Scientists suggest white paint, more trees can lower temperatures in cities

With record global temperatures stoking droughts and deadly heat waves, some scientists are eyeing audacious schemes to counteract the rising mercury—from enormous air filters to suck carbon dioxide from the air to launching millions of sunlight-deflecting space mirrors into orbit around the planet.

Other scientists see the value of simpler tools: shovels and paintbrushes, The Wall Street Journal reports. The shovels are for planting trees, whose shade has been shown to lower air temperatures in sweltering cities by up to 45 degrees Fahrenheit; the brushes for painting rooftops and other dark surfaces light colors that limit the absorption of temperature-raising sunlight.

Temperatures in cities have risen faster than the rest of the globe since 1960, according to an analysis of temperature trends in 50 major U.S. cities published recently in the journal Landscape and Urban Planning. Other studies show that a city of a million people can be 1.8 to 5.4 degrees Fahrenheit warmer than the surrounding countryside, with a nighttime temperature difference of up to 22 degrees. Climate scientists say that difference is the result of concentrations of dark-colored, heat-absorbing rooftops, building materials and roads in urban areas. 

As a result, urban heat waves are becoming more intense, putting residents at risk of power outages when the air conditioners are cranked up, which have doubled in the past five years, according to a study published recently in Environmental Science and Technology.

In cities across the U.S., urban foresters have started planting trees by the million. Other researchers are perfecting the whitest white paint ever developed, to better reflect the sun’s rays, and promoting lighter roofing materials. Read the full story.