the hotter months.
In response, Stuttgart has created a number of ventilation corridors throughout the city: wide, tree-flanked arterial roads that help clean air flow down from the hills at night to cool the city. Officials also have re- stricted new buildings from going up on certain hillsides to keep the air moving.
Some experts are skeptical this strategy will work for every city because a lot depends on local weather patterns and geography. But China is becoming interested.
Paint roofs white: One big reason cities are so much hotter than rural areas is they are covered by dark roofs, roads and parking lots that absorb and retain heat. During recent years, many urban planners have sought to replace those dark surfaces with lighter, more reflective materials.
Through its CoolRoofs Initiative, New York City has painted more than 5 million square feet of its roofs with a reflective coating. Los Angeles is replacing some of its dark asphalt roads with brighter materials.
Get people to cooling centers: When dangerous heat waves arrive, access to air conditioning can be a matter of life or death. That is why more cities are setting up public cooling centers to offer relief for those who might lack cool air at home.
But public health experts say setting up cooling centers is only half the battle: The other half is getting people to them. One recent survey of Detroit, Philadelphia, Phoenix and New York found that public cooling centers were often poorly publicized or difficult to access by public transportation.
“There’s this large social and behavioral component to heat waves that doesn’t get nearly enough attention,” said Jalonne L. White-Newsome, a senior program officer at the Kresge Foundation who led the study.
In Philadelphia, many neighborhoods designated block captains who will check on older residents during a heat wave.