Current Affairs · · GS1 · Geography

Why a strong El Niño does not always mean a poor monsoon

India's 2026 monsoon ended about 13% below normal as a strong El Niño developed, the weakest since 2015. But El Niño does not always cause drought: in 1997, a very strong El Niño came with near-normal rain. A Hindu explainer shows how the Indian Ocean Dipole, the Madden-Julian Oscillation, where the Pacific warms and other factors shape the outcome.

Event date:

REq1
  1. Note1 / 7

    WHY IN NEWS?

    • India's 2026 southwest monsoon ended at about 87% of the long-period average (LPA), roughly 13% below normal — the weakest since 2015.
    • It came as a strong El Niño developed in the Pacific.
    • IMD reported that East and Northeast India had their driest monsoon since 1901.
    • Since 1950, seven monsoons have coincided with a moderate or strong El Niño. In five, including 2026, rainfall was at least 10% below the LPA, which IMD calls "deficient".
    • 2023 was below normal but not deficient, and 1997 was near-normal — prompting renewed study of what offsets El Niño.
  2. Note2 / 7

    HOW STRONG EL NIÑO YEARS COMPARE

    YearConditionsMonsoon outcome
    1997Very strong El Niño, favourable (positive) IODNear-normal rainfall
    2015Strong El Niño, weak IOD supportAbout 13–14% deficit
    2023El Niño, positive IODAbout 94% of LPA (below normal)
    2026Strong El Niño, largely neutral IODAbout 87% of LPA (deficient)

    A 2024 study in Atmospheric Research found that ENSO, the IOD and the MJO acting together explain these different outcomes.

    IMD's categories for all-India seasonal rainfall: deficient (below 90% of LPA), below normal (90–95%), normal (96–104%), above normal (105–110%) and excess (above 110%).

  3. Note3 / 7

    KEY FACTORS THAT MODIFY EL NIÑO (I)

    1. Indian Ocean Dipole (IOD)

    A positive IOD — a warmer western and cooler eastern Indian Ocean — boosts convection and moisture flow towards India. In 1997, it offset El Niño. A neutral or negative IOD offers no such support; 2015 saw a deficit of about 13%.

    1. Madden-Julian Oscillation (MJO)

    A band of clouds and rain that moves eastward around the tropics, recurring every 30–60 days. Its active phase over the Indian Ocean increases rain; its suppressed phase reduces it. In August 2023, the MJO sat over Africa and the Americas, and India's August rainfall was 36% below normal.

    1. Where the Pacific warms

    Eastern Pacific and central Pacific El Niños affect the atmosphere differently. In 1997, the warmth was concentrated near South America; central Pacific warming tends to suppress the Indian monsoon more. A 2006 study in Science showed the importance of warming location.

  4. Note4 / 7

    KEY FACTORS THAT MODIFY EL NIÑO (II)

    1. Southern Hemisphere circulation

    Changes in the Southern Annular Mode (SAM) and westerly winds affect Indian Ocean temperatures and IOD development. A 2024 study linked stronger southern Indian Ocean westerlies in 2015 to the failure of a favourable IOD.

    1. Regional weather systems

    Upper-air pressure patterns and moisture flows can make up for deficits. A 2026 study in Nature Communications linked the 1997 recovery to an unusual high-pressure system over the Iranian Plateau and extra moisture from the Arabian Sea.

    1. Other drivers
    • Tibetan Plateau heating shapes upper-level winds and the land–sea temperature contrast that drives the monsoon.
      • Eurasian snow cover changes how much the land heats up in spring.
      • Atlantic Niño — warming in the tropical Atlantic — alters tropical teleconnections.
      • Soil moisture and evapotranspiration influence local rainfall.
  5. Note5 / 7

    WHY FORECASTING IS HARD

    • Non-linear interactions: ENSO, the IOD and the MJO can strengthen or cancel each other. IMD increasingly uses multi-model forecasts to handle this.
    • Intra-seasonal swings: Active and break spells make rain uneven within a season, as in August 2023.
    • Regional differences: National totals hide local droughts, as East and Northeast India showed in 2026.
    • Climate change: A 2026 Nature Communications study projects that greenhouse warming will make the monsoon more sensitive to ENSO-linked droughts.
    • Model limits: Models still struggle to represent convection and ocean–atmosphere links accurately.
  6. Note6 / 7

    IMPLICATIONS FOR INDIA

    • Agriculture: A large share of farmland is rain-fed, so crops depend heavily on the monsoon.
    • Food security: Crop losses can push up food prices and hurt nutrition.
    • Water: Weak rain lowers reservoir storage and groundwater recharge.
    • Rural incomes: Lower farm income raises debt and dependence on rural employment schemes.
    • Disasters: Uneven rain can bring drought and floods in different regions at once.
  7. Note7 / 7

    WAY FORWARD

    These are the explainer's suggestions, not adopted policy.

