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El Niño

Topics Covered:

  1. Important Geophysical phenomena such as earthquakes, Tsunami, Volcanic activity, cyclone etc., geographical features and their location- changes in critical geographical features (including water-bodies and ice-caps) and in flora and fauna and the effects of such changes.


El Niño


What to study?

For Prelims and Mains: ENSO- El Nino and La Nia- causes, effects and impacts, global climate change and ENSO cycle.


Context: In a new study, researchers have found that because of climate change, extreme El Niño events are likely to become more frequent.


Key findings:

  • There is a shift in El Niño behaviour since the late 1970s.
  • All events beginning in the eastern Pacific occurred prior to that time, while all events originating in the western-central Pacific happened since then.
  • Therefore, climate change effects have shifted the El Niño onset location from the eastern Pacific to the western Pacific, and caused more frequent extreme El Niño events.


What is El Nino?

El Nino is a climatic cycle characterised by high air pressure in the Western Pacific and low air pressure in the eastern.

During this event, there is a warming of the sea surface temperature in the eastern and central equatorial Pacific Ocean.

It is one phase of an alternating cycle known as El Niño Southern Oscillation (ENSO).


What causes El Nino?

El Nino sets in when there is anomaly in the pattern.

  1. The westward-blowing trade winds weaken along the Equator and due to changes in air pressure, the surface water moves eastwards to the coast of northern South America.
  2. The central and eastern Pacific regions warm up for over six months and result in an El Nino condition.



  1. The temperature of the water could rise up to 10 degrees Fahrenheit above normal.
  2. Warmer surface waters increase precipitation and bring above-normal rainfall in South America, and droughts to Indonesia and Australia.
  3. Favours eastern Pacific hurricanes and tropical storms. Record and unusual rainfall in Peru, Chile and Ecuador are linked to the climate pattern.
  4. Reduces upwelling of cold water, decreasing the uplift of nutrients from the bottom of the ocean. This affects marine life and sea birds. The fishing industry is also affected.
  5. A recent WHO report on the health consequences of El Nino forecasts a rise in vector-borne diseases, including those spread by mosquitoes, in Central and South America. Cycles of malaria in India are also linked to El Nino.


Sources: Indian Express.