Looming El-Nino threatens monsoon in India

2019 has been termed an El-Nino year, and the impact of this abnormal ocean warming phenomenon on the Indian monsoon makes for grim reading. The six years identified as El-Nino years this century have seen an average shortfall of 14% in the South-Western Monsoon rainfall (June to September) as compared to normal years.

While large parts of the country are reeling under heat-wave conditions, the sluggish progress of the South-Western Monsoon, the lifeline for farmers throughout the country, is alarming. According to the India Meteorological Department, June ended with a 33% deficit in monsoon rainfall.

While a host of meteorological factors have contributed to the sluggish monsoon, one of the most significant remains the prevalence of the El-Nino Southern Oscillation (ENSO). The ENSO is an abnormal warming of the tropical Pacific Ocean that disrupts global atmospheric circulation, which, in turn, influences temperature and precipitation across the globe.

With the ENSO phenomenon being observed since the beginning of 2019, there are fears that this might lead to a deficient monsoon. Various scientific studies have linked the prevalence of ENSO to a weak monsoon.

Although a direct correlation between the two has not been established, rainfall data from 2000 onwards shows that monsoon rainfall is heavily impacted in the El-Nino years. In five of these six El-Nino years, the monsoon rainfall was lower than the long-term average by 12% to 23%.

This shortfall is observed not only in aggregate but also across regions. The India Meteorological Department divides the country into 36 sub-divisions. In all El-Nino years since 2000, at least a quarter of 36 IMD sub-divisions have received deficient rainfall, with 2009 (22 deficient sub-divisions) and 2002 (21 deficient sub-divisions) being particularly bad.

A further breakdown of this data at the district level shows that regional and temporal variations appear to be increasing, even in a normal monsoon year. For example, in 2017, at an all-India level, monsoon rains amounted to 95% of the 50-year average. But in each of the four monsoon months (June to September), the percentage of districts that received normal rainfall (-19% to 19% deviation over their 50-year average) was less than a third. Deficient rainfall in June is devastating for farmers in large reaches of the country who have sown in expectation of rains. Unless there is a sharp revival of the monsoon, there will be a further blow to the already stressed Indian farmer, as well as a decline in agricultural productivity.

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First Published: Jul 03, 2019 07:09 IST