First recognized by Peruvian fishermen due to the appearance of unusually warm water along the coast of Peru, El Nino is a weather phenomenon that causes significant shifts in global weather patterns. In Spanish, El Nino translates to ‘The Little Boy’, a term coined by Spanish immigrants. It represents the warmer phase of the El Nino Southern Oscillation (ENSO) phenomenon.
During an El Nino phase, regions around the world, including India, observe generally warmer temperatures and lesser rainfall. Sea Surface Temperatures in the equatorial Pacific Ocean off the northern coast of South America during this phase are at least 0.5 degrees Celsius higher than average. Strong El Nino events such as the one that occurred in 2015-2016 witnessed temperature anomalies as high as 3°C.
Interestingly, El Nino events follow no regular cycle and occur irregularly at two- to seven-year intervals. These events coincide with the Southern Oscillation, which represents a shift in air pressure over the tropical Pacific Ocean.
Predicted El Nino in May 2023
Several climate models have forecasted an El Nino event for May 2023. Following the conclusion of a record three-year La Nina in March 2023, the equatorial Pacific Ocean has returned to normal temperatures, known as the neutral phase.
Impact on India
The upcoming El Nino event is set to weaken the southwest monsoon season, which is responsible for nearly 70% of India’s total rainfall. Farmers heavily depend on these monsoons, and a disruption to this pattern could drastically affect agriculture in the region.
Sub-seasonal factors such as the Madden-Julian Oscillation (MJO) and monsoon low-pressure systems may partially alleviate the effects by enhancing rainfall in certain areas. However, El Nino can trigger heatwaves and droughts in India and other regions globally. It could also bring extreme rainfall and flooding to regions, including California in the United States, leading to widespread damage to coral reefs.
Global Warming Concerns
El Nino events contribute to rising global average temperatures. The 2023 El Nino could push global temperatures towards 1.5°C above preindustrial averages.
This is particularly concerning as ocean heat content is already at record levels according to the World Meteorological Organization (WMO). Past events have had grave consequences; for instance, the 2015-2016 El Nino resulted in widespread heatwaves in India, causing approximately 2,500 deaths each year.
Past Instances of El Nino
Historically, El Nino events have proven to be detrimental, with the 1982-83 and 1997-98 occurrences being the most intense of the twentieth century. During these instances, sea surface temperatures rose 9-18°C above normal.
The Madden-Julian Oscillation (MJO)
The MJO consists of two parts: an enhanced rainfall phase and a suppressed rainfall phase. Enhanced phase witnesses converging surface winds, resulting in increased rainfall due to upward moving air. On the other hand, during the suppressed phase, wind convergence appears at the top the atmosphere, causing air to sink, leading to lesser rainfall. This structure moves from the west to the east in the Tropics, creating variable weather patterns.
How ENSO Influences India’s Climate
The ENSO plays a significant role in dictating India’s climate, especially during monsoon season. El Nino brings below-average rainfall to India, leading to increased temperatures and worsening heat waves. Similarly, La Nina causes above-average rainfall, often resulting in flooding and landslides. Despite the damage, La Nina brings cooler temperatures, providing respite from heatwaves.
UPSC Civil Services Examination Questions Relating to ENSO
Previous years’ UPSC Civil Services Examination questions have addressed topics such as the Indian Ocean Dipole’s (IOD) influence on El Nino and unusual climate changes resulting from El Nino effects. Exam aspirants should thoroughly understand these concepts for better performance.
