Opinion
From El Niño to La Niña: Is respite finally in sight?
Summary
- After a sweltering summer, recent downpours hinted of a sudden flip of this Pacific see-saw. Climate change is also at work, though, so India’s rainfall picture is getting more complex.
The scorching summer that India just trudged past was yet another reminder of a rapidly warming Earth, with temperatures soaring to almost 50° Celsius in one of our longest heatwave spells. The country logged more than 40,000 suspected cases of heatstroke, with a death toll of over 100 people.
But 2024 stands out for another reason: a shift in the Pacific Ocean’s see-saw of warm and cool water along the equator, a phenomenon that distorts weather around the globe. An El Niño phase that began in mid-2023 gave Asia drier weather than usual, with weak rains witnessed in the early part of the monsoon.
By end-May 2024, however, the India Meteorological Department (IMD) noted that this Pacific oscillation had turned neutral, and now it forecasts the likely development of its other extreme, La Niña, towards the end of August. The US National Oceanic and Atmospheric Administration has put a number to it.
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It predicts a 66% chance of La Niña emerging during September to November. The way this year’s monsoon roared back this month from sparse to plentiful, though, makes one wonder if the awaited tilt has already occurred.
Under the sun’s glare, oceanic water is always warm close to the surface around the equator, but the eastern end of an ocean can still be cooler than the other (and vice-versa). Under usual conditions, the Pacific’s warm water moves east slowly along with the planet’s rotation. But equatorial trade winds can blow it west.
In a neutral scenario, these forces balance each other. If trade winds weaken, which happens periodically, then the Earth’s spin prevails and the ocean’s warm water slops towards the Americas, leaving a great bulk of water on the Asian side cooler—and with less cloud formation and thus relatively dry. That’s El Niño.
Should those winds gain force, though, the warmth gets blown Asia’s way instead, causing lower air pressure, more evaporation and heavier rainfall in our part of the world. This is La Niña.
Something similar happens in the Indian Ocean, whose ‘dipole,’ which measures the heat gap between its east and west, must also be kept track of. It’s more complex, but also seen to make less of a difference.
An August IMD press release states that it found the dipole neutral, a reading it expects will endure through the monsoon season. The IMD’s map of cumulative rainfall from 1 June to 14 August shows that most of India got either normal or excess rain after El Niño ended.
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Our recent downpours may have been on account of the vacuum effect of an expansive low-pressure zone created by a scorching summer, rather than a sudden shift in the Pacific see-saw. So, has climate change become the dominant cause of warped weather?
Maybe it always was the bigger factor. The 2021 report of the UN Intergovernmental Panel on Climate Change was “virtually certain" that global warming would impact ocean conditions this century. With “medium confidence," it also held that El Niño and La Niña will gain in frequency.
Only 10 instances have been recorded of a flip within a year since 1950, but its rarity seems in decline. Since Indian rainfall gets affected, complex interactions could make projections of farm output, food prices and overall inflation less reliable.
Our rain-deficit anxiety has been washed away even before the start of La Niña, which now looks likely to aid the rabi crop. Thank warped weather for small mercies.
