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Ancient Pollen Evidence from Chhattisgarh Suggests Stronger Medieval Monsoon in India

ANALYSIS

Scientists from the Birbal Sahni Institute of Palaeosciences (BSIP), Lucknow, have discovered evidence indicating that the Indian Summer Monsoon (ISM) during the medieval period was significantly stronger than previously estimated. The findings emerged from the study of ancient pollen grains preserved in the sediments of Raja Rani Lake located in Korba district of Chhattisgarh.The research assumes importance because the study area lies within India’s Core Monsoon Zone (CMZ), a region that receives nearly 89–90% of India’s annual rainfall under the influence of the ISM. Understanding past monsoon behaviour in this zone is critical for reconstructing long-term climatic variability and improving future climate projections.

Study of Ancient Pollen and Lake Sediments

Researchers extracted a 40-centimetre sediment core from Raja Rani Lake. The sediment layers preserved environmental records spanning nearly 2,500 years.Using palynology — the scientific study of pollen grains and spores — scientists reconstructed past vegetation and climatic conditions.The analysis revealed:

• Dominance of moist and dry tropical deciduous forests during the medieval period.
• Presence of forest-associated pollen indicating warm and humid climatic conditions.
• Absence of evidence suggesting major dry phases within the CMZ during that period.

The findings indicate that central India experienced a strong and sustained monsoon regime during the Medieval Climate Anomaly (MCA).

Medieval Climate Anomaly and Monsoon Intensification

The study identified the period roughly between 1060 CE and 1725 CE as a phase of intensified monsoon activity linked to the Medieval Climate Anomaly (MCA).Scientists attributed the stronger monsoon to several interconnected global and regional climatic drivers:

• La Niña-like conditions, generally associated with stronger Indian monsoons.
• Northward movement of the Inter Tropical Convergence Zone (ITCZ).
• Positive temperature anomalies.
• Increased sunspot activity and higher solar radiation.

The combined effect of these factors likely strengthened atmospheric circulation and enhanced rainfall over the Indian subcontinent.

Importance for Climate Science and Policy

The study has major implications for understanding long-term climate variability in South Asia.The reconstructed palaeoclimatic records may help in:

• Improving monsoon prediction models.
• Developing advanced paleoclimate simulations.
• Understanding future rainfall variability under climate change scenarios.
• Supporting evidence-based climate policy planning.

The research also contributes to better understanding of the Holocene climatic evolution, particularly during the Meghalayan Age, which represents the current geological age.

STATIC PART

Birbal Sahni Institute of Palaeosciences (BSIP)

Core Monsoon Zone (CMZ)

Key Scientific Terms

Updated – 12 January 2026 ; 06:47 PM | PIB |PIB News Source