While India is awaiting a good monsoon this year after two consecutive years of deficient rains, the country may have to brace for more frequent drought years in the future, say meteorologists from from Pune and Kerala who have assessed country-wide rainfall data for more than 150 years.
According to the Indian Meteorological Department (IMD), if the rainfall during the four monsoon months of June to September is deficient by 10 per cent of its long-term average, it is declared a drought monsoon.
The latest findings suggest that while there have been alternate dry and wet spells over the past three decades, the frequency of drought years has been increasing. The period between 1950 and 89 had 10 drought years, followed by five more from 2000 onwards. The frequency is set to increase between 2020 and 2049, meteorologists say in a research paper to be published in Current Science, an Indian peer reviewed science journal published by Current Science Association along with the Indian Academy of Science.
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Meteorologists also say there is a need for further study to address this issue since the South Asian region is set to face severe drought spells for the next three decades. The constant cooling of the atmosphere over Central Asia has been cited as one of the main reasons for frequent drought years in the country that affect agriculture, power generation and the overall economy of the country.
According to the study, during 1870-1900s, there were very few droughts, followed by droughts once in three years during 1900-1930 and once in 15 years during 1930-1950. There were 10 drought years during 1950-1990. Since 2000, there have been five drought years: 2002, 2004, 2009, 2014, 2015. The frequency is expected to increase with rapid cooling of the atmosphere in Central Asia, says P V Joseph, senior meteorologist and lead scientist of the research paper.
“… The frequency and severity of droughts during 2020-49 is likely to be higher,” states the paper written by Joseph, who is group head at the Monsoon, Ocean Variability and Climate Change Studies at Nansen Environmental Research Centre in Kerala along with G Bindu and B Preethi from Pune’s Indian Institute of Tropical Meteorology (IITM).
While it is well known that green gases cause global warming, rapid cooling of the atmosphere points to the large discharge of sulphate aerosols from the industries as one of its causes. “There is a need to study the occurrence of frequent drought years which occurred during 1950-90 and has started again from 2002 onwards and whether they point out to the frequent discharge of sulphate aerosols?”says Joseph.