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Impact of Human Activities on El Nino and La Nina Events


A recent study highlights concerns regarding the influence of human activities on El Nino and La Nina events. It suggests that the Walker Circulation has shifted since the industrial era, potentially leading to an increased occurrence of multi-year El Nino and La Nina events.


GS I: Geography

Dimensions of the Article:

  1. Walker Circulation
  2. Key Details from the recent study
  3. El Nino
  4. La Nina
  5. El Nino-Southern Oscillation (ENSO)

Walker Circulation:

The Walker Circulation is a significant atmospheric circulation pattern located in the tropical Pacific region of the Earth. It exerts a substantial influence on climate and weather patterns both within the tropics and on a global scale. Here are some key characteristics of the Walker Circulation:

  • Tropical Pacific Region: The Walker Circulation is primarily centered in the tropical Pacific Ocean but extends its effects to regions far beyond this area.
  • Climate and Weather Impact: This atmospheric system of winds plays a crucial role in shaping climate and weather patterns in tropical regions and can have cascading effects on weather systems worldwide.
  • El Nino and La Nina: The strength of the Walker Circulation is closely tied to phenomena known as El Nino and La Nina. A weaker Walker Circulation is associated with El Nino events, which can bring about irregular and extreme weather conditions in various parts of the world. In contrast, a stronger Walker Circulation typically signals La Nina, which can lead to its own set of climate anomalies.

Key Details from the recent study

Recent studies on the Walker Circulation and its relationship to climate change and volcanic eruptions have provided several important insights:

  • Slowing Transition from El Nino to La Nina: The transition from El Nino to La Nina has shown a slight slowing over time. This suggests that multi-year climate patterns may become more frequent in the future, leading to increased risks of droughts, fires, heavy rainfall, and floods.
  • Potential Influence of Greenhouse Gas Emissions: While the overall strength of the Walker Circulation has not yet decreased, researchers speculate that elevated carbon dioxide levels resulting from greenhouse gas emissions could weaken it over time.
  • Climate Models Predictions: Many climate models predict a decline in the Walker Circulation by the end of the century, indicating potential future changes in global weather patterns.
  • Link Between Volcanic Eruptions and Walker Circulation: The study identified a connection between volcanic eruptions and the weakening of the Walker Circulation. Volcanic eruptions have led to El Nino-like conditions in the past.
  • Significant El Nino Events Following Volcanic Eruptions: Researchers noted three significant El Nino events in the twentieth century that followed volcanic eruptions, including Mount Agung in 1963, El Chichón in 1982, and Mount Pinatubo in 1991. These events highlight the complex interactions between volcanic activity and climate systems.

El Nino:

El Nino is a climate pattern characterized by the unusual warming of surface waters in the Tropical Pacific Ocean. Here are some key points about El Nino:

  • Spanish Name: “El Nino” means “Little Boy” in Spanish, and it is named so because it often peaks around Christmas, which is traditionally associated with the birth of the Christ child.
  • Frequency: El Nino events occur more frequently than their counterpart, La Nina.
  • Effect on Indian Monsoon: El Nino is known to have a suppressing effect on monsoon rainfall in India. It can lead to drier-than-usual conditions and droughts in certain regions.
  • Cause: El Nino is caused by the weakening or reversal of trade winds in the tropical Pacific Ocean. Typically, trade winds blow from east to west, pushing warm surface waters towards the western Pacific.

La Nina:

La Nina, often referred to as “Little Girl” in Spanish, is a climate pattern characterized by the unusual cooling of the Tropical Pacific Ocean. Here are some key points about La Nina:

  • Spanish Name: “La Nina” translates to “Little Girl” in Spanish. It is sometimes referred to as “El Viejo” (The Old Man), anti-El Nino, or simply “a cold event.”
  • Effect on Indian Monsoon: Unlike El Nino, La Nina tends to promote rainfall over India. It can lead to wetter-than-usual conditions.
  • Cause: La Nina occurs as a result of the strengthening of the trade winds in the tropical Pacific Ocean. During La Nina events, these trade winds become even stronger, intensifying the east-to-west flow of warm surface waters across the equatorial Pacific.
  • Sea Surface Temperatures: The strengthening of the trade winds during La Nina leads to cooler-than-average sea surface temperatures in the central and eastern equatorial Pacific.

El Nino-Southern Oscillation (ENSO):

ENSO is a complex climate phenomenon that results from the interaction between ocean and atmospheric conditions in the equatorial Pacific region. Here are some key points about ENSO:

  • Southern Oscillation: The term “southern oscillation” in ENSO refers to differences in sea-level air pressure between the western and eastern Pacific Oceans. These pressure differences play a crucial role in the development of ENSO events.
  • El Nino and La Nina: ENSO is characterized by two primary phases—El Nino and La Nina. These represent the warm and cool phases of the ENSO cycle, respectively.
  • Frequency: El Nino and La Nina events typically occur every 2 to 7 years. La Nina events can last between one and three years, while El Nino events are less likely to persist for more than a year.
  • Multi-year Events: Multi-year El Nino and La Nina events are those that continue for more than one year without returning to normal conditions in between. These extended phases are relatively unusual.
  • Recent Events: In 2023, La Nina concluded a three-year period, and El Nino made its presence felt. Such long-lasting ENSO phases are not common and can have significant impacts on global weather patterns.

-Source: Down To Earth

March 2024