India must act now to beat extreme heat

Summer arrived early this year in India, bringing 50 degrees Celsius temperatures in several parts of the country. While India is no stranger to high heat and humidity during the summer months, the climate crisis is causing heatwaves to be longer, more frequent, and more intense. By 2050, parts of India are projected to be too hot in the summer to be habitable. Heat stress can cause a spectrum of health impacts, from reduced productivity to headache, nausea, cramps, increased heart rate to, eventually, heat stroke, organ failure and death. With less than 10% of Indians having access to air conditioning today, there have been several reports of deaths, and thousands have been hospitalised due to heat stroke during the May-June heatwaves.

Humid heat can be more lethal than dry heat as the body is unable to cool down by sweating. The combination of temperature and humidity is captured in the heat index, which gives an indication of “perceived heat stress as experienced by a healthy adult resting in the shade with access to water”. Revised heat index calculations by University of California Berkeley professor David Romps have demonstrated that a temperature of 39 degrees Celsius in conjunction with 70% humidity and above, or 45 degrees Celsius with 45% humidity and above, could result in heat exhaustion, stroke, and even death. In Patna, Bihar, the afternoon of May 30 saw a temperature of 37 degrees Celsius with humidity reaching 80%. These conditions are equivalent to a heat index of 74, when the body’s core temperature begins to rise due to heat retention. And in direct sunlight, the heat index was deadly at 82.

In such conditions, it is critical to protect vulnerable groups such as outdoor manual workers, the homeless, children, the elderly, or those without access to cooling. About half of India’s adult workforce (over 300 million individuals) is engaged in labour-intensive jobs such as agriculture, manufacturing, construction and street vending that involve direct exposure to heat stress. These manual workers are disproportionately affected by the heatwaves and currently are left to fend for themselves. Projections by the International Labour Organization, assuming a conservative global temperature rise of 1.5 degrees Celsius by the end of this century, indicate that India could see a 5% loss to the Gross Domestic Product (GDP) by 2030 due to the impact of heat stress on labour productivity unless measures are taken.

There is sufficient evidence to suggest that the deaths due to heat stress are undercounted, as the cause of death could present as heart attack, kidney failure, etc. Recent research by Jeroen de Bont of the Karolinska Institutet in Sweden and others quantifies additional deaths due to heatwaves across India’s 10 largest cities. They find that two-day heatwaves can cause a bump of 15% in daily average deaths, while a five-day intense heatwave can push up daily deaths by over 30%. This would amount to tens of thousands of additional deaths if an intense five-day heatwave occurred everywhere in India just once during the summer season, making a single intense heatwave the most lethal annual disaster.

Over the last decade, both the Union and several state governments have devised programmes to increase awareness of and deploy early warning systems for heatwaves, as well as enhance the preparedness of public health infrastructure during the summer months. The National Disaster Management Authority (NDMA) has issued guidelines for the prediction and management of heatwaves, based on which 17 states have prepared Heat Action Plans (HAPs) for responding to extreme heat. However, most HAPs fall short on several fronts, including accounting for humid heat, hot nights and urban heat island effects, delineating adequate funding, and long-term infrastructure interventions to prevent heat deaths.

A modified definition of a heatwave to incorporate humidity would be a key first step to quantifying the scale of the problem correctly. A revised heat index that accounts for thermal load from direct exposure to the sun, as well as internal heat generation due to manual labour, should be assessed. The HAPs should be based on heat index projections to prepare for a warmer future. Secondly, a district-level vulnerability assessment to prioritise interventions for high-risk regions is urgently needed. This mapping should include variables such as population density, temperature and humidity patterns, per capita income and the share of the population employed in manual casual work. In the medium-term, HAPs must expand their interventions to include access to cooling shelters. Public spaces such as community centres, schools and libraries, can be fitted with air conditioning and stocked with water and electrolytes for a low-cost upgrade to function as a cooling shelter. For example, in the United States, 80-plus cities have put in place 1,400-plus cooling shelters to protect the vulnerable during heatwaves. In the long-run, creating a network of cooling shelters that use passive cooling methods in times of grid failures would be critical.

Long-term interventions have to combine regulatory measures with local heat resilience and investment in research and development (R&D). For instance, increasing green cover in urban spaces that are suffering from the heat island effect could help assuage the situation. However, cities must select the tree species for planting today that can withstand the projected temperatures 20 years hence and are drought-resistant. Light-coloured concrete or reflective paint on footpaths, roads and building roofs can reduce the ambient temperature during the day and night. Regulatory enforcement would be key as landlords are unlikely to invest on their own for the benefit of tenants and renters. Lastly, attention is also needed in urban slums where roofing materials such as corrugated galvanised iron sheets create oven-like conditions inside the informal settlements. Modular roofing slabs made of agricultural and packaging waste can help reduce indoor temperatures by over 5 degrees Celsius.

Institutions and the public infrastructure in India are not ready for the monstrous beast of extreme heat that will mark the climate crisis. The government needs to prioritise the allocation of the R&D budget for developing, validating and disseminating creative and cost-effective solutions to minimise loss of life, productivity, and GDP due to heat stress and other impacts of the climate crisis. Significant investment in institutional preparedness and adaptive measures are urgent and critical for India to build resilience to the new grave threats from a warming planet.

Shruti M Deorah and Ashok Gadgil are with the India Energy & Climate Center, University of California, Berkeley. The views expressed are personal