Monsoon rainfall over India was higher during the mid-Pliocene period: Study

Mumbai: Monsoon rainfall over India was higher during the mid-Pliocene period — around three million years ago —  and a similar increase is expected in the future due to a warmer climate.

A study by the National Institute of Technology-Rourkela in the Sundergarh district of Odisha revealed several startling findings which were published in the prestigious International Journal of Climatology by the Royal Meteorological Society.

The Indian summer monsoon brings about 80 percent of India’s yearly rainfall and supports the livelihoods of hundreds of millions of people, especially those who depend on agriculture. 

Consistent monsoon rainfall is important for food production, water resources, and economic stability, not only in India but across South Asia.

As global temperatures increase because of climate change, the results of various studies conducted globally show a contradiction. While some studies suggest that rising temperatures may reduce rainfall, others conclude that monsoon rainfall could become stronger.

Given the monsoon’s strong impact on human livelihoods, it is important to understand how the Indian monsoon might respond.

To bridge this gap, Prof. Nagaraju Chilukoti, Assistant Professor, and Dr. Karishma Dahiya, Research Graduate, Department of Earth and Atmospheric Sciences, National Institute of Technology-Rourkela in collaboration with Prof. Raju Attada, Associate Professor, Department of Earth and Environmental Sciences, Indian Institute of Science Education and Research-Mohali, analysed how the monsoon behaved during warmer periods in Earth’s past to understand how it might behave in the future.

For this, the research team used climate models to compare two warm periods: the mid-Pliocene period and the projected future climate of the late 21st century (2071–2100) under a high-emissions scenario.

The mid-Pliocene period is a subdivision of the geologic time scale that spans approximately 3.3 to 3.0 million years ago. This period is frequently studied by scientists to better understand potential future climate change, as many aspects of Earth’s climate system during the Mid-Pliocene resemble conditions projected under ongoing global warming. 

Consequently, it serves as an important analog for assessing future climate responses, including temperature, sea level, and atmospheric circulation changes.

During the mid-Pliocene, global temperatures were about four degrees higher than pre-industrial levels. Climate projections today indicate that similar levels of warming could occur by the end of this century. Based on this, the researchers studied how the Indian Summer Monsoon responds when the planet becomes warmer.

The study shows that monsoon rainfall over India was higher during the mid-Pliocene, and a similar increase is expected in a warmer future climate.

However, the reasons behind the increase in rainfall are different in the two cases. In the mid-Pliocene, stronger winds and more active atmospheric circulation led to stronger monsoon rainfall. In the future scenario, the increase in rainfall is expected to happen because a warmer atmosphere can hold more moisture.

“The past is the key to the future and thus by examining the Mid-Pliocene warm climate, we gain crucial insights into how the Indian summer monsoon may respond to ongoing global warming. Our team observed that a warmer climate will likely increase the moisture in the atmosphere over the Indian Ocean and the Indian landmass, which could strengthen the movement of moisture toward India.

The team also noted that the peak monsoon rainfall month may shift from July to August. These findings are important for climate preparedness, agriculture, and water management in India and nearby regions,” said Prof Chilukoti.

According to him, a better understanding of rainfall patterns can help government officials and forecasting agencies improve early warning systems for floods and droughts. This can also help farmers in planning crop cycles and irrigation effectively if the timing and intensity of rainfall change.