Mains Paper 1: Geography | Salient features of World’s Physical Geography
From UPSC perspective, the following things are important:
Prelims level: El Nino, La Nino and ENSO
Mains level: Impact of El-Nino
- The UN said an El Nino event that could disrupt global weather is likely by the end of this year.
- The World Meteorological Organisation forecast a 70% chance of an El Nino developing by the end of this year.
- ENSO is nothing but El Nino Southern Oscillation.
- 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).
- This warming phase of ENSO is called El Nino, while the cooling phase is known as La Nina.
- An El Nino or La Nina episode lasts nine to 12 months. Some may prolong for years.
- Its average frequency is every 2 to 7 years. El Nino is more frequent than La Nina.
What characterizes El-Nino?
- El Nino is a climatic cycle characterized 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 are its causes?
- 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 and 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.
Effects of El-Nino
- El Nino favors eastern Pacific hurricanes and tropical storms. Record and unusual rainfall in Peru, Chile and Ecuador are linked to the climate pattern.
- 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.
- Drought and warming caused by El Nino can be widespread, affecting southern Africa, India, Southeast Asia, Australia, and the Pacific Islands.
- 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.
Why is it a concern?
- From the current study, we learn that El Nino can exacerbate global warming and hence the process could become a vicious circle.
- A recent study that analysed data collected by NASA’s satellite, found that the massive event resulted in the release of over 3 billion tonnes of carbon into the atmosphere.
- This in turn pushed the carbon-dioxide concentration in the atmosphere to record levels.
- La Nina is a climate pattern that describes the cooling of surface ocean waters along the tropical west coast of South America. It is considered to have the opposite effect of El Nino.
- It brings greater than normal rainfall in Southeast Asia and Australia, and causes drier-than-normal conditions in South America and the Gulf Coast of the United States.
- La Nina events sometimes follow El Nino events.