The air in these neighborhoods is getting cooler — with huge implications for sweltering cities worldwide.
When the scientists aboard the International Space Station direct their thermal camera at Los Angeles, standing out from the sweltering red and orange blob is a crescent of cool, blueish white deep in the San Fernando Valley.
Greg Spotts, Chief Sustainability Officer of the City’s Bureau of Street Services (Streets LA), is proud of these wintry-looking pixels — not many people can say their work is visible from space. In this area, the center of the Valley’s Winnetka neighborhood, the pavement has been painted with a special reflective coating. “The locations near the cool pavement were, on average, two degrees Fahrenheit cooler than the surrounding area,” Spotts says.
“Previously, our measurements were focused on measuring the surface temperature of the roadway itself, which showed a difference of 10 to 15 degrees Fahrenheit on hot days,” he adds. The satellite thermal camera is significant, however, because it shows that the special cooling pavement not only lowers the temperature on the road, but “produces a cooler neighborhood” in general.
Ten streets in ten neighborhoods have been treated with this cooling paint, and the next phase has just started: This month, bright yellow trucks will roll through West Hollywood and South L.A. to spray white coating on ten streets. “We have identified 200 city blocks across eight underserved neighborhoods for the next phase of urban cooling.”
The record heat waves that scorched the earth from Arizona to Antarctica this year will only get worse, and cities, where heat radiates off buildings and asphalt, will bear the brunt of this heat. “We’ve built our cities like ovens,” Spotts says. “We’re largely using the same materials we have been using since World War II. We need a large-scale change.” According to NOAA, highly developed urban areas can experience mid-afternoon temperatures that are 15 to 20 degrees Fahrenheit warmer than surrounding, vegetated areas. Reducing greenhouse gas emissions tackles the root cause, but in the meantime, cities are looking for ways to lower the temperature. One of the cheapest is to paint roofs and streets white.
The Greek islanders of Santorini, with their whitewashed earthen buildings, were on to something: white surfaces can keep a densely populated area cooler. To this end, New York City has added white, reflective coatings to more than 10 million square feet of rooftop over the last decade. And Los Angeles has installed more than 30 million square feet of cool roofs as part of its new building code. These days, when you visit certain parts of L.A., such as Winnetka or Echo Park, you’ll notice the black asphalt changing to a light grayish-white on more than 50 city blocks.
“At first we thought it might reduce the use of air conditioning and thus help lower associated carbon emissions,” Spotts says, “but we’ve learned that the main driver for this work is public health. We are the only city in the U.S. that records heat-related deaths and emergency room visits in winter.” While Los Angeles is not America’s hottest city (that would be Phoenix), and its climate is tempered by ocean breezes, the heat still carries deadly risks. “We can have hot, humid air in January, and people aren’t prepared,” Spotts knows. “In neighborhoods around the northern rim of the city, the number of days above 95 degrees (35 Celcius) is likely to double, and they already have 40 or 50 of these hot days every year. Can you imagine having 100 days a year of 95 degrees or above?”
For all the concern about worsening hurricanes, floods and tornadoes, severe heat kills more Americans than any other weather event. A recent UCLA study found that higher temperatures even increase the risk of injuries — the researchers estimate that high temperatures already cause about 15,000 injuries per year in California.
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