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Why is the Indian Ocean Dipole in the news | Explained

admin — Wed, 01 Jul 2026 05:19:00 +0000

A woman walks along the promenade on a rainy monsoon day, at Marine Drive in Mumbai. File
| Photo Credit: PTI

In the monsoon of 1997, the Central Pacific was running one of the fiercest fevers in its recorded history in the form of an El Niño so violent that, by every rule of thumb, India ought to have stared at one of its worst droughts. However, in the greatest of meteorological surprises, June-September monsoon rainfall ended up being surplus, about 2% above normal. The Director-General of the India Meteorological Department (IMD), Mrutyunjay Mohapatra, observes that it has “happened only once ever.” The agent of that escape sat not in the Pacific but in India’s backyard sea and is called the Indian Ocean Dipole (IOD). With a ‘Super El Niño’ forecast for this year, it is an open meteorological question if a 1997 situation could recur. Currently, the monsoon is running a 40% deficit in India, with the IMD expecting June-September rain to be 90% — a tad above ‘deficient’ –of the long-period average.

What exactly is the IOD?

The equatorial oceans and the air directly above them are two layers in endless conversation, forever trading moisture. Where the sea surface is warm, it breathes water vapour upward; the moist air rises, cools, condenses into clouds, and falls back as rain. Where the surface is cool, the air sinks dry, and the sky withholds. The Pacific runs the largest version of this engine. Trade winds drag sun-warmed water and heap it near Indonesia, where the air ascends in towering rain, drifts back east at altitude, and subsides over the cool eastern Pacific off South America.

This is a vast east–west loop called the Walker circulation, whose rising western limb helps pump moist air towards South Asia. Every few years, the loop wobbles. This is the El Niño–Southern Oscillation (ENSO): in an El Niño, the central and eastern Pacific warm, the trade winds slacken, and the column of rising air slides eastward, leaving cool air to settle over the Indian Ocean and starve the monsoon; La Niña tilts it the other way and feeds the rains.

The Indian Ocean keeps a smaller engine of its own. Imagine it as a long, shallow bathtub of warm water with a slow seesaw running its length, called the IOD. In a positive phase, the western end of Africa warms while the eastern end, off Sumatra, cools; air rises over the warm western water, clouds gather, and the winds that feed the monsoon are given a westward shove towards the subcontinent. In a negative phase, the seesaw tips the other way and the rains are starved at the source. A neutral phase, as is likely this year, leaves the tub level and the monsoon to its own devices. These three phases are the dipole’s whole repertoire, and it cycles through them every year, El Niño or no El Niño.

When was this discovered and by whom?

Unlike the ENSO, the dipole is a young discovery. In 1999, a team led by N.H. Saji, with the Indian scientists B.N. Goswami and P.N. Vinayachandran among them, described it for the first time in Nature, showing that this east–west seesaw accounted for roughly an eighth of all temperature variability in the Indian Ocean and ran on its own engine, independent of the ENSO in the Pacific. Nevertheless, they engage in a complicated tango.

An El Niño often coaxes a positive dipole into being even as it throttles the monsoon, which is why 1997 could host both at once. The question that matters for India’s monsoon this year is whether the IOD can counter El Niño. “The El Niño,” Mohapatra puts it, “is like the big brother, and the IOD cannot fully compensate.” Only when the dipole turns strongly positive does its convergence over the Bay of Bengal cancel the subsidence that El Niño imposes, as it did in 1997. In most El Niño years, it stays quiet, and six monsoons in ten arrive depleted.

There is a third, faster hand on the scales. The Madden–Julian Oscillation — a pulse of cloud and rain that Roland Madden and Paul Julian identified in 1971, conventionally tracked through eight phases as it marches eastward across the tropics every 30-60 days and ignites over the equatorial Indian Ocean — governs the monsoon’s intraseasonal rhythm of active and break spells, and can itself nudge the dipole into life. The dipole is measured, meanwhile, by the Dipole Mode Index: the difference in sea-surface temperature anomaly between the western and south-eastern reaches of the basin, reckoned positive when the west runs warm.

Will the dipole come to monsoon’s rescue this year?

With the present evidence, no. The IMD’s models, and most others, forecast a neutral dipole across the four monsoon months; the Australian Bureau of Meteorology allows a slim chance of a positive turn late in the season, in August or September. But a level seesaw lends the rains nothing, and a positive phase arriving that late and that faintly would be too weak to blunt an El Niño.

Published – July 01, 2026 10:38 am IST

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Australian weather bureau sees 50% chance of La Nina this year

admin — Tue, 14 May 2024 09:24:35 +0000

A La Nina would have significant consequences for global agriculture because it typically brings wetter weather to eastern Australia and southeast Asia and drier conditions to the Americas.
| Photo Credit: Ritu Raj Konwar/The Hindu

There are early signs that a La Nina weather event may form in the Pacific Ocean later this year, Australia’s weather bureau said on Tuesday.

A La Nina would have significant consequences for global agriculture because it typically brings wetter weather to eastern Australia and southeast Asia and drier conditions to the Americas.

The bureau said it had declared a “La Nina Watch”.

“When La Nina Watch criteria have been met in the past, a La Nina event has subsequently developed around 50% of the time,” it said.

Also Read | El Niño, La Niña and changing weather patterns

La Nina events result from cooler sea surface temperatures in the Pacific. Warmer sea surface temperatures can cause an opposite weather phenomenon called El Nino, which occurred last year and lasted into early 2024.

“Sea surface temperatures in the central Pacific have been steadily cooling since December 2023,” the bureau said.

“The Bureau’s modelling suggests that ENSO will likely remain neutral until at least July 2024,” it said, using the formal name, the El Niño Southern Oscillation, that describes the switch between the two phases.

