The Hindu: Published on 28 May 2025:
Why in News:
The India Meteorological Department (IMD) announced that the southwest monsoon set in over Kerala on May 24, a week earlier than its usual date of June 1.
This is the earliest onset in 16 years, since May 23, 2009.
Background
The southwest monsoon is India’s most important weather event, crucial for agriculture, water security, and economic stability.
Since 1975, the monsoon’s earliest onset was on May 19, 1990.
The onset prediction has always been a complex task due to multiple influencing factors like sea temperatures, wind patterns, and global climate anomalies.
Key Issues
Lack of Predictability: Despite technological advances, accurately forecasting the exact onset of monsoon remains a scientific challenge.
No Direct Link to Rainfall Abundance: An early onset does not guarantee a bountiful monsoon; in fact, 2009 also had an early onset but ended with a severe drought.
Complex Drivers: Factors like El Niño, La Niña, cyclones, wind anomalies, and Arctic warming interact in non-linear and unpredictable ways.
Scientific Dimensions
Onset Mechanics: The monsoon progresses from the northwest Pacific to Andaman Sea, then to the Bay of Bengal, finally reaching Kerala.
Role of Cyclones: Cyclones near the west coast or Bay of Bengal can pull the monsoon trough northward, triggering early arrival.
El Niño/La Niña Role:
El Niño tends to weaken monsoons, while La Niña may strengthen them.
However, these correlations don’t consistently predict onset dates.
Unusual SSTs: 2024 had strange sea surface temperature (SST) patterns, with warm anomalies in the east and west Pacific and cool center, challenging the conventional definitions of La Niña.
Long-Term Trends
Systematic Delay Since 1970s: Studies suggest a regime shift in the climate system may have led to a gradual delay in monsoon onset, though causes remain unclear.
Impact of Global Warming:
Decadal variability and rising temperatures have introduced new layers of complexity.
2023-24 experienced record warmth, likely influencing the current monsoon behaviour.
Arctic warming and changing cyclone patterns may also be altering monsoon dynamics.
Comparison with 2009
Both 2009 and 2025 had early monsoon onsets.
2009 was a mild El Niño year and ended in a monsoon drought.
However, 2025 is currently predicted to be a neutral ENSO (El Niño-Southern Oscillation) year, although some models hint at a possible El Niño formation.
Caution is advised in drawing parallels due to differences in oceanic and atmospheric conditions.
Impact on Seasonal Rainfall
Erratic Rainfall Patterns: Early onset doesn’t ensure uniform rainfall; some regions face floods, others face droughts.
Delayed Withdrawal: Some parts of India are witnessing a merging of southwest and northeast monsoon phases.
Changing Distribution: Uneven rain distribution is becoming the new normal, raising concerns for agriculture and water management.
Insights & Way Forward
Monsoon prediction needs to go beyond onset dates to include intra-seasonal variation, distribution, and withdrawal.
More comprehensive models that integrate climate variability, global warming trends, and regional atmospheric changes are needed.
Policy relevance: Agriculture planning, irrigation management, and disaster preparedness depend on improved forecasts.
Conclusion
2025’s early monsoon onset is a curious climatic event, not yet fully understood.
It underscores the increasing unpredictability of weather systems in a warming world.
Instead of celebratory optimism, it calls for cautious preparedness, scientific rigor, and investment in climate research.
