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La Niña Likely To Enter ‘Extremely Unlikely’ Third Year. What Must India Do?

La Niña Likely To Enter ‘Extremely Unlikely’ Third Year. What Must India Do?

Indian Army soldiers evacuate people from flooded areas at a village in Hojai district, Assam, June 18, 2022. Photo: Reuters/Anuwar Hazarika

  • The World Meteorological Organisation believes there is a strong possibility that the ongoing La Niña event could enter a third-year – an extremely rare event.
  • Researchers don’t have enough data yet to say if climate change is causing stronger and longer La Niña periods or if this prolongation is part of natural climate variability.
  • For India, this could mean longer monsoons, prolonged heatwaves and increased chances of flooding.

New Delhi: The World Meteorological Organisation (WMO) says there is a high chance that there is high probability that the ongoing La Niña event will continue until at least August and could even enter its third year and perhaps signalling that such events could become increasingly common due to climate change.

La Niña and its counterpart El Niño are naturally-occurring events. They occur every two to seven years, when the Pacific Ocean and the atmosphere above it change from their neutral (‘normal’) state. While El Niño events are associated with a warming of the central and eastern tropical Pacific (near the Americas), La Niña events cool these areas.

These changes in the Pacific Ocean and its overlying atmosphere occur in a cycle known as the El Niño–Southern Oscillation (ENSO). “The atmosphere and ocean interact, reinforcing each other and creating a ‘feedback loop’ which amplifies small changes in the state of the ocean into an ENSO event. When it is clear that the ocean and atmosphere are fully coupled an ENSO event is considered established,” according to the Australian government’s Bureau of Meteorology.

The WMO said that while there is a strong chance that the current La Niña – which started in September 2022 – will continue until September this year, “some long-lead predictions even suggest that it might persist into 2023”. If that happens, it would only be the third “triple-dip La Niña” (three consecutive northern hemisphere winters of La Niña conditions) since 1950.

La Niña events can cause flooding in Australia, Southeast Asia and even India and cause droughts in the US and East Africa. They can also cause more cyclones to develop in the Pacific and Atlantic oceans.

According to Nature News, the long La Niña is “probably just a random blip in the climate” but some climate researchers warn that climate change could make “La Niña-like conditions more likely in future”.

“We are stacking the odds higher for these triple events coming along,” Matthew England, a physical oceanographer at the University of New South Wales in Sydney, Australia, told the website.

The current La Niña is “weird” because, unlike previous triple dips, it hasn’t come after a strong El Niño – during which ocean heat builds up and dissipates over a year or two. The dynamics causing the event are puzzling, said Michelle L’Heureux, a physical scientist at the US National Oceanic and Atmospheric Administration.

Climate change effect?

Scientists have not yet concluded if La Niña and El Niño events are becoming more common because of human-induced climate change or naturally occurring variations in the global climate. Writing for The Wire Science, Raghu Murtugudde said that “many more years of data and reanalysis” are needed before the complete separation of the global warming impact from natural climate variability can be achieved.

“Human induced climate change amplifies the impacts of naturally occurring events like La Niña and is increasingly influencing our weather patterns, in particular through more intense heat and drought and the associated risk of wildfires – as well as record-breaking deluges of rainfall and flooding,” said WMO secretary-general Petteri Taalas.

The latest report by the Intergovernmental Panel on Climate Change (IPCC) said that El Niño and La Niña events have been more frequent and stronger since 1950 – but couldn’t say whether this was caused by natural variability or climate change.

According to Nature News, though it is natural to expect more El Niño-like conditions because climate change warms the oceans, observations over the past half-century have found the opposite. It said “as the climate has warmed, a tongue of upwelling waters in the eastern equatorial Pacific Ocean has stayed cold, creating more La Niña-like conditions”.

England, the scientist, says the melting of the Greenland ice sheet infuses fresh cold water, slowing down the “dominant conveyor belt of ocean currents: the Atlantic Meridional Overturning Circulation (AMOC)”. According to Nature News, this would leave an excess of heat in the tropical South Atlantic, triggering a “series of air-pressure changes that ultimately strengthen the Pacific trade winds”, which “push warm water to the west, thus creating more La Niña-like conditions”.

What does this mean for India?

If La Niña conditions persist, India should expect a range of changes in its weather, climate and seasons. From prolonged heatwaves to longer monsoons and floods, policymakers will have to contend with a range of events.

In late December 2021 and early January this year, India’s east coast received unexpectedly heavy rains. As The Wire Science reported then, these rains were an “anomalous event brought on by a combination of several weather changes” – including La Niña.

Murtugudde told The Wire Science that while there was a drop in pressure from North India into the peninsula because of La Niña, there was a rush of moisture from the Bay of Bengal into Tamil Nadu – which ran into this pressure pattern. “And the pattern acted like a mountain by mixing the cold air coming down with the warm moist air coming in from the warm bay. That’s a freak combination, which was made possible by the unusually strong winds from the east, coming all the way from the South China Sea,” he said.

If La Niña and El Niño events become stronger and more frequent, such “freak” events could also become more frequent.

The floods in the Northeast could also have been exacerbated by La Niña. A combination of La Nina in the Pacific and a negative Indian Ocean Dipole in the Indian Ocean has strengthened the southwesterly winds in the Bay of Bengal, according to Down To Earth.

“These strong monsoon winds in the Bay of Bengal can now carry much more moisture than ever before, in response to global warming,” Roxy Mathew Koll, a climate scientist told the magazine. “The volume of atmospheric moisture increases with rising temperature because warmer air holds more moisture and for longer… Hence, the large amount of rainfall that we see now might be a climate change impact,” he said.

In another report, Down To Earth said the changing character of La Niña is a “cause of great concern”. Though the phenomenon usually brings wet and cold winter and spring seasons for India, large parts of the country did not experience a spring season at all this year.

“This happened as a north-south pressure pattern, which usually forms over India during the winter season and dissipates by spring, continued into March and April this year. The pattern interacted with warm waves coming in from the rapidly warming Arctic region to initiate and prolong heatwaves in the country,” the report said.

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