Air pollution distracts monsoons
Increasing air pollution above and at the edges of the Indian subcontinent and the regionally different heating of the Indian Ocean are changing the flow conditions in the earth's atmosphere. This leads to higher precipitation in the Sahel and a weaker monsoon influence in India.
The strong release of aerosols, climate change and the resulting warming of the Indian Ocean are closely related according to research by Chul Eddy Chung and Veerabhadran Ramanathan from the University of California in San Diego. The dense smog over the subcontinent and the adjoining areas of the northern Indian Ocean reduces solar radiation - by seven percent compared to 1930 to 2000 - and thus reduces the heating of the water. In contrast, the southern section of the sea heats up significantly more due to the increasing greenhouse effect and the unhindered solar radiation there from air pollution.
As a result, the monsoon wind systems are shifting to more southern latitudes and are only reaching India in a weaker form: since 1950, the corresponding monsoonal precipitation amounts in the region have decreased by five to eight percent on an annual average. On the other hand, more rain falls due to the changed air currents in parts of the Sahel zone. And even over the Indian Ocean, there is now greater amounts of precipitation than just a few decades ago.
But it's not just this spatial shift in monsoon precipitation that is causing the scientists concern. They also warn against a greater variability of the system: In years with less air pollution, India could experience significantly higher precipitation with the corresponding consequences, while, conversely, even greater aerosol pollution can trigger a significant lack of rain.