Japan’s weather bureau has said there is a 90% chance that the El Nino phenomenon will dissipate by the end of May.

Other forecasters have also heralded a La Nina later this year. Last week, Japan’s weather bureau said there was a 60% chance it would occur by November, and a U.S. government forecaster said there was a 69% chance that it would develop during July-September.

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As El Niño starts flip to La Niña, Latin America asked to be on alert

admin — Fri, 19 Apr 2024 07:30:20 +0000

Pea plants are damaged by drought, due to the El Nino weather phenomenon in Madrid municipality near Bogota, Colombia, January 17, 2016.
| Photo Credit: Reuters

Latin American nations must be on high alert as the weather phenomenon known as El Nino rapidly switches over to La Nina, experts said on Thursday, leaving populations and crops little time to recover.

El Nino and its abundant rains could soon turn into droughts caused by La Nina as well as an intense hurricane season across South America, experts said at a panel organized by the United Nations’ Food and Agriculture Organization (FAO).

The full weather pattern involving El Nino, La Nina and a neutral phase typically lasts between two to seven years. But experts said that the transition period from El Nino to La Nina is getting shorter.

“We just saw it happen,” said Yolanda Gonzalez, director of the International Research Center for the El Nino Phenomenon. “A year ago we came out of a Nina, and in March there were already signs of a Nino.”

“Now in March, April there are signs of a Nina,” she added. “We haven’t been able to recover from the impact.”

In South America, the weather patterns can hit key crops such as wheat and corn, denting commodity-dependent economies.

The phenomenon is not caused by climate change, FAO’s technical team told Reuters, but experts have seen that the effects of the weather pattern, such as rainfall, heat waves and drought, have become more extreme.

The rapid transitions between El Nino and La Nina could also be correlated with climate change, FAO said, though scientists have yet to establish definitive causation.

“These abrupt changes, and the fact that these cycles are now almost overlapping, ultimately decreases the ability to adapt to the changes,” said Marion Khamis, FAO’s regional risk management specialist. “This implies a huge challenge.”

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World experienced warmest February on record in 2024: European Union climate agency

admin — Thu, 07 Mar 2024 07:43:33 +0000

The Copernicus Climate Change Service said that every month since June last year has been the warmest such month on record.
| Photo Credit: AP

The world, last month, experienced the warmest February on record, with the average temperature being 1.77 degrees Celsius more than the February average for 1850-1900, the designated pre-industrial reference period, the European Union’s climate agency said on March 7.

The Copernicus Climate Change Service (C3S) also said that every month since June last year has been the warmest such month on record.

Scientists attribute the exceptional warming to the combined effects of El Nino — a period of abnormal warming of surface waters in the central Pacific Ocean — and human-caused climate change.

C3S last month said the global mean temperature breached the 1.5-degree Celsius threshold for an entire year for the first time in January. A permanent breach of the 1.5-degree Celsius limit specified in the Paris Agreement, however, refers to long-term warming over many years.

Explained | How El Nino could impact the world’s weather in 2023-24

According to climate scientists, countries need to limit the global average temperature rise to 1.5 degrees Celsius above the pre-industrial period to avoid the worst impacts of climate change.

Earth’s global surface temperature has already increased by around 1.1 degrees Celsius compared with the average in 1850-1900 — a level that has not been witnessed since 1,25,000 years, before the most recent ice age.

This warming is considered the reason behind record droughts, wildfires and floods worldwide. With an average temperature of 13.54 degrees Celsius, February 2024 was 0.12 degrees Celsius warmer than the previous warmest February in 2016, the EU’s climate agency said.

“The month was 1.77 degrees Celsius warmer than an estimate of the February average for 1850-1900, the designated pre-industrial reference period,” C3S said in an update.

The global average temperature for the last 12 months (March 2023–February 2024) is the highest on record, at 0.68 degrees Celsius above the 1991-2020 average and 1.56 degrees Celsius above the 1850-1900 pre-industrial average.

“The daily global average temperature was exceptionally high during the first half of the month, reaching two degrees Celsius above the 1850-1900 levels on four consecutive days (February 8–11),” C3S scientists said.

The average global sea surface temperature (SST) for February 2024 was 21.06 degrees Celsius, the highest for any month in the dataset. The previous high was in August 2023 (20.98 degrees Celsius).

C3S director Carlo Buontempo said, “February joins the long streak of records of the last few months. As remarkable as this might appear, it is not really surprising as the continuous warming of the climate system inevitably leads to new temperature extremes.

“The climate responds to the actual concentrations of greenhouse gases in the atmosphere so, unless we manage to stabilise those, we will inevitably face new global temperature records and their consequences,” Mr. Buontempo said.

The World Meteorological Organization on Tuesday said the 2023-24 El Nino has peaked as one of the five strongest on record and will continue to impact global climate in the coming months despite a weakening trend.

The United Nations agency also said above-normal temperatures are predicted over almost all land areas between March and May. The WMO said there is about a 60% chance of El Nino persisting during March-May and an 80% likelihood of neutral conditions (neither El Nino nor La Nina) from April to June.

There is a chance of La Nina developing later in the year, but those odds are currently uncertain, it said. Scientists closely tracking the development in India have said La Nina conditions setting in by June-August could mean monsoon rains would be better this year than in 2023.

El Nino — a periodic warming of the ocean surface in the central and eastern tropical Pacific Ocean — occurs every two to seven years on average and typically lasts nine to 12 months.

It is associated with increased rainfall in the Horn of Africa and the southern U.S., and unusually dry and warm conditions in Southeast Asia, Australia and southern Africa.

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