“Pollution is drying up monsoon showers: Study” by India Today
September 30, 2011
The Indian summertime monsoon is drying up and manmade pollution is to blame for much of this change, a new study has concluded.
Averaged over the whole country, the summer rainfall has witnessed a reduction of four to five per cent over the past 50 years. Scientists have been debating if it was due to natural variations or human activities such as pollution and industrial activity.
Now a study by the Princeton University and the National Oceanic and Atmospheric Administration (NOAA) says that aerosols play a prominent role in shaping regional climate change over South Asia. Researchers used climate models to see how the Indian monsoon responds to natural and man-made factors.
“We find that the observed precipitation decrease can be attributed mainly to human influenced aerosol emissions”, Massimo Bollasina, who led the study said. “The drying is a robust outcome of a slowdown of the tropical meridional overturning circulation, which compensates for the aerosol induced energy imbalance between the northern and southern hemispheres.”
Aerosols are tiny air-borne particles which can come from several sources like volcanic ash, dust and sea salt.
They can also be created due to the burning of biomass and fossil fuels, emission of sulfates, nitrates and black carbon by power plants and automobiles. Earlier studies have linked increase of aerosols and with the so-called ‘dimming’ effect or decrease in surface solar radiation over the South Asian region.
The results suggest that anthropogenic or man-made aerosols have substantially masked the precipitation increase over the monsoon area that would have otherwise occurred purely due to increased greenhouse gases, researchers said.