Representative image. Photo: Augustus Binu/Wikimedia Commons, CC BY-SA 2.0
Rains towards the end of the southwest monsoon in India in 2021 were unusual: a very large part of the country experienced the second wettest September since 1994. In eight states in central, western, and northwestern India, the excess rain ranged from 70% above average in Odisha to 268% above the average in Gujarat.
In the previous year, 2020, rains were average or above average in almost the entire country. Going back further, 2014, 2015 and 2016 were marked by generally below-average rains; before that, there were above average rains in 2010, 2011, 2012 and 2013.
Such dry and wet epochs, each lasting several years to a decade, have occurred in the Indian subcontinent for at least the last 700 years. Some of the dry epochs caused mega-droughts, resulting in famines that killed millions of people, and catalysed mass migrations within and out of the subcontinent.
Climate information recorded in trees over the last 300 years, ocean temperature and continental rain data in the last 50 to 100 years, and more recent climate models show that, worldwide, dry/wet epochs are caused primarily in 10-20-year-long decadal cycles in tropical-subtropical Pacific Ocean surface temperatures. These in turn are due to the Interdecadal Pacific Oscillation (IPO) – also known as the Pacific Decadal Oscillation (PDO).
Decadal cycles in tropical-subtropical ocean temperatures are caused by large-scale interactions among winds, ocean currents and waves, and heat and water vapour transfers from oceans to the atmosphere.
In the positive phase of an IPO cycle, the tropical-subtropical Pacific surface temperatures are warmer than average. As a result, there is below-average rain in central, western and northwestern India. In the negative phase of the IPO cycle, there is above-average rain in these regions.
The IPO/PDO was generally in the negative phase of the cycle in the wet epochs (2010-2013 and 2020-2021) and in the positive phase in the dry epoch (2014-2016). The IPO is still in the negative phase of the cycle in 2022, so we should expect the Indian monsoon to be average to above-average.
The IPO’s effects on the atmosphere and Indian monsoon rain also affect crop output, especially in regions of non-irrigated crops. Fifty years’ (1961-2010) worth of data from the UN Food and Agriculture Organisation shows that annual productions of rice, soybean, corn (maize), cashew nuts, orange, millet, cotton, barley and some other major, non-irrigated crops are substantially below average in the positive phases of the IPO, as should be expected.
Apart from people and crops, natural ecosystems also fare poorly in both types of epochs. Especially in dry epochs, millions of milch and draft animals such as buffaloes, cows, goats and camels suffer due to shortages of fodder and forage.
While such consequences of the IPO and other natural variable climate phenomena are bad enough, India’s long-term water quantity and quality situations are truly alarming.
A 2018 report by NITI Aayog stated that India is currently facing its worst water crisis in history, with 600 million people facing high to extreme water stress, and 200,000 people dying every year due to inadequate access to safe water.
The report also stated that by 2030, projected water demand would be double the available supply, implying permanent water scarcity for hundreds of millions of people and a 6% drop in India’s GDP. It pointed to an imminent need to deepen understanding of India’s water resources and use, and for the government to intervene to make water use efficient and sustainable.
But as if this and other projections were not alarming enough, the report overlooked current and projected effects of climate variability and changes in their projections of India’s water situation.
Data from tree rings indicates that the duration and severity of droughts have decreased substantially in the last 100 to 150 years. Since these droughts were caused by natural climatic variations, it seems likely that mega-droughts will return to the Indian subcontinent in future – and will be exacerbated by climate change. Then, there are the projected effects of climate change due to higher concentration of greenhouse gases in the atmosphere.
In light of India’s water situation already being precarious, the government should found and permanently sustain a multidisciplinary and multi-institution programme of research and applications in weather and climate variability; potential effects of climate change; understanding and predicting societal impacts of weather changes; and development of adaptation options for all affected sectors.
Such a programme should have the Government of India as a partner, and should be housed in an academic institution of national and international repute.
This programme will have to address adaptation issues at all levels, from national to local administrative, and must involve stakeholders, government ministries and/or departments, and NGOs in all affected sectors and regions as partners. Finally, and importantly, such a programme must report frequently to the people of the country in languages and idioms they can easily understand.
In the absence of such a programme sustained in this way, India will almost certainly face calamities like the ones in the past – multiplied manifold by the vastly increased scale of human activity, with consequences too catastrophic to contemplate.
Vikram M. Mehta is executive director, Centre for Research on the Changing Earth System (www.crces.org), Clarksville, Maryland.