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La Niña grip to weaken from Feb; expect warm spring and summer next year
The current La Niña has been relatively weak but unusually prolonged. It started in 2020 and returned for its third consecutive winter, making it a rare “triple-dip” event.
After three years of La Niña conditions continuously influencing the global weather conditions, the grip of La Nina is expected to weaken from spring of 2023, the National Oceanic and Atmospheric Administration (NOAA) of US has said. This could mean a relatively warm spring and summer over India, experts said.
The current La Niña has been relatively weak but unusually prolonged. It started in 2020 and returned for its third consecutive winter, making it a rare “triple-dip” event. Other triple-dip La Niña’s recorded since 1950 were between 1998-2001, 1973-1976, and 1954-1956. Interestingly, though La Niña is associated with cooler temperatures over the Indian sub-continent, 2022 saw an unusually warm spring and summer and now above normal day and night temperatures are being recorded during this winter over northwest India according to the India Meteorological Department.
There is a 76% chance of La Niña during the Northern Hemisphere winter (December-February) 2022-23, with a transition to ENSO-neutral favoured in February-April 2023 (57% chance), NOAA said on December 5.
“ENSO neutral condition basically means that there will be no forcing or impact from a global atmospheric phenomenon like La Niña or El Nino during the February to April period. Local factors and seasonal features will be dominant. Climate change has also impacted seasonal features which will be felt. The impact of western disturbances will be important in determining the weather during the spring of 2023. The WDs will determine the number of cloudy or rainy days. Overall, we can expect slightly above normal temperatures during spring and summer next year,” explained DS Pai, director of the Institute of Climate Change Studies and former climate scientist at IMD Pune.
“We should prepare for a harsher summer. Its too early to say anything about the monsoon. But some global models are indicating the establishment of El Nino conditions after spring which should worry us if those models are correct in their projections. The diminishing impact of La Nina for now would certainly mean warmer temperatures in spring and summer,” said M Rajeevan, climate scientist and former secretary, ministry of earth sciences. Rajeevan added that the impact of La Nina and El Nino are accentuated due to climate change. “Since the base temperature is going up, the impact of these global atmospheric phenomenon is accentuated leading to extremes in certain cases. During the last 4 to 5 years, the Horn of Africa is recording a severe drought. Moreover, this was an unusual La Nina when very high temperatures were recorded in several parts of the world including India.”
The global mean temperature in 2022 is currently estimated to 1.15°C (± 0.13°C) over pre-industrial levels. The past eight years are on track to be the eight warmest on record, fuelled by ever-rising greenhouse gas concentrations and accumulated heat. A rare triple-dip cooling La Niña may be making 2022 the fifth or sixth warmest. However, this does not reverse the long-term trend; it is only a matter of time until there is another warmest year on record, World Meteorological Organisation said in its provisional report on the State of Global Climate 2022 on November 6.
Meteorologists have linked the current La Niña to a variety of natural disasters, including drought and food security problems in the Horn of Africa, flooding in Australia, and drought in the US Southwest, NOAA said in a report on November 29.
El Nino refers to a warm phase of ENSO, which has a major influence on weather and climate patterns such as heavy rains, floods and drought. In India, El Nino is associated with drought or weak monsoon. La Niña is associated with strong monsoon and above average rains and colder winters.
La Nina has a cooling influence in India even as it recorded a very unusual spring and summer dominated by extreme record-breaking heat spells.
La Niña appears when easterly trade winds intensify the upwelling of cooler water from the depths of the eastern tropical Pacific, causing a large-scale cooling of the eastern and central Pacific Ocean surface near the equator according to NOAA. These strong trade winds also push the warm equatorial surface waters westward toward Asia and Australia. The cooling of the ocean’s surface layers during La Niña affects the atmosphere by modifying the moisture content across the Pacific. It alters global atmospheric circulation and can cause shifts in the path of mid-latitude jet streams in ways that intensify rain in some regions and bring drought to others.
“We are expecting La Niña conditions to continue till February. Even then, normal to above normal temperatures are likely over most of NW India and some parts of NE India. We will get a more accurate picture of post winter period in a few days,” said IMD director general M Mohapatra.
