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GS Paper: GS1-14.Important Geophysical phenomena such as earthquakes, Tsunami, Volcanic activity, cyclone etc.,

  • WMO warns of ‘very’ strong El Nino, to last until February 2027

    WMO warns of ‘very’ strong El Nino, to last until February 2027

    Why in the News

    The World Meteorological Organization (WMO) has warned of an impending very strong El Nino that is expected to strengthen and last until February 2027. Its Secretary General stated that El Nino is firmly established and has the potential to deliver a massive blow to communities and economies across the world.

    How does El Nino work?

    1. The mechanism: El Nino is a periodic warming of sea surface temperatures in the equatorial and eastern Pacific Ocean, caused by a weakening of the trade winds.
    2. Why it travels: The warming moves the region where heat and moisture rise into the atmosphere, which alters temperature and rainfall patterns far from the Pacific.
    3. Its rhythm: The phenomenon recurs every two to seven years and a single event lasts up to about twelve months.
    4. What it produces: It is known to trigger heatwaves, wet spells and extreme temperatures.

    How strong is this event, and how is that graded?

    1. The index used: Intensity is determined by the sea surface temperature averaged over three months in the Nino 3.4 region along the equatorial Pacific Ocean.
    2. The readings so far: The index surpassed 1.5 degrees Celsius above normal during May to July and crossed 2 degrees Celsius above normal in July.
    3. The persistence forecast: The likelihood of El Nino continuing through February 2027 is put at close to 100 percent, the first time the agency has forecast an event at that degree of certainty.
    4. A possible record: Exceptionally warm Pacific temperatures make this potentially the strongest El Nino since monitoring began.

    What does it mean for India this season?

    1. The monsoon largely escaped: The India Meteorological Department (IMD) confirmed that rainfall in the later half of August came under the influence of the developing El Nino. With three fourths of the season over, the monsoon has largely escaped it.
    2. A countervailing signal: A positive phase of the Indian Ocean Dipole is expected to develop during September to November, with a seasonal mean value of 0.9 degrees Celsius.
    3. Why the offset matters: A positive Dipole strengthens rainfall over the Indian region and can therefore work against El Nino’s drying influence.
    4. The offset is not assured: The Dipole swung briefly towards the positive phase in late August and then returned to neutral.

    What is the WMO doing about it?

    1. A mobilisation without precedent in the agency: The Secretary General described this as the largest mobilisation with National Meteorological and Hydrological Services in the WMO’s fifty year history.
    2. Why those agencies: National meteorological services are the bodies that convert a global seasonal outlook into forecasts and warnings people can act on.
    3. Impacts are already visible: Droughts and floods are already causing disruption, and the agency expects these to intensify as the event strengthens.
    4. The recent record: Europe recorded one of its hottest summers in recent decades this year, and August brought record temperatures in many parts of the globe.

    Challenges to acting on an El Nino warning

    1. A seasonal outlook is not a local forecast: El Nino shifts the odds of dry conditions across a season and cannot say what a particular district receives in a particular week. Eg. The 2023 monsoon closed about 6 percent below normal for India as a whole, and several subdivisions still recorded surplus rain.
      The Fix: Issue impact based forecasts at district level that translate the seasonal outlook into expected effects on sowing dates, reservoir filling and power demand.
    2. The Indian Ocean modifies the Pacific signal: El Nino’s effect on the Indian monsoon depends on the state of the Indian Ocean, so an El Nino year is not automatically a drought year. Eg. The 1997 event was among the strongest recorded and the Indian monsoon that year was normal.
      The Fix: Publish the El Nino and Dipole outlooks as one combined regional signal rather than as two separate advisories a user has to reconcile.
    3. Warnings stop short of the last mile: Early warning coverage remains uneven for small farmers and fishing communities who cannot act on a technical bulletin. Eg. The United Nations Early Warnings for All initiative exists because a large share of the world’s population is still not covered by any early warning system.
      The Fix: Route advisories through State agriculture extension and fisheries departments in local languages, tied to one specific recommended action.
    4. Reservoirs are operated on inflows, not on forecasts: Storage decisions respond to water already received, so a deficit is managed only after it has appeared. Eg. Southern region reservoirs stood far below their ten year average through the summer of 2024, after the previous year’s deficient monsoon.
      The Fix: Write seasonal forecasts into reservoir rule curves so storage is conserved in advance of a forecast dry season.
    5. The consequences outlast the monsoon: El Nino affects the rabi season and global crops, so the exposure continues well after the Indian monsoon withdraws. Eg. India restricted rice exports during the 2023 El Nino year on domestic supply concerns.
      The Fix: Set buffer stock and import cover decisions against the forecast horizon rather than against the harvest just completed.

