El Niño and La Niña Explained: Causes, Effects, and Impacts

El Niño and La Niña—don’t they sound like scientific jargon or even the names of individuals who are related to the science field? 

However, these two terms are actually weather patterns that occur in the Pacific Ocean and can have significant impacts on global climate. 

Both of these patterns are different but ultimately are part of the larger climate phenomenon known as the El Niño-Southern Oscillation (ENSO). 

El Niño is characterised by warmer ocean temperatures while La Niña is characterised by cooler ocean temperatures. 

What is El Nino?

El Nino is a Spanish word that means "little boy" or "Christ Child." The phenomenon was named El Niño because South American fishermen first observed it in the early 17th century.

The name was inspired by the fact that the events, which were characterised by warm waters in the Pacific Ocean, were typically held in December.

El Niño refers to a large-scale climate interaction between the ocean and atmosphere. It is the periodic warming of sea surface temperatures in the central and eastern tropical Pacific Ocean, characterised by above-average temperatures, and typically occurs every 3 to 5 years, lasting about 9 to 12 months.

It is linked to high pressure in the western Pacific and negatively affects the Indian monsoon, impacting agriculture in India.

Effects:

• Weather Patterns: El Niño can lead to increased rainfall in the eastern Pacific (e.g., Peru and Ecuador) and drier conditions in regions like Australia and Southeast Asia, often resulting in droughts.
• Global Impact: It significantly disrupts normal weather patterns globally, influencing temperature, precipitation, and storm activity. For instance, it can cause wetter conditions in the southern United States while leading to droughts in parts of Africa.

What is La Nina?

La Niña, or 'small girl' in Spanish, is also known as El Viejo, or the 'cold event.' During this phenomenon, the water temperature in the Eastern Pacific becomes colder than usual.

This results in strong high pressure over the eastern equatorial Pacific and low pressure in the Western Pacific and parts of Asia.

La Niña leads to drought conditions in Peru and Ecuador, heavy flooding in Australia, higher temperatures in the Western Pacific and Indian Ocean, and improved monsoon rains in India. In fact, La Niña tends to be beneficial for India's monsoon season.

El Niño and La Niña events typically occur every 4 to 5 years, with El Niño being more common. Each event usually lasts between nine to twelve months.

Effects:

• Weather Patterns: La Niña typically brings about cooler ocean temperatures and can lead to increased rainfall in regions like Southeast Asia and Australia while causing drier conditions along the western coasts of South America.
• Global Impact: Similar to El Niño, La Niña influences global weather patterns, often resulting in opposite effects compared to El Niño. For example, it may lead to wetter conditions in the western Pacific and drier conditions in the eastern Pacific.

How do El Niño and La Niña Impact Weather Patterns in India?

El Niño refers to the periodic warming of sea surface temperatures in the central and eastern tropical Pacific Ocean. This phenomenon disrupts normal weather patterns across the globe.

Effects on India

• Reduced Rainfall: During El Niño years, India often experiences below-average rainfall, leading to drought conditions in many regions. The southwest monsoon, which is vital for Indian agriculture, tends to weaken significantly. 
• For instance, in 2023, the irregular monsoon rains caused widespread droughts affecting crops like rice and pulses.
• Higher Temperatures: El Niño is associated with warmer temperatures, which can exacerbate heat stress on crops and lead to lower agricultural yields.
• Impact on Agriculture: Key crops such as paddy, groundnuts, and sugarcane are particularly vulnerable during El Niño years. The lack of adequate rainfall can severely affect irrigation and crop production, potentially leading to increased food prices due to reduced supply.

Time Span

El Niño events typically occur every 3 to 7 years and usually last between 9 to 12 months. The effects are often felt most acutely during the monsoon season (June to September), when rainfall patterns are crucial for agriculture.

La Niña is characterised by cooler-than-normal sea surface temperatures in the central and eastern tropical Pacific Ocean. It is essentially the opposite of El Niño.

Effects on India

• Increased Rainfall: La Niña generally leads to above-average rainfall in many parts of India, particularly during the monsoon season. This can be beneficial for agriculture but may also result in excessive rainfall that causes flooding.
• Cooler Temperatures: The phenomenon is associated with cooler temperatures across northern India, which can lead to a more severe winter season. 
• For example, forecasts indicate that La Niña conditions could lead to a colder winter with extended monsoon effects into late September or October.
• Impact on Agriculture: While increased rainfall can enhance crop yields, it also poses risks such as flooding and waterlogging that can damage standing crops. Regions heavily dependent on timely harvests may face challenges if rainfall extends beyond optimal periods.

Time Span

La Niña events also occur every 3 to 7 years, with a typical duration of 9 months to 2 years. The onset usually happens between April and June, peaking between October and February, which aligns with the winter season in India.

Summary of Differences

El Niño and La Niña are two opposing phases of a significant climate pattern known as the El Niño-Southern Oscillation (ENSO). 

This phenomenon involves variations in ocean temperatures and atmospheric conditions in the tropical Pacific Ocean, which can have far-reaching effects on global weather patterns.

Source: Geology.com

Describing it simply, El Nino is when the ocean in the central and eastern Pacific Ocean gets warmer than usual. Whereas, La Niña is the opposite of El Niño. It happens when the ocean in the same area gets cooler than normal.

• El Niño = Warmer ocean water → More rain in some places, drought in others.
• La Niña = Cooler ocean water → Different weather effects, often opposite to El Niño.

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Conclusion

As of late 2024, the climate phenomenon El Niño that began in 2023 has officially ended. There is now a 57% probability that La Niña conditions will develop between October and December 2024. 

If established, this La Niña is expected to last until approximately January to March 2025. However, it is predicted to be a weak and short-lived event, contrasting with more intense episodes seen in previous years.

If La Niña does establish itself as anticipated, it will likely influence weather patterns into early 2025. The impacts of this event may include increased rainfall in certain regions while also bringing cooler temperatures, particularly affecting agricultural practices and weather patterns across various parts of the globe, including India.

Looking ahead, the next potential occurrence of El Niño or La Niña is uncertain but typically follows a cycle every 2 to 7 years. Given the current trends:

La Niña is expected to be present until early 2025.

The likelihood of transitioning back to El Niño conditions after that period remains low, particularly with models indicating a negligible chance of El Niño redeveloping during the same timeframe.

• 2024: Transitioning from El Niño to a potentially weak La Niña by late 2024.
• 2025: Expected continuation of La Niña effects into early months.
• Future occurrences: El Niño and La Niña events typically happen every few years, with the next significant event likely not occurring until after early 2025.

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