General Studies Paper -1
Context: The India Meteorological Department expects a La Niña to set in by late 2024 or early 2025, plus a milder winter due to this delay.
Emergence of La Nina
- Historically, the La Niña has usually formed during the monsoon or the pre-monsoon period, and it has formed only twice between October and December since 1950.
- Predicting La Nina: The oceanic Niño index (ONI) compares the three-month average sea surface temperatures in the East-Central Tropical Pacific with the 30-year average.
- When the difference between the two is 0.5º C or higher, it is an El Niño, and when it is –0.5º C or lower, it is a La Niña.
- Currently, it is around –0.3º C. To be classified as a full-fledged La Niña or El Niño, ONI values need to exceed the thresholds at least five times consecutively.
What is La Nina?
- It means Little Girl in Spanish. La Niña is also sometimes called El Viejo, anti-El Niño, or simply “a cold event.”
- The trade winds become stronger than usual, pushing more warmer waters towards the Indonesian coast, and making the eastern Pacific Ocean colder than normal.
- Impact on Weather Patterns:
- North America: La Niña is often associated with colder winters in the northern U.S. and Canada and warmer, drier conditions in the southern U.S. (such as in the southwestern states).
- South America: La Niña often causes droughts in countries like Peru and Ecuador while bringing more rain to Brazil.
- Asia and Oceania: La Niña tends to bring increased rainfall and a higher risk of flooding to countries like Indonesia, Australia, and parts of Southeast Asia.
Impact on India
- More rainfall in most regions, leading to a stronger monsoon.
- Increased risk of flooding and waterlogging in many parts of the country.
- Cooler temperatures during the post-monsoon and winter months.
- More cyclones in the Indian Ocean, increasing risks for coastal areas.
- Possible agricultural disruptions due to heavy rainfall, floods, and delayed harvesting.
Conclusion
- Climate change may increase the frequency and intensity of both La Niña and El Niño events, as rising sea and land temperatures disrupt the Pacific’s balance.
- Thus it would be a welcome development if a La Niña forms now or early next year and continues until the monsoon season. This would mean a less intense summer and more rains for India.