When monsoon plays truant!

A recent study by the Council on Energy, Environment and Water (CEEW) found that very few (less than 4 percent) of Indian farmers have adopted sustainable agricultural practices and systems. Scaling up sustainable agriculture is critical to improve farm incomes and bolster India's nutrition security in a climate-constrained future.

What could happen when monsoon too plays truant in these circumstances?

The monsoon, a unique phenomenon.

The monsoon arrives in India following the unfurling of a series of unique events. The movement of the sun to the north during summer heats up the Indian landmass to create an area of low pressure that attracts moisture-laden winds from the cooler ocean to form the monsoons. Low pressure near the equator also pulls together moist winds to form a cloud belt around the earth.

Heat pushes this cloud belt forward as it merges with the monsoon winds to form a trough. The advancing monsoon is helped by jet streams blowing from the west to east. Western Ghats, the Eastern Ghats and the Himalayas offer enough highlands to make the moist winds yield rains while the Himalayas confine the monsoons within the Indian subcontinent.

Watch this video to know more on how the monsoon clouds form over India

The summer monsoon, India’s lifeline!

And the summer/south west monsoon rainfall is crucial for food security in India! Food production has been rising India since the mid-20th century due to technological advances and increased inputs during the Green Revolution. For example, total food production of staple crops has tripled over 1951–2016 with  yields of food grain (cereals and pulses), rice, wheat, and cereals (Rice, Jowar, Bajra, Maize, Wheat, and Barley) having increased at a rate of 25, 27, 43, and 15.5 kg/ha, respectively, over this period.

While changes in agricultural management practices such as expansion of irrigation facilities and the use of fertilisers and improved seeds after the green revolution have aided this progress, these agricultural practices continue to be unsustainable and rainfall is crucial for agriculture in India. However, rainfall patterns too are changing rapidly with climate change in the country.

Monsoon predicted to become become erratic with global warming

The study titled 'Robust increase of Indian monsoon rainfall and its variability under future warming in CMIP6 models' in the journal Earth System Dynamics by Anja Katzenberger, Jacob Schewe, Julia Pongratz, Anders Levermann predicts that global warming will lead to erratic and wetter monsoons in the years to come in India. The changes will affect rainfall mainly in the Himalayan region and to the northeast of the Bay of Bengal, as well as the west coast of India.

The monsoon rainfall will increase by five percent for every degree celsius of warming, informs the author of the study.

Another study titled ''Remote and local drivers of Pleistocene South Asian summer monsoon precipitation: A test for future predictions' published in the journal Science Advances by Steven C. Clemens et al that analysed data from the past million years also predicts that amount and extreme variability of rainfall over South Asia is predicted to increase due to increased 21st-century greenhouse gases accompanied by an increased supply of moisture from the southern hemisphere Indian Ocean.

Increase in production shows only one side of the story

In their study, 'Future exacerbation of hot and dry summer monsoon extremes in India' published in the journal Climate and Atmospheric Science,  Vimal Mishra, Kaustubh Thirumalai, Deepti Singh and Saran Aadhar inform that despite projections of summer monsoon intensification in India, the rise in surface air temperatures and monsoon variability will lead to more severe hot and dry monsoon extremes over India, thus having a negative impact on the yields of many staple crops in the country.

This connection between climate change and agricultural production in the context of increasing population and nutritional demands calls for the need to have a better understanding of monsoon variability in the context of greenhouse warming.

There continues to be lack of information on the combined impact of rainfall and air temperature extremes on crop production during the summer monsoon season over India. Studies in other parts of the world show that  concurrent hot and dry extremes can have a negative impact on food production, water availability, and human health.

This  study explores the impact of seasonal hot and dry extremes on staple crop yields in India during the monsoon season and the factors responsible for these extreme fluctuations by looking at simulations for the historic (1971–2000) and future
(2006–2100) data on temperature and rainfall.

The study finds that:

Fluctuations in monsoon rainfall are found to greatly affect total food grain and rice yields in India, with decreased rainfall associated with reduced production. Decreased rainfall can also affect winter crops as normally the effect of monsoon rainfall remains after the end of monsoons and helps the soil to retain moisture that helps crop growth outside the monsoon.

Temperature irregularities during the monsoon season are associated with changes in crop yields with warmer temperatures linked to reduced crop production. While monsoon season rainfall causes more than 50 percent of variation in food grain and rice production, monsoon temperature causes about 22 percent of variation in food grain yields. Thus, extreme dry and hot events are associated with significant reductions in rice, wheat, and cereal yields in the country.

What causes hot and dry monsoon extremes in India?

The study shows that the hot and dry extremes are tied to El Niño as well as Indian Ocean warming.

For example, India experienced seven (1951, 1972, 1979, 1987, 2009, 2014, and 2015) concurrent hot and dry monsoon seasons during  1951–2018. Out of these, four occurred after 1980 while three (2009, 2014, and 2015) occurred recently over the time period of (2009–2018) indicating an increased frequency of such events in recent years.

All these concurrent hot and dry monsoon extremes occurred during El Niño events, the positive phase of ENSO.  Out of the seven hot and dry monsoons, three (1972, 1987, and 2015) were linked to strong El Niño events . Each event induced intense warming and drying across large parts of India with a large part of western and central India experiencing extreme dryness and heat for example in 1987, when SST patterns in the Pacific Ocean were characterised by El Niño conditions.

Extreme hot and dry conditions also prevailed over a large part of northern and central India during the monsoon season of 2009.  The other five hot and dry extreme years (1951, 1972, 1979, 2014, and 2015) were also linked with warm SST anomalies over the central Pacific Ocean and affected large parts of northern India.

How will hot and dry monsoon extremes change in the future?

The study finds that the association of El Niño to concurrent hot and dry extremes is likely to rise by 20 percent over 2071–2100 compared with 1971–2000.

Concurrent hot and dry extremes will increase in frequency and magnitude over the coming century in spite of projected moderate increases in future monsoon rainfall. The rise in surface-air temperatures will conspire with El Niño to yield extreme seasonal heat and dryness.

The frequency of concurrent hot and dry extremes will increase by a factor of 1.5 under continued greenhouse warming during the 21st century

This increased severity of hot and dry monsoon extremes is likely to pose a great challenge to the future food security of the Indian subcontinent, if urgent measures are not undertaken to deal with the situation.

Focus on climate change adaptation through sustainable agricultural practices, better water management through community participation and capacity building and data generation on sustainable agricultural practices can go a long way to help tackle this impending crisis in the  face of climate change in the country.