Greenhouse gases cause concern, but scientists are more worried about particulates

While greenhouse gases, or GHGs, are causing concern about the long-term fate of the Indian monsoon, researchers now think aerosols from vehicular exhaust, half-burnt crop residue, dust and chemical effluents may be weakening the life-giving rainy season even more than GHGs.

An Indian Institute of Tropical Meteorology, Pune, team led by climatologist R. Krishnan studying the likely monsoon impact of GHGs over the next century has come to this conclusion.

In 2015, Mr. Krishnan reported in the journal Climate Dynamics that a mix of GHGs, aerosols and changes in forest and agricultural cover was affecting the strength of the monsoon, which was known to be weakening over the last 50 years. This result was based on mathematical modelling and computer simulation. The relative contribution of the individual factors, however, was not clear then. “New simulations suggest that aerosols may be a far more important factor than GHGs,” said Mr. Krishnan, who spoke at a meeting of the Indian Academy of Sciences in Bengaluru last week. He said aerosols were “the major cause of weakening of the monsoon.”

New modelling

The scientist and his team used an upgraded forecasting model that was used this year by the India Meteorological Department for forecasts. The model will help prepare India’s first home-grown forecast of climate change from global warming, and be part of Intergovernmental Panel on Climate Change reports.

Dust clouds shield the earth from the sun’s rays, depressing land and sea temperatures. The monsoon, which is produced by the difference in temperature between the two, is thus weakened.