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Climate Change: The culprit behind India's erratic rainfall

By Bibek Bhattacharya,

Monsoon rainfall will get 5% stronger with every 1 degree Celsius rise in global temperatures.

Global warming is increasing the likelihood of violent monsoon rain and flooding. (Getty Images)

The effect of climate change on India won’t just be played out in the form of dramatic, extreme events like super cyclones. It will play out by slowly but surely changing the nature of the major weather systems that the country depends on, like the monsoon. A new study shows the way that increasing global warming is going to turn the monsoon into an erratic, destructive force.

The study, Robust Increase Of Indian Monsoon Rainfall And Its Variability Under Future Warming In CMIP6 Models, was published on 14 April in the Earth System Dynamics journal. Researchers from Germany and US studied 31 different climate models to understand how the Indian monsoon would change according to different global heating scenarios. In the best case scenario where climate action ensures that the below 2 degrees Celsius warming goal of the Paris Agreement is met, the monsoon will increase by almost 10% from the baseline of 1985-2015. However, if global warming isn’t tackled effectively, mean seasonal rainfall might increase by as much as 24% by 2100.

The researchers also found that monsoon rains would likely increase by 5% for every 1 degree Celsius of warming. Among other outcomes, any erratic changes in the monsoon are likely to affect food security. “Crops need water especially in the initial growing period, but too much rainfall during other growing states can harm plants—including rice on which the majority of India's population is depending for sustenance. This makes the Indian economy and food system highly sensitive to volatile monsoon patterns,” said study co-author Julia Pongratz from Ludwig-Maximilian University (LMU) in Germany.

This study is the latest in a line of new research over the past three years that have reached similar conclusions about the future of Indian monsoon. The 2018 Special Report On The Ocean And Cryosphere In A Changing Climate (SROCC) from the Intergovernmental Panel on Climate Change (IPCC) stated that the monsoon is going to be more erratic through the 21st century. The Indian government’s Assessment Of Climate Change Over The Indian Region, published last year, stated that the monsoon is expected to become more extreme in the coming decades. The report predicts that there will be longer dry spells, which would alternate with heavy rains.

A study in January this year showed how a band of tropical heavy rainfall is moving steadily north from near the equator as the world heats up. The research concluded that as the northern hemisphere continues to heat up and lose Arctic sea ice and Himalayan glaciers, this band will gravitate towards the hotter zone. In turn, this will lead to an increase in Indian monsoon rainfall, as well as an increase in extreme weather events.

The India Meteorological Department (IMD), has forecast a normal to above normal monsoon for 2021. This means that the rainfall between June-September will be 98% of the Long Period Average (LPA). However, in recent years, while the monsoon has remained close to the LPA, the nature of the rainfall over the monsoon months has also been erratic. For example, in 2020, Delhi experienced excess rains in July, followed by 72% less than average rainfall in the first half of August. In that same time, there were instances of cloudbursts in several parts of the country, including 820mm of rain over 24 hours in the Nilgiris in Tamil Nadu, triggering massive landslides and flooding. Kerala, Bihar, Assam and some other states have seen massive annual monsoon floods for the past three years.

Perhaps keeping this in mind, the IMD announced on 16 April that it will also begin making monthly probabilistic forecasts for each of the four monsoon months. It will also issue a special forecast for the ‘Monsoon Core Zone’, spanning Madhya Pradesh, Maharashtra, Chhattisgarh, Jharkhand, Bihar, Karnataka, Odisha, Rajasthan and Gujarat, states that show rainfall variability.

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