By Sid Perkins
A substantial part of the long-term warming seen in Europe during recent decades is the result of a decline in the region’s pollution and fog, a new study suggests.
Aerosols — tiny particles or droplets suspended in the atmosphere, such as fog, smoke and various pollutants — scatter light and cut down on visibility. But aerosols also scatter incoming radiation from the sun back into space, thereby cooling the atmosphere just above the ground level, says Pascal Yiou, an atmospheric scientist at the Laboratory of Climate Sciences and the Environment in Gif-sur-Yvette, France. Yiou and his colleagues recently studied the link between aerosols and cooling by analyzing temperature and daytime visibility data gathered at 342 weather stations throughout Europe from the late 1970s through 2006.
During those three decades, visibility has improved substantially, the researchers report online January 18 in Nature Geoscience. In part, the air is clear because of pollution control measures.
For example, today Europe experiences, on average, about nine fewer days with visibility of two kilometers or less during fall and winter months than it did three decades ago. In spring and summer, the continent’s weather stations see, on average, three fewer days with visibility two kilometers or less. Each decline is about 50 percent over the three-decade interval, Yiou notes.