Why in the news?

The India Meteorological Department (IMD) has recently forecasted that La nina will affect the Indian monsoon in August and September.

What are El nino and La nina?

• El Nino and La Nina are climate phenomena resulting from ocean-atmosphere interactions in the central and eastern tropical Pacific Ocean, significantly influencing global weather patterns.
• El Nino (meaning “little boy” in Spanish) occurs when weak trade winds allow warm surface waters to accumulate near South America, reducing the usual upwelling of cold, nutrient-rich water. This leads to warmer-than-average sea surface temperatures.
• La Nina (meaning “little girl” in Spanish) involves strong trade winds pushing warm water towards Asia, increasing upwelling and resulting in cooler-than-average sea surface temperatures along South America.
• Together with a neutral phase, they form the El Nino-Southern Oscillation (ENSO) cycle.

How could the incoming La Nina impact global weather?

• Temperatures

• • • Global temperatures are likely to decrease compared to the recent record-breaking heat during the 2023-2024 El Nino event.
    • However, despite the cooling effect of La Nina, temperatures will still be higher than in previous decades due to the long-term warming trend from greenhouse gas emissions.

• Rainfall

• • • La Nina typically brings drier conditions to parts of Southeast Asia, Australia, and the southern United States.
    • Wetter than normal conditions are expected in parts of South America and eastern Africa.

• Tropical Storms

• • • La Nina is associated with increased tropical storm activity in the Atlantic Ocean and fewer storms in the Pacific.
    • The 2023 Atlantic hurricane season could see more intense storms due to La nina conditions.

• Economic Impacts

• • Droughts and floods linked to La nina can negatively impact agriculture, food security, and infrastructure in affected regions.
  • Fishing communities in the eastern Pacific may face reduced catches due to cooler ocean temperatures.

La nina’s impact on India

• Positive Impact on Monsoons

• • • La Nina generally leads to above-average monsoon rainfall in India. Since 1950, out of the 13 droughts India faced, only one was during a La nina year.
    • The extended La Nina event in 2022 led to a change in wind patterns, with winds blowing from north to south instead of the usual northwesterly direction.
    • This caused pollutants from agricultural burning in northern states to bypass Delhi and reach southern regions like Mumbai.

• Negative Impacts

• • La Nina can sometimes lead to heavy rains and floods in some parts of India, while the Western Ghats may receive average or below-average rainfall.
  • Winter rainfall is less than normal in north India, and snowfall over the Western Himalayas is also lower than usual during La Nina years.
  • Farmers may be at risk of losing their standing Kharif crops if heavy rains occur during this period.

Is climate change affecting EnSO?

• El Nino–Southern Oscillation (ENSO) is a global climate phenomenon that emerges from variations in winds and sea surface temperatures over the tropical Pacific Ocean.
  • Climate change is likely impacting the ENSO cycle, potentially altering the frequency and intensity of El Nino and La Nina events.
  • Studies suggest that global warming may change mean oceanic conditions in the Pacific, possibly leading to more frequent or intense El Nino events.
• The World Meteorological Organization (WMO) has indicated that climate change is expected to influence extreme weather events associated with EnSO, including more severe droughts, floods, and heatwaves.

 Way Forward:

• Develop more accurate climate models for better prediction of EnSO events and their impacts.
• Foster international collaboration to share data, resources, and strategies for managing EnSO-related challenges.

Mains PYQ:

Q Most of the unusual climatic happenings are explained as an outcome of the El-nino effect. Do you agree? (UPSC IAS/2014)

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