Volcanic eruptions can help predict Indian monsoon, says study

Large volcanic eruptions can help forecast the monsoon over India according to a new study led by an Indian-German research team.

“What seems to be a paradox is in fact due to a stronger coupling between the monsoon over large parts of South and South-East Asia and the El Niño phenomenon after an eruption,” the study said.

Researchers combined data from meteorological observations, climate records, computer model simulations, and geological archives such as tree-rings, corals and ice-cores from past millennia of Earth history to study the correlation between volcanic eruptions and Indian monsoon.

Study findings

They found that the monsoon synchronized with El Niño, making it easier to anticipate the strength of seasonal rainfall in the Indian subcontinent.

"The tiny particles and gases that a large volcano blasts into the air enter into the stratosphere and remain there for a few years. While the volcanic matter in the stratosphere to some extent blocks sunshine from reaching the Earth's surface, the reduced solar forcing increases the probability of an El Niño event in the next year," said R. Krishnan from the Indian Institute of Tropical Meteorology in Pune.

"This is because less sunshine means less warmth and hence a change of temperature differences between the Northern and Southern hemisphere, which in turn affects the atmospheric large-scale circulation and precipitation dynamics. Advanced data analysis now reveals that large volcanic eruptions are more likely to promote the coincidence of warm El Niño events over the Pacific and Indian monsoon droughts - or, in contrast, cool La Niña events over the Pacific and Indian monsoon excess,” he further explained.

Observations

The study suggests that the monsoon over Indian “strongly depends on the El Niño / Southern Oscillation - a climatic phenomenon in the tropical Pacific Ocean.” The phenomenon is called 'the boy' in Spanish.

"The synchronization between tropical Pacific Ocean and Indian monsoon is changing over time, with human-made global warming being one of the factors, worsening the accurate prediction of the monsoon," said Norbert Marwan from the Potsdam Institute for Climate Impact Research (PIK).

"This in fact confirms a hypothesis that our colleagues Maraun and Kurths launched 15 years ago. The new findings now suggest a novel, additional path for monsoon predictions that are crucial for agricultural planning in India,” he added.

The findings can help further develop climate models and assess the regional impact of geoengineering experiments.

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