Will there be an El Niño in 2023 and what are the implications?

By contrast, the preceding five years from 2014 to 2018 – roughly coinciding with the first term of the Narendra Modi government – registered an average annual rainfall of just 1,072.1 mm and 812.4 mm during the southwest monsoon.

The surplus precipitation – more than the “normal” or historical long period annual average of 1,160.1 mm and 868.6 mm for the monsoon season – during the last four years has helped deliver higher agricultural growth, relative to the previous period that recorded poor rain in three (2014, 2015 and 2018) out of the five years (see the table below).

According to the national accounts data, the farm sector has grown by an average of 4.3% per year during 2019-20 to 2022-23 (the Modi government’s second term), as against 3.2% during 2014-15 to 2018-19.

The La Niña bounty

The bountiful rainfall during 2019-22 has been significantly attributed to La Niña – an atmospheric wind and sea surface temperature (SST) variability phenomenon occurring over the equatorial Pacific, but causing worldwide weather disruptions.

La Niña basically refers to an abnormal cooling of the central and eastern Pacific Ocean waters off the coasts of Ecuador and Peru. Such cooling (SSTs falling 0.5 degrees Celsius or more below a 30-year average for at least five successive three-month periods) is a result of strong trade winds blowing west along the equator, taking warm water from South America towards Asia. The warming of the western equatorial Pacific, then, leads to increased evaporation and concentrated cloud-formation activity around that region, whose effects may percolate to India as well.

The latest La Niña event was one of the longest ever, lasting from July-September 2020 to December-February 2022-23. And it brought copious rains to India – just as two previous “strong” La Niñas in 2007-08 and 2010-11, followed by one “moderate” episode in 2011-12, had done.

The most recent Oceanic Niño Index or ONI value — a three-month running-average SST deviation from the normal in the east-central equatorial Pacific — was minus 0.4 degrees Celsius for January-March 2023. Since La Niña is characterised by a negative ONI exceeding or equal to minus 0.5 degrees, it means that the so-called ENSO (El Niño-Southern Oscillation) cycle has entered a “neutral” phase.

The El Niño threat

While La Niña is associated with good rainfall in India, this isn’t the case with El Niño – the opposite “warm” phase of ENSO. During El Niño, the trade winds weaken or even reverse: Instead of blowing from east (South America) to west (Indonesia), they could turn into westerlies. As the winds blow from the west to east, they cause the masses of warm water to move into the central and eastern equatorial Pacific Ocean. The rise in SSTs there, thus, produces increased rainfall along western Latin America, the Caribbean and US Gulf Coast, while depriving Southeast Asia, Australia and India of convective currents.

The ENSO cycle, as already pointed out, is currently in the “neutral” state. According to the US National Oceanic and Atmospheric Administration’s most recent update, ENSO-neutral conditions are likely to “persist through the Northern Hemisphere early summer [of] 2023”. In other words, at least till June. However, “a transition to El Niño is favoured by July-September 2023”, with its chances “increasing through the fall (September-November)”.

The Australian Bureau of Meteorology, too, has forecast “a 50% chance that an El Niño may develop later in 2023”. This is “about twice the normal likelihood”, the agency has said in its March 28 report, adding that “warmer than average SSTs have [already] emerged in parts of the eastern tropical Pacific in recent weeks”. The India Meteorological Department is scheduled to issue its first long-range forecast of rainfall for the 2023 southwest monsoon on Tuesday.

The implications

Most global models are seeing the transition from ENSO-neutral to El Niño happening this year. But that would probably affect the monsoon only in the second half (August-September) of the season. Will it translate into deficient rainfall – after four-in-a-row surplus years – and, by extension, low or even negative agriculture growth?

The table below shows that practically all drought years in India since Independence – marked by large declines in foodgrain production or monsoon failures – have witnessed El Niño events of varying intensity. The sole exception was 1966-67, although the year before had recorded a “strong” El Niño (To elaborate, mean SSTs have to be at least 0.5 degrees Celsius higher than the average for a minimum of five overlapping three-month periods to qualify as an El Niño event. The positive ONI values or SST deviations have to be 1.5-1.9 degrees for categorisation as “strong”, above 2 degrees for “very strong”, 1-1.4 degrees for “moderate” and 0.5-0.9 degrees for “weak”).

While all drought years have invariably been El Niño years, the reverse doesn’t hold true though. Another table below gives a list of all the El Niño years that weren’t bad agriculture years. The best examples are 1982-83 and 1997-98. Foodgrain output fell only marginally in these two “very strong” El Niño years. Agricultural GDP growth was similarly positive in 1951-52, 1963-64, 1968-69 and 1994-95; all of them saw “moderate” El Niño events.

To sum up, 2023 could well end the run of good rainfall years since 2019. The statistical probability of that is high, whether or not there is an El Niño. Moreover, El Niño itself can turn out to be “weak”.

Either way, everyone – from policymakers to tractor companies that have posted all-time-high sales in the past four years – has to brace themselves for a not-too-great monsoon this time. And in an election year leading up to the national Lok Sabha polls in April-May 2024, the attendant political challenges would be no less daunting.