New Delhi: The onset of an El Nino is almost certain now, with a high probability that it will set in this very month, the World Meteorological Organisation (WMO) has said in its latest update, released Wednesday.
In its first forecast since March, the WMO has indicated that there was “about 60% chance for the onset of El Nino during May-July, rising to 70-80% during July- September period”. The full effect of the El Nino, after it sets in, will become apparent in 2024.
The WMO and other weather agencies had previously suggested that an El Nino could set in this year, but no specific information was shared before now.
The El Nino is likely to “fuel higher global temperatures”, impacting weather patterns across the world. In India, El Nino’s are associated with increased heat and drought, negatively impacting agriculture.
An El Nino is a naturally occurring climatic phenomenon that causes sea surface temperatures in the eastern and central Pacific Ocean to become warmer than usual, leading to increased rainfall over southern South America, southern United States, the Horn of Africa and central Asia. El Ninos, however, are also known to cause drought over South Asia, Southeast Asia, and Australia. A La Nina is when the opposite — cooling of sea surface temperatures with the opposite effect — happens.
El Ninos occur on average “every two to seven years, and episodes usually last nine to 12 months”, according to the WMO update.
At the moment, conditions of El Niño-Southern Oscillation (ENSO) are neutral, meaning neither a La Nina nor an El Nino is occurring. These neutral conditions are prevailing after the world experienced a ‘triple dip’ La Nina, which lasted three years between 2020 and early this year.
According to Wednesday’s WMO update, there is a 60 per cent chance of a transition from ENSO-neutral to El Niño during May-July 2023, which will increase to about 70 per cent in June-August and 80 per cent between July and September.
“We just had the eight warmest years on record, even though we had a cooling La Niña for the past three years and this acted as a temporary brake on global temperature increase. The development of an El Niño will most likely lead to a new spike in global heating and increase the chance of breaking temperature records,” said WMO Secretary-General Prof. Petteri Taalas in a statement.
Last year, the WMO had said there was a high chance that the years between 2022 and 2026 would be the hottest on record, with a chance that mean surface temperatures would temporarily cross 1.5 degrees Celsius above pre-industrial levels.
The world is already 1.1 degrees warmer than in pre-industrial times, and scientists estimate warming crossing 1.5 degrees will accelerate and worsen the effects of climate change.
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What this means for India
According to the WMO, there is no indication of the strength or the duration of the El Nino, and the forecast is still in its early stages as the ‘spring predictability barrier’ — a periodic phenomenon that hampers accurate forecasting — has not entirely passed.
Last month, the Indian Meteorological Department (IMD) predicted a “normal” monsoon over India, with rainfall within the 96-106 per cent range of the long-period average (LPA).
The LPA — calculated as average rainfall during the season over the country as a whole between 1971 and 2020 — is 87 centimetres.
The IMD defines LPA as average rainfall recorded over a particular region for a given interval (like month or season) over a period of 30 or 50 years. The LPA for the south-west monsoon across India is 87mm, based on the average rainfall over the 1961 -2010 period.
At a press conference last month, IMD director general Mritunjay Mohapatra had said that any effect the El Nino might have on the monsoon will be visible only during the second half of the season.
“It’s not necessary that an El Nino will lead to a bad monsoon. Of the 15 El Nino years from 1951 to 2022, there were six with normal to above normal rainfall,” Mohapatra had said during the press conference.
Other climate phenomena could also mitigate the El Nino’s effect, such as the Indian Ocean Dipole (IOD), which causes differences in sea surface temperatures in the Indian Ocean.
IMD’s climate models for the monsoon forecast a positive IOD development, which could counteract the negative effects of the El Nino.
Below-normal snow cover over the northern hemisphere could also help India’s monsoon, Mohapatra had said.
The IMD will issue an updated forecast in May, ahead of the onset of the southwest monsoon.
(Edited by Poulomi Banerjee)