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Effects of global warming on El Niño in the 21st Century

Topics Covered:

  1. Conservation related issues.

 

Effects of global warming on El Niño in the 21st Century

 

What to study?

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

 

Context: A study, published in Journal nature, has thrown some light on the effects of global warming on El Niño in the 21st Century.

 

Highlights of the study:

As per the study, though the theater of action for El Niño is the tropical Pacific Ocean, its global reach costs the global community tens of billion dollars each time. El Niño may impact weather phenomenon across the world. For Eg: The eagerly-awaited winter rain and snow storms over California did not occur over California during the latest extreme El Niño.

The study notes that strong El Niño’s and thus extreme weather events associated with such strong El Niño’s will increase in the coming decades. This should serve as a warning to the countries on all continents that suffer from these extreme weather events.

However, available data is not sufficient to say with confidence how the tropical Pacific has responded to global warming till now. It is unclear if the impact of global warming on El Niño can easily be extracted considering its intrinsic tendencies and the fact that it depends on so many factors that are not easily predictable.

In this context, it is imperative that models be held to very stringent standards on their performance of El Niño behaviour during historic periods, especially the 20th century, as a test of their reliability for future projections.

This would also be necessary for projecting other events such as droughts and floods. For example, droughts over India are closely tied with El Niño and any projections of how droughts will respond to global warming will depend on how models perform in their historic depiction of El Niños as well as monsoons and how reliably they can project El Niño response to global warming in addition to how the models perform in reproducing floods to and droughts of 20th century.

 

Need of the hour:

Develop strong and accurate models to study El Niño and effects of global warming on it. This would also be necessary for projecting other events such as droughts and floods.

 

What is ENSO?

ENSO is nothing but El Nino Southern Oscillation. As the name suggests, it is an irregular periodic variation of wind and sea surface temperature that occurs over the tropical eastern Pacific Ocean. ENSO affects the tropics (the regions surrounding the equator) and the subtropics (the regions adjacent to or bordering the tropics). The warming phase of ENSO is called El Nino, while the cooling phase is known as La Nina.

 

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. In normal conditions, strong trade winds travel from east to west across the tropical Pacific, pushing the warm surface waters towards the western Pacific. The surface temperature could witness an increase of 8 degrees Celsius in Asian waters. At the same time, cooler waters rise up towards the surface in the eastern Pacific on the coasts of Ecuador, Peru, and Chile. This process called upwelling aids in the development of a rich ecosystem.

 

What causes El Nino?

El Nino sets in when there is anomaly in the pattern. 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. The central and eastern Pacific regions warm up for over six months and result in an El Nino condition. The temperature of the water could rise up to 10 degrees Fahrenheit above normal. Warmer surface waters increase precipitation and bring above-normal rainfall in South America, and droughts to Indonesia and Australia.

 

What are El Nino’s effects?

  1. El Nino affects global weather. It favours eastern Pacific hurricanes and tropical storms. Record and unusual rainfall in Peru, Chile and Ecuador are linked to the climate pattern.
  2. El Nino 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.
  3. Drought caused by El Nino can be widespread, affecting southern Africa, India, Southeast Asia, Australia, and the Pacific Islands. Countries dependent on agriculture are affected.
  4. Australia and Southeast Asia get hotter.
  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: down to earth.

Mains Question: El Nino and La Nina are opposite phases of what is known as the El Niño-Southern Oscillation (ENSO) cycle. Explain.