Monsoons that frequently hit Asia have created a pathway for black carbon, nitrogen oxides and other harmful pollution to get into the stratosphere, according to findings reported yesterday in the journal Science.
Once pollution reaches the stratosphere, it circles the globe for several years before falling back to the lower atmosphere or disintegrating. The researchers from the University of Waterloo and the U.S. National Center for Atmospheric Research warn that such pollution can alter the composition of the stratosphere and affect the ozone layer.
“The monsoon influence on the stratosphere is expected to become increasingly important given the ongoing growth of Asian emissions, with large continued increases over the next decades expected for SO2 (sulfur dioxide) and NOx (nitric oxides),” the report says.
The study is based on measurements from a satellite, part of the Atmospheric Chemistry Experiment from the Canadian Space Agency. The instrument is so sensitive that it can detect parts per billion of hydrogen cyanide, a pollutant generated by fire and plentiful over Asia. Measurements between 2004 and 2009 show an increase in hydrogen cyanide in the stratosphere during the monsoons, which create a vortex over Asia in the summers.
The study’s authors say more time is needed to research the impact of the pathway, but they add that the pathway can alter the makeup of other gases in the stratosphere, like water vapor, and it can affect how much solar heat reaches the planet (Margaret Munro, Canwest News Service, March 25). – JP