Overview
A joint research paper by IMD and the IITM shows that rising temperatures and falling rainfall are reshaping India’s climate zones. The study attributes the changes to the Victoria Mode (VM), a lesser‑known Pacific Ocean phenomenon.
Key Developments
- In north‑west India, the semi‑arid steppe zone expanded from 25.7% (1951‑80) to 33.1% (1991‑2020); the milder temperate zone fell from 25.8% to 18.7%.
- In the north‑east, the tropical savannah area dropped from 18.4% to 11.8%, while the temperate zone rose to 82.5%.
- Peninsular India saw the steppe zone shrink from 30.3% to 16.4%, while the savannah grew to 75.7%.
- The study links the negative phase of VM to reduced moisture transport over western and eastern Uttar Pradesh, Bihar, and Gangetic West Bengal, causing drying in these fertile plains.
Important Facts
The researchers used IMD’s gridded data (0.25° ≈ 25 km) for five consecutive 30‑year windows, starting each decade after the previous one. They compared North Pacific sea‑surface temperatures with rainfall over the northern plains (1981‑2020) to isolate the VM signal.
While the PDO and the ENSO are known to affect the Indian monsoon, the paper notes that most VM events have been followed by El Niño episodes, though a direct causal link is not established.
Exam Relevance
Understanding VM adds depth to the GS3 syllabus on climate variability and its impact on agriculture, water security, and migration. The shift from savannah to temperate zones in the Gangetic belt raises concerns about food‑grain production, a key topic for questions on food security and rural livelihoods. The study also illustrates the use of high‑resolution gridded datasets, relevant for questions on climate monitoring and data‑driven policy making.
Way Forward
- Integrate VM monitoring into the existing monsoon forecasting framework to improve seasonal outlooks.
- Strengthen water‑conservation and drought‑mitigation programmes in the newly expanded steppe zones of north‑west India.
- Promote climate‑resilient cropping patterns in regions transitioning from tropical savannah to temperate conditions.
- Encourage interdisciplinary research linking Pacific Ocean dynamics (VM, PDO, ENSO) with Indian monsoon behaviour.
Timely policy action based on these scientific insights can mitigate food‑security risks and reduce displacement of vulnerable populations.