The 2020-2021 La Niña event has ended and neutral conditions (neither El Niño nor La Niña) are now likely to prevail over the tropical Pacific in the next few months, the World Meteorological Organization (WMO) said on Tuesday.
In India, this would mean conditions are favourable for a normal monsoon and normal temperatures. “We generally associate neutral ENSO conditions with a normal monsoon in India. Most ENSO neutral years have brought us normal monsoon in past years,” explained M Mohapatra, director general, IMD. Earlier on Tuesday, IMD in its second stage long range monsoon forecast said the country is likely to be normal at 101% of long period average.
El Niño and the Southern Oscillation (ENSO) is a periodic fluctuation in sea surface temperature and the air pressure of the overlying atmosphere across the equatorial Pacific Ocean according to the National Oceanic and Atmospheric Administration (NOAA).
ENSO has a major influence on weather and climate patterns such as heavy rains, floods and drought. El Niño has a warming influence on global temperatures, whilst La Niña has the opposite effect. In India for example, El Nino is associated with drought or weak monsoon while La Niña is associated with strong monsoon and above average rains and colder winters.
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Air temperatures globally are expected to be above average between June and August, especially in the northern hemisphere, WMO said in its statement. There is a 78% chance of neutral conditions in the tropical Pacific until July, decreasing to 55% by August-October, and with more uncertainty for the rest of the calendar year, according to WMO’s El Niño/La Niña Update.
“La Niña has a temporary global cooling effect, which is typically strongest in the second year of the event. This means that 2021 has got off to a relatively cool start – by recent standards. This should not lull us into a false sense of security that there is a pause in climate change,” said WMO secretary-general Petteri Taalas.
“Carbon dioxide concentrations remain at record high levels and so will continue to drive global warming. According to new predictions issued by WMO, there is a 90% likelihood of at least one year between 2021-2025 becoming the warmest on record. This would dislodge 2016 – a strong El Niño year – from the top ranking,” added Taalas.
The end of La Niña and widespread above average sea-surface temperatures because of global warming mean that air temperatures over land are forecast to be warmer than average from June to August 2021 over almost the whole northern hemisphere, in particular over the central western part of North America, the far northern part of Asia, part of central Asia, and far eastern Asia, the Arabian Peninsula and the northern Caribbean. Exception to recording above normal temperatures is likely in north-western Europe, south Asia, and the northern part of South America, extending into the southern Caribbean, according to the Global Seasonal Climate Update. This also means India may record moderate temperatures during the ENSO neutral phase.