    Conclusion

    The forecast has settled the question of whether the event arrives and left open only what is done before it peaks. India’s monsoon has escaped this season, so the exposure shifts to the rabi crop, to reservoir storage and to the summer that follows. The marker to watch is whether the Indian Ocean Dipole holds its positive phase long enough to blunt the Pacific signal over the region.

    Back2Basics: Indian Ocean Dipole

    1. What it is: The Indian Ocean Dipole is the difference in sea surface temperature between the western and the eastern parts of the tropical Indian Ocean.
    2. Positive phase: The western Indian Ocean is warmer than the eastern part near Indonesia, which favours stronger rainfall over the Indian subcontinent and East Africa.
    3. Negative phase: The eastern part is warmer, which suppresses rainfall over India and shifts it towards Indonesia and Australia.
    4. How it is tracked: It is measured as the Dipole Mode Index, the temperature gradient between the two poles of the ocean.

    [2017] 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 characterized 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 Nino’s impact on the monsoon.

    Select the correct answer using the code given below:

    (a) 1 only

    (b) 2 only

    (c) Both 1 and 2

    (d) Neither 1 nor 2

  • Monsoon revives but El Nino threatens the rabi crop

    Why in the News

    The southwest monsoon has revived, cutting the seasonal deficit to 11.5%, but warns that a possible El Nino threatens the rabi crop and keeps urea supply in focus.

    What is El Nino?

    1. Definition: El Nino is the abnormal warming of the central and eastern Pacific that weakens the Indian monsoon and disrupts rainfall.
    2. Crop link: A weak or erratic monsoon reduces soil moisture and reservoir storage needed for the winter rabi crop.

    Why does the rabi outlook matter?

    1. Food and prices: Wheat and other rabi crops shape food inflation and buffer stocks.
    2. Input dependence: Adequate urea and irrigation are needed to protect rabi output if rainfall falters.
    3. Recovery is partial: A narrowed deficit does not remove the risk that late-season El Nino conditions bring.

    Conclusion

    A recovering monsoon eases the kharif outlook but leaves rabi exposed to El Nino. The next milestone is confirmation of El Nino conditions before the rabi season.

    PYQ Relevance

    [UPSC 2015]How far do you agree that the behavior of the Indian monsoon has been changing due to humanizing landscapes? Discuss.

    Linkage: The PYQ explores changing monsoon behaviour and its impact on Indian agriculture. El Niño-induced rainfall variability shows how climatic and human factors can alter monsoon patterns and crop outcomes.

  • Landslides: The Need for Early Warning Systems

    Why in the News?

    Recent landslides across the Western Ghats and other parts of India have revived the debate on installing early warning systems (EWS) for landslides. The renewed discussion exposes a gap between what landslide-prediction technology has already proven capable of and the absence of any single, scaled system deploying it nationally.

    Why has landslide prediction returned to the policy conversation, and does the science actually work?

    1. Trigger: Recent landslides in the Western Ghats and other parts of India reignited discussion on installing EWS for such events.
    2. Proven feasibility: Landslides can be predicted in high-risk zones. The 2024 Wayanad landslide killed more than 300 people, illustrating the human cost when prediction is absent.
    3. Working precedent: Two weeks before the Wayanad disaster, landslides in Munnar caused no fatalities. The Idukki district administration evacuated residents on the advice of an Amrita University research team, led by Maneesha Vinodini Ramesh, that was testing an EWS.
    4. Global validation: EWS already operates effectively in multiple countries, establishing that the underlying approach is proven rather than experimental.

    What are the two competing methodologies India is currently developing for landslide early warning?

    1. Amrita University approach: Deploys a network of on-site sensors, tilt meters, pressure gauges, accelerometers, at high-risk slopes to measure vibration and ground movement.
    2. Threshold-based alerts: When sensor readings cross well-defined thresholds, an automated warning is issued, allowing the administration to act.
    3. IIT Mandi approach: Professor Dericks Praise Shukla’s team uses probabilistic forecasting instead of physical sensors, currently being validated against ongoing landslide events in the Himalayan region.
    4. Satellite-based mapping: The IIT Mandi team has mapped vulnerable spots across the Himalayan region using a satellite-based database of past landslide events.
    5. Multi-factor modelling: The probabilistic model factors in localised rainfall forecasts along with soil conditions, rock stability, extent of slope, and population density.

    Why does neither current methodology, on its own, deliver a complete early warning solution?

    1. Sensor method’s blind spot: Amrita’s sensor network reports data only for the specific slope where instruments are installed. Neighbouring slopes remain unmonitored, even though landslides are highly localised events.
    2. Rainfall model’s lead-time constraint: Shukla’s probabilistic model depends on rainfall forecasts, but highly localised forecasts are currently available only for the day of the event or one day earlier, giving very little lead time.
    3. Trade-off exposed: The sensor method provides adequate lead time but incomplete geographic coverage. The probabilistic method provides wider coverage but insufficient lead time.
    4. Scale limitation: Both methods remain validated only at pilot or regional scale. Neither is currently integrated into a single nationwide operational system.

