A new study published in the journal Science Advances has established that large volcanic eruptions have been a primary driver of variations in Asian summer monsoon rainfall over the past 500 years. By analyzing tree-ring records and climate model simulations, researchers found that these eruptions consistently pushed the monsoon system into a distinct three-part pattern: drying in central Asia, wetting in northern Asia and the South China Sea, and drying again in southern Asia.
This pattern mirrors the natural, long-term climate oscillation known as the Pacific Decadal Oscillation (PDO) but is triggered abruptly by volcanic events. The study links this forced pattern to major historical climate events, including the late-18th century droughts in India and the failure of the Nile River floods in 1791–1792, which followed the 1783 Laki eruption in Iceland.
The research, led by scientists from the University of Cambridge and other institutions, used data from over 300 tree-ring chronologies across Asia. It demonstrates that volcanic aerosols injected into the stratosphere cool the Earth's surface, particularly over the Asian continent, which weakens the monsoon circulation and reorganizes atmospheric patterns in this predictable way.
This finding recasts the understanding of centuries of flooding and drought across the continent, showing they were not random but part of a coherent, volcanically forced climate response. The authors note that understanding this mechanism is crucial for improving climate models and preparing for future volcanic impacts on water resources and agriculture in monsoon-dependent regions.
