Even with ‘moderate emissions’, India’s heat is set to get worse

Both maximum and minimum temperatures are expected to increase more in the northern states than in the southern states.

Updated - March 06, 2023 10:57 am IST

Published - March 06, 2023 10:30 am IST

The climate crisis is no longer a distant event that might happen in the future. It is here, bringing new and previously unimaginable challenges. Temperatures are rising, rainfall patterns are shifting, and extreme events such as record-high temperatures and heavy rainstorms are becoming more common.

This year in India, the month of February was the hottest so far since 1901. According to a study in The Lancet, published in July 2021, with two decades of data (2000-2019), more than five million people died on average each year worldwide because of extreme temperatures. The Sixth Assessment Report of the Intergovernmental Panel on Climate Change states that extreme heat events will grow with increasing global warming and that every increment of warming matters.

A warmer world we live in

A study by the Centre for Study of Science, Technology and Policy (CSTEP) on the historical climate in India shows that temperature in India has been steadily increasing during both summer and winter. (The author is affiliated with CSTEP.) The recorded increase in maximum and minimum temperature over 30 years (1990-2019) is up to 0.9º C and 0.5º C, respectively.

Summer temperatures have increased by 0.5º C to 0.9º C in many districts in Punjab, Haryana, Uttarakhand, Uttar Pradesh, Bihar, Rajasthan, Gujarat, and the Northeast. Likewise, winter temperatures have also increased by 0.5º C to 0.9º C in 54% of India’s districts, with higher levels of warming in the northern states compared to the southern states.

This increasing heat is a cause of suffering and death in extreme cases. It undermines systems such as agriculture and other climate-sensitive sectors that support the livelihoods and well-being of people and impacts the built environment. 

A joint report by the International Federation of Red Cross and Red Crescent Societies (IFRC), the United Nations Office for the Coordination of Humanitarian Affairs, and the Red Cross Red Crescent Climate Centre on preparing for heatwaves states that an extreme-heat event that was likely to happen only once in every 50 years without the influence of humans on climate is now likely to happen five times with human-induced climate change in the same period. If the warming is under 2º C, such events will occur 14 times; if the warming is kept only under 4º C, they will occur almost 40 times.

How much hotter can it get?

Climate projections for the districts of India by the CSTEP study for a 30-year period of 2021-2050 show that the summer maximum temperature will increase even under a ‘moderate emissions’ scenario. The increase is higher under higher emissions scenarios: likely to be greater than 2º C and up to 3.5º C in over 100 districts and 1.5-2º C in about 455 districts.

That’s not all. Even winter minimum temperatures are projected to increase by 0.5º C to 3.5º C in the future. While the highest warming of 2.5º C to 3º C is projected in fewer than 1% of the districts, an increase by 1º C to 1.5º C is projected in about 485 districts.

It is clear that both summer maximum and winter minimum temperatures will increase in the future. This can affect the growth of plants, ecological systems, and even the carbon economy as the extreme variations in temperature between days and nights will affect the quality of the soil.

The diurnal temperature range (DTR) – the variation between high air temperature and low temperature during a single day – is also changing. A December 2020 study supported by the Department of Science and Technology reported an alarming decline in DTR between 1991 and 2016 over the north-west, parts of the Gangetic plain, and central India agro-climatic zones. This decline signifies an asymmetric increase in the minimum temperature compared to the maximum, which in turn increases the risk of heat stress. This also leads to drought, crop failure, and higher morbidity and mortality.

The joint report by IFRC and others also states that in the near future, heat waves could meet and surpass the human threshold to withstand them physiologically and socially, leading to large-scale suffering, death, and migration. From an urban perspective, the combined effects of warming and urbanisation will cause a significant increase in the number of people at risk of extreme heat.

According to a 2019 International Labour Organisation report, India is expected to lose 5.8% of working-hours in 2030 due to heat stress. The loss in the agriculture and construction sectors will be 9.04%, which in absolute terms translates to 34 million full-time jobs. The July 2021 study suggests that future death rates caused by extreme heat could be staggeringly high by the end of the century, which is comparable in magnitude to all cancers or all infectious diseases.

The time to act is now

More than ever, it is imperative that states step up and share responsibility with other stakeholders to implement the Sendai Framework for Disaster Risk Reduction through improved early warning systems, creation of public awareness, and formulation of heat action plans.

In addition, we also need to consider innovative strategies to combat extreme heat, such as emergency cooling centres (similar to the ones in Toronto and Paris); survival guides that are strategically displayed to survive extreme heat or heat waves (like in Athens); white roofs (Los Angeles); green rooftops (Rotterdam); self-shading tower blocks (Abu Dhabi); and green corridors (Medellin).

But most of all, it is crucial we prepare district-level heat hotspot maps so that different departments of a State and/or district can design long-term measures to reduce deaths due to extreme heat.

Indu K. Murthy is a Principal Research Scientist heading the Climate, Environment and Sustainability Sector at the Center for Study of Science, Technology and Policy (CSTEP), a research-based think tank.

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