How India’s monsoon rain pattern has been changing amid climate change

How India’s monsoon rain pattern has been changing amid climate change

Context- The study titled ‘Decoding India’s Changing Monsoon Patterns: A Tehsil-level Assessment’ by Shravan Prabhu and Vishwas Chitale of the Council on Energy, Environment and Water (CEEW) analyzed high-resolution meteorological data from 1982 to 2022. The key findings are:

1. Rainfall during the southwest monsoon has increased in 55% of India’s 4,419 tehsils in the past 10 years.
2. 11% of tehsils have witnessed a decrease in rainfall.
3. Monsoon patterns in India have been fast-shifting and erratic in the past decade.
4. These changes have been mainly driven by the accelerating rate of climate change.

These findings highlight the significant impact of climate change on India’s monsoon patterns.

But first, a look at notable types of monsoon in India

India experiences two main types of monsoons:

1. Southwest Monsoon: Occurs from June to September. It begins in Kerala on the southwestern coast around June and spreads across the country. This monsoon is the primary weather system affecting India, providing relief from heat and contributing to the ecosystem and economy, particularly the cultivation of kharif crops.
2. Northeast Monsoon: Also known as the retreating monsoon, it occurs from October to December and impacts peninsular India. While not as intense as the southwest monsoon, it is vital for the growth of rabi crops.

THE FINDINGS

1. Rainfall increases in some of the traditionally drier regions and decreases in some of the high monsoon rainfall areas

The study observed the following changes in monsoon patterns:

• Traditionally drier areas such as Rajasthan, Gujarat, the Konkan region, central Maharashtra, and parts of Tamil Nadu have seen a significant increase in rainfall. These regions experienced a rise of more than 30% in the southwest monsoon rainfall in the past decade compared to the baseline of 1981–2011.
• Conversely, traditionally high monsoon rainfall areas like Assam and Meghalaya have seen a reduction in rainfall. Tehsils such as Pachim Nalbari Circle, Boitamari Circle, and Barnagar Circle of Assam received 30% less rainfall compared to the Long Period Average (LPA).

2. Regions with heightened rainfall experience more frequent heavy rainfall events

The study highlights the following trends in India’s monsoon patterns:

• Increased Rainfall: Southwest monsoon rainfall has increased in 55% of India’s tehsils. This increase is primarily due to short-duration, heavy rainfall, which often leads to flash floods.
• Frequency of Heavy Rainfall: Nearly 64% of tehsils have seen an increase in the frequency of heavy rainfall days by 1-15 days per year over the last decade.
• Rainfall Extremes: While the study does not show significant trends in the intensity of wet rainfall extremes, the proportion of total seasonal rainfall attributed to these extremes is increasing during the southwest monsoon.
• Impact on Flash Floods: The changing distribution of rainfall within a season could be one of the reasons behind the recent occurrences of flash floods in places like Delhi, Uttarakhand, Himachal Pradesh (in 2023), and Bangalore (in 2022).

3. Changes in monsoon patterns can affect agriculture output and ecosystems

The study found that:

• Southwest monsoon rainfall has decreased in 11% of tehsils over the past decade.
• A significant number of these tehsils are in the Indo-Gangetic plain, northeast India, and the upper Himalayan region, which are crucial for India’s agricultural output.
• These regions rely heavily on the southwest monsoon for kharif season agricultural activities. A decrease in rainfall can severely affect the output.
• These regions have fragile ecosystems that are particularly vulnerable to extreme climate events like floods and droughts. This makes the decrease in rainfall a cause for concern.

4. Rainfall is not distributed evenly throughout the seasons and months

The study found:

• Most tehsils with decreased southwest monsoon rainfall saw a decline during the initial monsoon months of June and July, which are crucial for sowing kharif crops.
• Conversely, 48% of tehsils in India experienced an increase in October rainfall by more than 10%, possibly due to the delayed withdrawal of the southwest monsoon. This could impact the sowing of rabi crops.

5. Northeast monsoon rainfall also increased in some regions

• Over the last decade, about 80% of tehsils in Tamil Nadu, 44% in Telangana, and 39% in Andhra Pradesh have seen an increase of more than 10% in rainfall during the retreating monsoon.
• Additionally, states like Odisha, West Bengal, Maharashtra, and Goa have also experienced an uptick in rainfall during this period.

Conclusion- The study reveals significant shifts in India’s monsoon patterns over the past decade. While some regions have seen an increase in rainfall, others have experienced a decrease. These changes, driven by climate change, have significant implications for India’s agriculture and ecosystems.

The increase in heavy, short-duration rainfall could lead to more flash floods, while decreased rainfall in key agricultural regions could impact crop yields. The findings underscore the urgent need for adaptive and resilient strategies to mitigate the impacts of climate change on India’s monsoon patterns.