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

El Niño and La Niña – don’t sound like scientific terms, or even the names of individuals associated with the scientific field?

However, both terms are actually weather patterns that occur in the Pacific Ocean and can have a significant impact on global climate.

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

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

What is El Niño?

El Niño is a Spanish word meaning “little boy” or “holy child.” This phenomenon was named El Niño because it was first observed by South American fishermen in the early 17th century.

The name is inspired by the warm waters of the Pacific Ocean that characterize this event, which usually takes place in December.

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

It is associated with high pressure in the western Pacific and has a negative impact on the Indian monsoon, affecting Indian agriculture.

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Effect:

• Weather patterns: El Niño can lead to increased rainfall in the eastern Pacific, such as Peru and Ecuador, and dry conditions in areas such as Australia and Southeast Asia, often resulting in droughts.
• Global impacts: It severely disrupts normal weather patterns around the world, affecting temperatures, precipitation and storm activity. For example, it could lead to wetter weather in the southern United States and drought in parts of Africa.

What is La Niña?

La Niña, which means “the little girl” in Spanish, is also known as “El Viejo” or “the cold event.” During this phenomenon, water temperatures in the eastern Pacific Ocean become colder than normal.

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

La Niña has led to droughts in Peru and Ecuador, severe flooding in Australia, rising temperatures in the western Pacific and Indian Ocean, and increased monsoon rainfall in India. In fact, La Niña tends to be good for India’s monsoon season.

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

Effect:

• Weather patterns: La Niña typically causes ocean temperatures to drop and can lead to increased rainfall in areas such as Southeast Asia and Australia, while drying out areas along the west coast of South America.
• Global Impact: Similar to El Niño, La Niña affects global weather patterns, often having the opposite impact of El Niño. For example, it could cause the climate in the western Pacific to become wetter and the climate in the eastern Pacific to become drier.

How do El Niño and La Niña affect weather patterns in India?

El Niño is a periodic increase in sea surface temperatures in the central and eastern tropical Pacific. This phenomenon disrupts normal weather patterns around the world.

Impact on India

• Reduced rainfall: During El Niño, India often experiences below-average rainfall, leading to drought in many areas. The southwest monsoon, vital to Indian agriculture, tends to weaken significantly.
• For example, in 2023, irregular monsoon rains caused widespread drought, affecting crops such as rice and beans.
• Rising temperatures: El Niño is associated with rising temperatures, which can exacerbate heat stress in crops and lead to reduced agricultural yields.
• Impact on agriculture: During El Niño, major crops such as rice, peanuts and sugarcane are particularly vulnerable. Insufficient rainfall can severely impact irrigation and crop production and could lead to higher food prices due to reduced supplies.

time span

El Niño events typically occur every 3 to 7 years and usually last 9 to 12 months. The impact is usually most pronounced during the monsoon season (June to September), when rainfall patterns are critical for agriculture.

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

Impact on India

• Increased rainfall: La Niña typically results in above-average rainfall in many parts of India, especially during the monsoon season. This is good for agriculture, but can also lead to excessive rainfall, which can lead to flooding.
• Falling temperatures: This phenomenon is associated with falling temperatures in northern India, which may lead to harsher winters.
• For example, forecasts indicate that La Niña conditions could lead to a cold winter with monsoon effects lasting until late September or October.
• Impact on agriculture: While increased rainfall can increase crop yields, it also poses risks such as flooding and waterlogging, which can damage standing crops. Regions that rely heavily on timely harvests could face challenges if rainfall extends beyond optimal times.

time span

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La Niña events also occur every 3 to 7 years and usually last from 9 months to 2 years. Onset usually occurs between April and June, peaking from October to February, coinciding with the Indian winter.

Difference summary

aspect	El Niño	La Niña
temperature	rising ocean temperatures	Ocean temperatures cool
rainfall impact	Reduced rainfall, leading to drought	Increased rainfall, possible flooding
Temperature effect	higher temperature	lower temperature
agricultural impact	Drought negatively affects crops	Positive impact but potential flood risk
time span	Every 3-7 years; lasts 9-12 months	Every 3-7 years; lasts 9 months to 2 years

El Niño and La Niña are two opposite phases of the important climate pattern El Niño Southern Oscillation (ENSO).

This phenomenon involves changes in ocean temperatures and atmospheric conditions in the tropical Pacific, which can have profound effects on global weather patterns.

Source: Geological Network

Simply put, El Niño is when the ocean in the central and eastern Pacific becomes warmer than usual. However, La Niña is the opposite of El Niño. This occurs when ocean temperatures in the same area are cooler than normal.

• El Niño = Warming waters → more rainfall in some places and drought in others.
• La Niña = cooler water → different weather effects, usually the opposite of El Niño.

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in conclusion

By the end of 2024, the El Niño climate phenomenon that started in 2023 will officially end. Currently, the probability of La Niña conditions between October and December 2024 is 57%.

If La Niña holds true, it is expected to last until around January to March 2025. However, this is expected to be a weak and short-lived event compared to more intense events seen in previous years.

If La Niña does occur as expected, it could affect weather patterns into early 2025. Impacts of the event could include increased rainfall in some areas, along with lower temperatures, particularly affecting agricultural practices and weather patterns around the world, including in India.

Looking ahead, the next potential El Niño or La Niña event is uncertain, but it typically occurs in cycles every 2 to 7 years. Given current trends:

La Niña conditions are expected to last until early 2025.

The likelihood of a transition back to El Niño after this period remains low, especially as models indicate a negligible likelihood of El Niño developing again within the same time frame.

• 2024: By the end of 2024, El Niño will transition into a potentially weaker La Niña.
• 2025: La Niña effects are expected to continue into the first few months.
• What’s next: El Niño and La Niña events typically occur every few years, and the next major event may not occur until after early 2025.

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Source: https://dinhtienhoang.edu.vn
Category: Optical Illusion