Using lighter colors for rooftops and streets worldwide could help reduce global temperatures and offset the heat from as much as two years of global greenhouse gas emissions, according to a new study. After examining the results from a global land surface model from NASA Goddard Space Flight Center, researchers at the Lawrence Berkeley National Laboratory determined that increasing the reflectivity of roofs and pavement in cities with populations greater than 1 million would have a one-time cooling effect equivalent to reducing global CO2 emissions by 57 billion metric tons, according to a study published in the journal Environmental Research Letters.
Roofs and pavements cover 50 to 65 percent of the planet’s urban areas, helping to contribute to the so-called urban heat island effect, in which cities are significantly warmer than surrounding areas. That warmth radiates into the atmosphere, which is then absorbed by clouds and trapped by the greenhouse effect. More than half of the world’s population now lives in urban areas, and experts predict that figure will reach 70 percent by 2040. As part of an initiative to promote a transition to cooler surfaces, U.S. Energy Secretary Steven Chu directed all department offices to install cool roofs on any new buildings or when replacing old ones.