    • Better forecasts: Combine ENSO, IOD, MJO, SAM and regional circulation in high-resolution models.
    • Better observation: Expand ocean buoys, satellites and automatic weather stations.
    • Climate-smart farming: Promote drought-resistant varieties, millets, crop diversification and micro-irrigation.
    • Water management: Scale up watershed development, rainwater harvesting and groundwater recharge.
    • Risk reduction: Strengthen crop insurance under PMFBY, agro-climate advisories and district-level early warning.

Sources

Syllabus

PaperSubjectSub-topic
GS1GeographyIndian monsoon, ocean–atmosphere interactions, climatology
GS3EnvironmentAgriculture, disaster management, climate change
PrelimsGeographyENSO, IOD, MJO, SAM, IMD rainfall categories

Topics

Agriculture GeographyClimatologyIndian Geography

Related previous-year questions

Asked in earlier UPSC Prelims papers on this topic. Answer, then check.

  1. UPSC Prelims 2017 · Geography · Indian Geography

    With reference to ‘Indian Ocean Dipole (IOD)’ sometimes mentioned in the news while forecasting Indian monsoon, which of the following statements is/are correct? 1. IOD phenomenon is characterised by a difference in sea surface temperature between tropical Western Indian Ocean and tropical Eastern Pacific Ocean. 2. An IOD phenomenon can influence an El Niño’s impact on the monsoon. Select the correct answer using the code given below:

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Show answer

    Answer: B. VERDICT: The answer is 2 only. An Indian Ocean Dipole event can influence El Nino's impact on the monsoon, but the temperature difference is within the Indian Ocean, not between it and the Pacific. ANALYSIS: Statement 1 is INCORRECT. The Dipole is an irregular oscillation of sea surface temperatures in which the western Indian Ocean becomes alternately warmer and then cooler than the eastern part of the same ocean. The statement wrongly places the second pole in the tropical eastern Pacific. Statement 2 is CORRECT. A positive Dipole can bring good rainfall to India even in an El Nino year, while a negative one can aggravate the El Nino effect, so it modulates that influence. SOURCE: Indian Express explainer on the Indian Ocean Dipole and the monsoon. Source type EM. HOW TO CRACK IT: The name contains the disproof, since Indian Ocean Dipole means two poles within the Indian Ocean, and a pole located in the Pacific would make it a different phenomenon altogether. Reading a scientific term as a description of its own geography is the quickest route here. Keep the Dipole and El Nino distinct but linked, because the examinable point is that the two interact rather than that either alone determines the monsoon.

    Difficulty: hard · statement

    Open this question on its own page, with the full explanation →

  2. UPSC Prelims 2011 · Geography · Climatology

    La Nina is suspected to have caused recent floods in Australia. How is La Nina different from El Nino? 1. La Nina is characterised by unusually cold ocean temperature in equatorial Indian Ocean whereas El Nino is characterised by unusually warm ocean temperature in the equatorial Pacific Ocean. 2. El Nino has adverse effect on south-west monsoon of India, but La Nina has no effect on monsoon climate. Which of the statements given above is/are correct?

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Show answer

    Answer: D. Correct Answer: Neither 1 nor 2 Both statements are incorrect because they wrongly describe the location and monsoon impact of El Niño and La Niña. Statement-wise Explanation 1. Statement 1 — Incorrect El Niño and La Niña do not occur in the Indian Ocean. They occur in the central and eastern equatorial Pacific Ocean. They are opposite phases of the El Niño-Southern Oscillation (ENSO). El Niño: abnormal warming of surface waters in the central/eastern equatorial Pacific. La Niña: abnormal cooling of surface waters in the central/eastern equatorial Pacific. 2. Statement 2 — Incorrect La Niña does affect the Indian monsoon. The statement saying it has “no effect” is wrong. El Niño generally weakens the South-West Monsoon and may cause deficient rainfall or drought-like conditions in India. La Niña generally strengthens the South-West Monsoon and may cause above-normal rainfall, floods, and intense rainfall events. Extra UPSC Info ENSO has three phases: El Niño, La Niña, and Neutral phase. El Niño is linked with weak trade winds, reduced upwelling near South America, and warmer Pacific waters. La Niña is linked with stronger trade winds, stronger upwelling, and cooler Pacific waters. ENSO influences rainfall, droughts, floods, agriculture, food prices, and disaster management in India. A separate phenomenon called the Indian Ocean Dipole (IOD) occurs in the Indian Ocean. A positive IOD can sometimes reduce the negative impact of El Niño on the Indian monsoon. Final Takeaway El Niño and La Niña occur in the Pacific Ocean, not the Indian Ocean. Both affect the Indian monsoon, with El Niño generally weakening it and La Niña generally strengthening it. Therefore, the correct answer is Neither 1 nor 2.