    What must change before India moves from pilot-scale projects to a comprehensive national system?

    1. Precondition 1: high-risk zone identification: A comprehensive system first requires identifying high-risk areas where landslides are frequent, before sensors or models can be meaningfully deployed at scale.
    2. Risk zones already flagged: Shukla identifies the north-western Himalayan region and parts of Manipur and Mizoram as highly vulnerable. Sikkim is relatively less vulnerable due to a less dense road network, which implies greater slope stability.
    3. Precondition 2: higher-resolution rainfall forecasting: The probabilistic method’s lead-time limitation can only be resolved once the India Meteorological Department develops higher-resolution rainfall forecasts, which is currently in progress.
    4. Timeline and resourcing: A comprehensive and effective landslide EWS can be built in about two years if resources and effort are properly dedicated to it, according to Shukla.
    5. Sequencing: The stated roadmap identifies high-risk zones nationally first, and installs sensors at selected sites only afterward, mapping precedes instrumentation, not the reverse.

    Conclusion

    Landslide early warning technology is scientifically proven and has already prevented casualties in India, as seen in Munnar in 2024. No standardised national system exists, however; current efforts are split between a sensor-based method and a rainfall-probability-based method, each constrained by a different limitation, localised coverage in one case, short lead time in the other. Scaling to a comprehensive national system depends on two preconditions currently absent: systematic identification of high-risk zones across India, and higher-resolution rainfall forecasting infrastructure from the India Meteorological Department. Until both are in place, early warning capability will remain confined to isolated pilot projects rather than a nationwide shield.

    PYQ Relevance

    [UPSC 2021] Describe the various causes and the effects of landslides. Mention the important components of the National Landslide Risk Management Strategy.

    Linkage: The PYQ examines India’s institutional approach to landslide risk reduction through the National Landslide Risk Management Strategy (NLRMS) and disaster preparedness. The article directly complements this PYQ by highlighting early warning systems, sensor networks, vulnerability mapping, localized rainfall forecasting, and timely evacuation, all of which are core components of proactive landslide risk management envisaged under the NLRMS.

  • Behind Europe’s heatwave, cliamte change the culprit

    Why in the News?

    A World Weather Attribution (WWA) study has confirmed climate change as the unequivocal cause of the ongoing European heatwave, which has broken or is forecast to break historic heat-stress records in 45% of 854 cities analysed. The finding sharpens a wider gap between the certainty climate science now offers and the declining political priority accorded to climate action.

    What does the WWA study establish about the causal role of climate change in the current heatwave?

    1. Unequivocal attribution: WWA found climate change, not the El Niño phenomenon or any other factor, responsible for the European heatwave.
    2. Recurrence pattern: This is the third severe heatwave to grip Europe in five years, after 2022 and 2023.
    3. Mortality scale: More than 1,300 excess deaths have been recorded since 21 June; over 1,00,000 people are estimated to have died from extreme heat across 2022 and 2023.
    4. Probability shift: Record-breaking night-time highs are nearly 100 times more likely now than in 2003; daytime peak temperatures are nearly 10 times more likely.
    5. Historical baseline broken: Temperature records being broken were set in 1976; the current daytime and overnight highs would have been virtually impossible to occur as recently as 1976.
    6. ENSO ruled out: The El Niño Southern Oscillation phase played no role in driving the heat during this spell.

    Why has climate attribution science become central to fixing responsibility for extreme weather events?

    1. Definition: Climate attribution is the scientific discipline that determines how much human-caused global warming influences the probability and intensity of specific extreme weather events. It quantifies how much worse or more likely a particular flood, heatwave, or drought has become compared to a hypothetical world without human-driven emissions
    2. Function: Attribution science tests the likelihood of a specific extreme weather event occurring if climate change were not taking place.
    3. Recency: The discipline has developed only over the last two decades.
    4. Speed gain: Assessments earlier took months or years; WWA’s methods now produce findings within days, even while an event is still ongoing.
    5. Purpose: The science removes ambiguity and fixes the exact extent of climate change’s responsibility for an event.
    6. Scientific caution without it: Scientists are otherwise wary of linking any individual extreme weather event to climate change without a dedicated attribution study.
    7. Policy intent: Beyond generating evidence, attribution studies are designed to force policymakers to act faster on climate change.

    Does scientific certainty on climate attribution translate into proportionate political action?

