Multidecadal Variability in Monsoonal Climate Systems

Monsoonal regimes exhibit pronounced fluctuations not only from year to year but also on multidecadal timescales, reflecting the interplay of internal ocean–atmosphere dynamics and external forcing. These low-frequency variations arise from coherent oscillations in sea surface temperature patterns across major ocean basins, notably the Atlantic and Pacific, and are expressed in shifts of monsoon intensity, onset timing and spatial distribution of rainfall. Such variability can amplify or dampen the impact of anthropogenic warming, thereby influencing water resources, agriculture and extreme events across densely populated regions of South Asia, West Africa and East Asia. Improved understanding of these slow modes of variability is critical for decadal prediction, risk assessment and adaptation planning, since they underlie prolonged wet or dry epochs that affect ecosystem resilience, food security and infrastructure stability.

Research from Nature Portfolio

New palaeoclimate reconstructions from the Bay of Bengal have revealed a tight correspondence between Indian Summer Monsoon rainfall and Atlantic multidecadal oscillations over the last two millennia. Variations in sea surface salinity and temperature proxies indicate that wetter and drier monsoon phases align with warm and cold phases of the Atlantic regime, respectively. These findings mirror observed twentieth-century relationships and point to a persistent inter-hemispheric thermal contrast mechanism that modulates large-scale circulation. By extending the record beyond the instrumental era, this work confirms that Atlantic forcing has been a long-term driver of monsoon swings and underlines the importance of extra-tropical teleconnections in shaping future trends under global warming.

Multidecadal Variability in Monsoonal Climate Systems publication trend

The graph below shows the total number of articles in multidecadal variability in monsoonal climate systems across all publications each year (not limited to Nature Index journals).

Technical terms

Multidecadal Variability: Natural climate fluctuations occurring on timescales of roughly 20 to 70 years, driven by internal oceanic and atmospheric dynamics.

Atlantic Multidecadal Oscillation (AMO): A long-period oscillation in North Atlantic sea surface temperatures that modulates regional climate patterns.

Pacific Decadal Oscillation (PDO): A Pacific-wide pattern of sea surface temperature anomalies with phases lasting multiple decades, influencing monsoon strength.

Teleconnection: A climate linkage whereby anomalies in one region affect weather and circulation patterns in distant regions through atmospheric or oceanic pathways.

References

1. Global-scale interdecadal variability a skillful predictor at decadal-to-multidecadal timescales for Sahelian and Indian Monsoon Rainfall. npj Climate and Atmospheric Science (2022).
2. The connection between the Atlantic Multidecadal Oscillation and the Indian Summer Monsoon since the Industrial Revolution is intrinsic to the climate system. Environmental Research Letters (2018).
3. Decadal to multi-decadal scale variability of Indian summer monsoon rainfall in the coupled ocean-atmosphere-chemistry climate model SOCOL-MPIOM. Climate Dynamics (2017).
4. Coherent response of the Indian Monsoon Rainfall to Atlantic Multi-decadal Variability over the last 2000 years. Scientific Reports (2020).