    Difficulty: medium · statement

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  3. UPSC Prelims 2020 · Geography · Oceanography

    With reference to Ocean Mean Temperature (OMT), which of the following statements is/are correct? 1. OMT is measured up to a depth of 26°C isotherm which is 129 meters in the south-western Indian Ocean during January–March. 2. OMT collected during January–March can be used in assessing whether the amount of rainfall in monsoon will be less or more than a certain long-term mean. Select the correct using the code given below:

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Show answer

    Answer: B. Statement 1 – INCORRECT: Ocean heat content (OHC) and Ocean Mean Temperature (OMT) are important climatic parameters required for atmospheric and oceanic studies like cyclone and monsoon predictions and ocean heat transport estimations. Sea surface temperature (SST) is routinely used for predicting whether the total amount of rainfall that India receives during the monsoon season will be less or more than the long-term mean. The SST is restricted to a few millimetres of the top ocean layer and is largely influenced by strong winds, evaporation, or thick clouds. In contrast, OMT, which is measured up to a depth of 26 degree C isotherm, is more stable and consistent. Statement 1's specific figure of '129 meters in the south-western Indian Ocean during January-March' cannot be verified as correct from the material. Hence statement 1 is not correct as stated. Statement 2 – CORRECT: Scientists from Pune's Indian Institute of Tropical Meteorology (IITM) find that ocean mean temperature (OMT) that has better ability to predict this than the sea surface temperature. Compared with SST which has 60% success rate of predicting the Indian summer monsoon, OMT has 80% success rate. OMT collected during January–March can thus be used in assessing whether the amount of rainfall in monsoon will be less or more than a certain long-term mean. Hence statement 2 is correct. Correct statement: 2 only → Option (b).

    Difficulty: hard · statement

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  4. UPSC Prelims 2026 · Geography · Indian Geography

    With reference to the climate of Andaman and Nicobar Islands, which of the following statements is/are correct? 1. The climate can be defined as a humid, tropical coastal climate. 2. It receives rainfall from both South-west monsoon and North-east monsoon. 3. Maximum precipitation is between December and May. Select the answer using the code given below:

    1. 1 only
    2. 1 and 2
    3. 2 and 3
    4. 3 only
    Show answer

    Answer: B. Statement 1 is correct: The islands have a tropical climate with warm summers and not so chill winters, which is described as a humid, tropical coastal climate. Statement 2 is correct: The Andaman and Nicobar Islands experience two monsoon phases. The Southwest Monsoon arrives in June, July, August and September, and the Northeast Monsoon arrives in October, November and December. During these periods the islands are blessed with heavy rainfall, which transforms the landscape into a lush, green wonderland. Statement 3 is not correct: Maximum precipitation is received during the Southwest Monsoon, not between December and May. Statements 1 and 2 are correct, so the answer is Option (b).

    Difficulty: easy · statement

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Practice questions

  1. A positive Indian Ocean Dipole means:

    1. A cooler western and warmer eastern Indian Ocean
    2. A warmer western and cooler eastern Indian Ocean
    3. Uniform warming across the Indian Ocean
    4. Warming only in the Bay of Bengal
    Show answer

    Answer: B. It usually supports the Indian monsoon.

    Difficulty: easy · statement

  2. The Madden-Julian Oscillation typically recurs every:

    1. 2–7 years
    2. 30–60 days
    3. 10–12 months
    4. 10–20 years
    Show answer

    Answer: B. ENSO cycles last 2–7 years.

    Difficulty: easy · statement

  3. According to IMD, seasonal monsoon rainfall below 90% of the long-period average is classified as:

    1. Below normal
    2. Deficient
    3. Normal
    4. Drought
    Show answer

    Answer: B. Below normal is 90–95% of LPA.

    Difficulty: easy · statement

Mains practice

Answer-writing practice on this article. Attempt it first, then open the hints.

  1. GS1 · 250 words

    "El Niño is a warning, not a verdict, for the Indian monsoon." Explain with reference to the roles of the IOD, MJO and other factors, and discuss implications for forecasting and agriculture.

    Show hints
    1. 1997 vs 2015 vs 2023 vs 2026
    2. IOD, MJO, El Niño location
    3. SAM, regional systems, forecasting limits
    4. rain-fed farming, adaptation