    1. Evidence-action gap: Scientific evidence on climate change is already voluminous and compelling, yet climate change has dropped down the list of global priorities.
    2. Political trigger: The decline has sharpened particularly after Donald Trump took office as US President.
    3. Forum evidence: Recent G7 meetings have carried little or no climate-related agenda or outcomes.
    4. Reversal of salience: Climate change was earlier among the most prominent items at international meetings involving influential leaders; this prominence has receded.
    5. Target abandonment: Scientists maintain the Paris Agreement targets of containing global temperature rise within 1.5°C to 2°C remain achievable, but governments treat them as effectively out of reach.
    6. Reframing of feasibility: Governments are treating the required resource mobilisation as politically impractical rather than scientifically unattainable.

    What risk does the global shift from mitigation to adaptation pose?

    1. Strategic shift: Countries are increasingly choosing to let climate change play out and to adapt to its impacts rather than prevent it.
    2. Scientific objection: Scientists routinely warn against adaptation as a substitute for mitigation.
    3. Inherent limits: Adaptation has limits beyond which impacts cannot be absorbed.
    4. Trend trajectory: Events such as the European heatwave are projected to increase in both frequency and intensity over coming years.
    5. Displacement, not resolution: The shift to adaptation transfers the climate risk from prevention to adaptation capacity rather than resolving it.

    Conclusion

    Climate attribution science has removed the scientific ambiguity once used to avoid linking individual extreme weather events to climate change. The European heatwave attribution exposes a widening gap between scientific certainty and political will, as global climate governance deprioritises mitigation. Countries are substituting adaptation for prevention despite scientists’ warnings that adaptation carries inherent limits. Closing this evidence-action gap is now central to achieving the Paris Agreement targets.

    PYQ Relevance

    [UPSC 2017] ‘Climate Change’ is a global problem. How India will be affected by climate change? How Himalayan and coastal states of India will be affected by climate change?

    Linkage: The PYQ xamines the impacts of climate change and the need for mitigation and adaptation strategies. The article uses the European heatwave as scientific evidence that climate change is intensifying extreme weather events and highlights the growing gap between climate science and political action.

  • Venezuela Earthquake

    Why in News?

    A powerful doublet earthquake (Magnitude 7.2 followed by 7.5) struck Venezuela, killing over 188 people and injuring more than 1,500. It is the strongest earthquake to hit Venezuela in 126 years.

    Key Highlights

    • Two major earthquakes struck within one minute, making it a doublet earthquake.
    • Epicentres were located west of Caracas, near the coastal town of Morón.
    • Tremors were felt in Colombia and Brazil.
    • The earthquakes occurred at shallow depths (10 km and 22 km), resulting in severe ground shaking.
    • International humanitarian assistance was offered by India, the United States, the United Nations, China, Brazil, and others.

    Why Did the Earthquake Occur?

    • Plate Boundary: Venezuela lies along the boundary between the Caribbean Plate and the South American Plate.
    • Strike-slip Faulting: The Caribbean Plate moves eastward relative to the South American Plate, causing horizontal movement along faults.
    • Active Fault Zone: The earthquake occurred near the El Pilar Fault System, one of the most active fault systems in northern Venezuela.
    • Shallow-focus Earthquake: Shallow earthquakes release energy close to the Earth’s surface, leading to greater destruction.
    • Doublet Earthquake: Two large earthquakes occurring almost simultaneously amplify structural damage.

    Prelims Pointers

    • Earthquake: Sudden release of energy in the Earth’s crust due to movement along faults.
    • Focus (Hypocentre): Point inside the Earth where an earthquake originates.
    • Epicentre: Point on the Earth’s surface directly above the focus.
    • Shallow-focus earthquakes: Depth less than 70 km; generally cause maximum damage.
    • Strike-slip fault: Fault where two blocks move horizontally past each other.
    • Doublet earthquake: Two major earthquakes of similar magnitude occurring close together in time and location.

    [2023] Consider the following statements :
    1. In a seismograph, P waves are recorded earlier than S waves.
    2. In P waves, the individual particles vibrate to and fro in the direction of wave propagation whereas in S waves, the particles vibrate up and down at right angles to the direction of wave propagation.
    Which of the statements given above is/are correct?

    [A] 1 only

    [B] 2 only

    [C] Both 1 and 2

    [D] Neither 1 nor 2

  • The recent cyclone on the east coast of India was called “Phailin”. How are the tropical cyclones named across the world?

  • Bring out the causes for more frequent landslides in the Himalayas than in Western Ghats

  • Tropical cyclones are largely confined to South China Sea, Bay of Bengal and Gulf of Mexico. Why?

  • The Himalayas are highly prone to landslides. Discuss the causes and suggest suitable measures of mitigation.

  • Mention the global occurrence of volcanic eruptions in 2021 and their impact on regional environment. (150 words) 2021 में घटित ज्वालामुखी विस्फोटों की वैश्विक घटनाओं का उल्लेख करते हुए क्षेत्रीय पर्यावरण पर उनके द्वारा पड़े प्रभाव को बताइए। (150 शब्दों में उत्तर दीजिए)