NEW DELHI: The impact of climate change over the monsoon in India has been clearly evident in terms of erratic rainfall patterns. However, a new study shows that climate change could trigger an increased frequency of dust storms in the Middle East, which is likely to enhance rainfall in India during the monsoon season.
The study led by researchers at Indian Institute of Technology, Bhubaneswar (IIT-B) shows that dust emitted from the Middle Eastern deserts transported to the Arabian Sea could enhance rainfall over South Asia, especially during severe drought episodes over the Indian region.
Desert dust aerosols emitted from Arabian and North African deserts increase rainfall over India at short time scales of about a week or two. This is made possible due to the warming induced by this dust over the Arabian Sea, which acts as a source of energy to speed up the monsoon circulation (winds, moisture) towards the Indian region. This relationship is now stronger during drought years associated with El-Nino.
“India has faced droughts or large-scale deficits and changes in the spatial pattern of monsoon rainfall due to ongoing climate change. However, with global warming in place and changing wind patterns, we can expect a rise in dust storms across Middle Eastern deserts in the coming years. This dust may get transported to the Arabian Sea under favourable conditions and trigger short heavy rain spells over the Indian region,” said Dr V Vinoj, Assistant Professor, School of Earth Ocean and Climate Sciences, Indian Institute of Technology Bhubaneswar.
The author said nature compensates for the deficit created by human activities. It is well established that anthropogenic factors reduce rainfall and continue to do so for long-timescale (decades). Still, the silver lining is that there is a short period of respite to this drying trend in the form of increased short-time (about a week or so) rainfall.
“With the increasing potential of El-Nino like conditions in the future, this dust induced effects will become increasingly important in understanding changing characteristics of rainfall over India,” said Vinoj.
The researchers drew attention to this critical observation and pointed to the need for tracking dust storms and their emissions to understand their effect on monsoon rainfall and even on air quality which is another growing problem for India.
According to the study, normally, while ascertaining the air pollution levels on regional scales, we look at PM 2.5, which comprises many different elements, with dust being the most dominant one over India. However, recent studies have shown a decline in the desert dust over India due to increased pre-monsoon rains over the Northwestern parts of India, potentially due to the regional effect of climate change.
However, human activities with associated emissions will continue to rise due to the country's economic development. In addition, increased dust over the Middle Eastern deserts transported over the Arabian Sea increases short period rainfall over India. So, on the one hand, dust emitted over India is declining, whereas dust over the Arabian Sea is rising, which will lead to increased rainfall.