What Is El NINO?

2014 to 2016 witnessed one of the worst El Nino conditions. Catastrophic events such as drought and flood became common across the globe. 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.
To understand El Nino, let’s get to know 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.
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.

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.
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 caused by El Nino can be widespread, affecting southern Africa, India, Southeast Asia, Australia, and the Pacific Islands. Countries dependent on agriculture are affected.
Australia and Southeast Asia get hotter.
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.

The rise in sea surface temperature may be intensified by global warming. From the current study, we learn that El Nino can exacerbate global warming and hence the process could become a vicious circle.

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.

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.

Source:TH