Climate Change

An explainer on El Nino

The weather phenomenon is to affect agriculture, rainfall and other meteorological indicators from this year. A primer on what it actually is

By Manas Ranjan Senapati
Published: Friday 30 June 2023
Photo: iStock

The El Nino Southern Oscillation (ENSO) has been associated with altering the global climate, floods, droughts, devastating cyclones, and temporary temperature changes. El Nino and La Nina collectively refer to a major ocean-current, together called ENSO. 

This is associated with a band of warm water that develops in the central and east-central equatorial Pacific Ocean, and the Pacific coast of South America. 

El Nino occurs along with a change in air pressure above the tropical Pacific Ocean, called Southern Oscillation. Coastal waters then become warmer in the eastern tropical Pacific. The atmospheric pressure above the ocean decreases as a result. 

When the water warms, fish suddenly disappear. So fishermen in Peru were the first to notice the irregular cycles of rising ocean temperatures, as reported by The Pioneer. They named the phenomenon El Nino (little boy in Spanish) since it often occurs around the time of Christmas. They called the opposite process of the eastern tropical Pacific cooling, as La Nina (little girl). 

ENSO causes changes in temperature, climate and precipitation globally. It leads to floods, droughts, and tropical cyclones with devastating impacts. 

In South America, El Nino causes rain, while it brings droughts to Australia and Indonesia. These droughts dry the reservoirs and reduce rivers’ water, threatening the region’s water supply. Water availability for agriculture irrigation reduces as well. 

It is observed that developing countries dependent on their own fishing and agriculture, particularly those which border the Pacific Ocean, are most affected. 

First observed in 1986, advanced monitoring techniques have been able to note at least 26 El Nino events since 1900. Since 2000, El Nino events were in 2002-03, 2004-05, 2006-07, 2009-10, 2014-16, and 2019. 

The events of 1982-831997-98 and 2014-16 are among the strongest on record

In 1998, an El Nino event caused approximately 16 per cent of the world’s reef systems to die. This was an unusual incident when the event temporarily increased the air temperature by 1.5°C, rather than an increase of 0.25°C usually associated with El Nino.

El Nino has caused extreme weather and changes in Odisha’s climatological conditions. During an El Nino event, people in Odisha reportedly experienced sunstrokes in 1998 and a super cyclone in 1999. 

In the 2019 El Nino event, Odisha reported another super cyclone Fani which caused damages to a large area covering three districts (Puri, Khordha and Cuttack) of the state. Later that year, another cyclone Bulbul caused heavy rain and storms in Odisha. This caused damages to agriculture, uprooted trees, and tore down power lines in the state. The regular monsoon of the state was later intensified, causing large floods. 

Amphan, another super cyclonic storm, caused large-scale destruction to West Bengal and Odisha. El Nino 2014-16 brought enormous tropical cyclones Phailin and Hudhud to Odisha. 

The ENSO cycle causes extreme weather globally, and affects rainfall and air currents. These shifts correlate with new interactions among disease carriers, creating novel pathogens and incidents of epidemic diseases as explained by a report in Scientific American.  

The El Nino cycle is associated with increased risks of vector-borne diseases such as malaria, dengue, Zika virus and Rift Valley fever. In 2015-2016, El Nino triggered outbreaks globally.

Malaria outbreaks in India, Venezuela, Brazil, and Colombia have been traced to El Nino. Outbreaks of another mosquito-transmitted disease, Australian encephalitis, occurs in temperate south-east Australia after heavy rainfall and flooding caused by La Nina.

During the 1997-98 El Nino event, Rift Valley fever spread widely after extreme rainfall in north-eastern Kenya and southern Somalia. Incidents of Kawasaki disease in Japan and the west coast of the United States have been related to ENSO conditions through winds across the North Pacific Ocean. 

The Secretary-General of World Meteorological Organization Professor Petteri Taalas said earlier this year, “We just had the eight warmest years on record, even though we had a cooling La Nina for the past three years and this acted as a temporary brake on global temperature increase. The development of an El Nino will most likely lead to a new spike in global heating and increase the chance of breaking temperature records”.

In 2023, El Nino is predicted to impact the global climate further. The period for which it will last is still unknown. 

Views expressed are the author’s own and don’t necessarily reflect those of Down To Earth

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