Indian army soldiers evacuate people from flooded areas of a village in Hojai district, Assam on June 18, 2022. Photo: Reuters/Anuwar Hazarika
- The World Meteorological Organization believes it is quite possible that the current La Niña event is entering a third year – an extremely rare event.
- Researchers don’t yet have enough data to say whether climate change is causing stronger and longer La Niña periods or whether this extension is part of natural climate variability.
- For India, this could mean longer monsoons, prolonged heat waves and increased risk of flooding.
New Delhi: The World Meteorological Organization (WMO) says there is a strong chance that the ongoing La Niña event will continue until at least August and could even enter its third year , possibly signaling that such events could become more frequent due to climate change.
La Niña and its counterpart El Niño are natural 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 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 the ocean interact, reinforce each other and create a ‘feedback loop’ that 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 Office of Meteorology.
The WMO has stated that while there is a good chance that the current La Niña – which began in September 20202 – will continue until September this year, “some long-term forecasts even suggest that it could persist until 2023”. If that happened, it would only be the third “La Niña triple dip” (three consecutive winters in the northern hemisphere of La Niña conditions) since 1950.
La Niña events can cause flooding in Australia, Southeast Asia, and even India and cause droughts in the United States and East Africa. They can also cause the development of cyclones in the Pacific and Atlantic oceans.
According Nature Newsthe long La Niña period is “probably just a random event in the climate”, but some climatologists warn that climate change could make “La Niña-like conditions more likely in the future”.
“We are stacking the odds higher for these upcoming triple events,” Matthew England, a physical oceanographer at the University of New South Wales in Sydney, Australia, told the website.
The current La Niña is “strange” because, unlike previous triple dips, it did not come after a strong El Niño – during which ocean heat builds up and dissipates for a year or two. The dynamics behind the event are puzzling, said Michelle L’Heureux, a physicist with the US National Oceanic and Atmospheric Administration.
Effect of climate change?
Scientists have not yet concluded whether La Niña and El Niño events are becoming more frequent due to human-induced climate change or natural variations in global climate. write for The science of yarnRaghu Murtugudde said “many more years of data and reanalysis” are needed before full separation of the impact of global warming from natural climate variability can be achieved.
“Human-induced climate change is amplifying the impacts of natural events like La Niña and increasingly influencing our weather patterns, particularly through more intense heat and drought and the associated risk of wildfires – as well than record deluges of rainfall and flooding,” said WMO Secretary-General Petteri Taalas.
The latest report from the Intergovernmental Panel on Climate Change (IPCC) indicates that El Niño and La Niña events have become more frequent and stronger since 1950, but cannot say whether this is due to natural variability or to climate change.
According Nature News, while it is natural to expect more El Niño-like conditions because climate change is warming the oceans, observations over the past half-century have shown otherwise. He said “as the weather warmed, a tongue of rising water in the eastern equatorial Pacific Ocean remained cold, creating more La Niña-like conditions.”
England, the scientist, says the melting Greenland ice sheet is infusing cool, cold water, slowing the “dominant belt of ocean currents: the Atlantic Meridian Overturning Circulation (AMOC)”. According to Nature News, this would leave excess heat in the tropical South Atlantic, triggering a “series of atmospheric pressure changes that ultimately strengthen the Pacific trade winds”, which “push warm water westward, creating more of La Niña”. -similar conditions”.
What does this mean for India?
If La Niña conditions persist, India should expect a series of changes in its weather, climate and seasons. From prolonged heat waves to longer monsoons and floods, policymakers will face a series of events.
In late December 2021 and early January this year, the east coast of India received unexpected heavy rains. As The science of yarn reported then, these rains were an “abnormal event caused by a combination of several meteorological changes” – including La Niña.
Murtugudde said The science of yarn that if there was a drop in pressure from north India into the peninsula because of La Niña, there was a rush of humidity from the Bay of Bengal into Tamil Nadu – which ran into this pressure model. “And the pattern acted like a mountain by mixing the cold descending air with the warm, moist air coming from the hot bay. It’s a bizarre combination, which was made possible by the unusually strong easterly winds. , coming from the South China Sea,” he said.
If La Niña and El Niño events become stronger and more frequent, these “abnormal” events could also become more frequent.
Flooding in the northeast may 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 strengthened 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,” climatologist Roxy Mathew Koll told the magazine. “Atmospheric moisture volume increases with increasing temperature because warmer air holds more moisture and longer…Therefore, the large amount of precipitation we are currently seeing could impact the change climate,” he said.
In another report, Down to earth said the changing nature of La Niña is a “cause for great concern.” Although the phenomenon usually brings wet and cold winter and spring seasons for India, large parts of the country have not experienced spring at all this year.
“This happened as a north-south pressure pattern, which usually forms over India during the winter season and dissipates in the spring, continued through March and April this year. The pattern has interacted with hot waves coming from the rapidly warming Arctic region to trigger and prolong heat waves in the country,” the report said.