Air pollution brings “global dimming”

Visibility on clear days has declined in much of the world since the 1970s because of an increase in airborne pollutants, Reuters reported. Scientists described a “global dimming”, in particular over south and east Asia, South America, Australia and Africa. Visibility improved over Europe, however, and remained relatively stable over North America.


Aerosols — tiny particles or liquid droplets expelled into the air by the burning of fossil fuels and other sources — are responsible for the dimming, the researchers said. In the journal Science, the American scientists said that soot, dust, sulfur dioxide particles and other aerosols all harmed visibility. Their data may shed light on the relationship between long-term changes in air pollution and climate change.


“Aerosols are going up over a lot of the world, especially Asia,” where industrial activity has increased, Robert Dickinson of the University of Texas, one of the researchers told Reuters. He and two University of Maryland researchers tracked measurements of visibility — the distance someone can see on clear days — taken from 1973 to 2007 at 3,250 meteorological stations worldwide.


The scientists used recent satellite data to confirm that the visibility measurements from the meteorological stations were a good indicator of aerosol concentrations in the air. Aerosols from burning coal, industrial processes and the burning of tropical forests can influence the climate and be a detriment to health, the researchers noted. Pollutants such as carbon dioxide and other greenhouse gases are transparent and do not affect visibility.


See full story