Decline in Hazy WeatherHas Contributed to Warming in Europe

A sharp decline in air pollution in Europe has led to a “massive decline” in fog, haze, and mist, which in turn has contributed to significant temperature increases in the past three decades, according to a new report. Using data from 342 continental weather stations, Robert Vautard of France’s Atomic Energy Commission and other researchers determined that the number of “low-visibility” events in Europe — defined as visibility under 8 kilometers (5 miles) — has dropped by 50 percent since the 1970s. Smog and haze cool the surface of the earth by blocking sunlight, and the decline in the pall of pollution has contributed to 10 to 20 percent of the . 5 C (.9 F) warming that Europe has experienced since the 1970s, according to the report in the journal Nature Geoscience. The new research highlights a phenomenon known as “global brightening,” in which skies over Europe, the U.S., and other industrialized regions have cleared as pollution has decreased. Thirty years ago, smog may have masked the extent to which greenhouse gases were warming the planet, and cleaner skies will mean higher temperatures, researchers say.