How to durably cool the concretized and dangerously hot Indian cities?

Over the past month, Rani has been exhausted all the time. As the mercury soared past 42 degrees Celsius in Delhi, living in her tin-roofed, poorly ventilated house made of mud and corrugated iron made it difficult to sleep. With this heat stress, Rani had to give up her daytime cleaning duties. She can only work in one house late at night.

Her only employer, Padma, meanwhile struggles with another set of problems: spiraling electricity bills and the constant struggle to keep her nine-month-old baby comfortable throughout the day.

As was evident this summer, issues like Padma and Rani are becoming commonplace across India. In 2019, of all working days lost globally due to high temperatures, India accounted for 39%.

Experts predict that by 2030, around 34 million full-time jobs will likely be lost to heat. By that year, as construction and other outdoor work will likely become increasingly difficult due to increased heat waves, global gross domestic product is expected to fall by $2.4 trillion. This does not include the pressing costs of public health emergencies to the public purse.

The science is indisputable

In April and May, more than 5,610 Indian urban areas with a cumulative population of 36.4 crore were subjected to very high heat stress – over 38 degrees Celsius on the Universal Thermal Climate Index scale. About 25.4 million people experienced very high heat stress for more than 300 hours, or more than 12 days.

Increasing vehicle emissions and air conditioning use, creeping concretion and loss of natural vegetation are accelerating the creation and exacerbation of the “urban heat island effect”, whereby urbanized areas experience higher temperatures than peripheral areas.

According to a 2014 report from the Indian Institute of Science, the ideal tree-human ratio should be seven trees for each person. The lack of trees increases the risk of exposure to higher temperatures. As a result, conditions are dire for some neighborhoods in east Delhi, such as Mustafabad, which has just one tree for every 487 people in the neighborhood.

Even within neighborhoods, there are temperature variations due to building patterns, lack of vegetation, and different types of roofing materials that usually result from socio-economic differences.

Industrial areas and heavily concreted and compact urban agglomerations, without vegetation or tree-lined avenues, have significantly higher temperatures.

Construction materials, and in particular types of roofing, increase heat absorption. In Mumbai, for example, 1.02 million households use heat-absorbing GI/metal/asbestos sheets for roofing according to 2011 census data.

When combined with poor ventilation and poor orientation and design, it results in prolonged nighttime heat that has serious health consequences.

The human body is unable to cool down and recover from daytime heat exposure, which disrupts sleep patterns and worsens existing health conditions that increase the risk of mortality.

Resilience building

Four long-term sectoral interventions could help mitigate urban heat.

Buildings and energy consumption: Passive design techniques, alternative materials that respect the environment and spatial orientation adapted to climatology should be made mandatory by regulation. Indoor air pollution, which can exacerbate heat, should be reduced by improving cooking fuels. Higher outdoor temperatures lead to increased energy consumption, around 40% coming from heating, ventilation and air conditioning alone, to maintain thermal comfort. All buildings should house energy-efficient appliances and building management systems that enable optimization.

Blue-green infrastructure: Indian cities are woefully insufficient in terms of open green space per capita. Besides increasing porosity and reducing ambient temperature, green spaces also offer health co-benefits. Development plans should set targets for increasing sponge areas and regulations should mandate the development of various urban forest typologies – parks, green roofs – for adaptation benefits. Better management of water bodies and wetlands that promotes good ecological functioning while ensuring sustainable use must be ensured.

Sustainable mobility: Increased automobile pollution and the use of air conditioning coupled with poor street design that provides little or no permeability or natural vegetation exacerbate the heat island effect. The implementation of the national urban transport policy, which prioritizes non-motorized transport and associated infrastructure, as well as quality public transport using cleaner and more efficient fuels, must be accelerated in cities. It also has the added benefit of improving air quality, leading to better health outcomes for everyone.

Waste Management: Dangerous heat islands form in and around landfills. This comes from the production of methane from unsorted waste or landfill fires and pollution from poorly managed sites. Good solid waste management at source, including strict enforcement of segregation and disposal, warrants immediate action in cities. In addition, landfills must be designed and managed scientifically to enable the extraction of methane. Circular economy approaches to construction and demolition waste management can reduce dust causing air pollution.

A collaborative solution

A recent study by the UK’s Met Office estimated that India’s record high temperature period could occur every three years now instead of the previous 312-year period. Without urgent action, 75% of the workforce, i.e. those employed in heat-exposed jobs, and nearly 40% of India’s economy will be vulnerable.

Urban heat management requires all stakeholders to collaborate and co-create sectoral adaptation and mitigation strategies with well-thought-out delivery mechanisms. This can be done by leveraging policies and guidelines to urgently develop and implement comprehensive short- and long-term measures.

Furthermore, the development of human and financial capacities to adopt a systemic approach to the management of urban heat islands is crucial.

Empowering communities and stakeholders to better understand heat waves and undertake data-driven vulnerability assessments, as well as design, fund and implement integrated strategies and actions is the need of the hour.

OP Agarwal is CEO and Jaya Dhindaw is Program Manager for Integrated Urban Development, Planning and Resilience. Raj Bhagat Palanichamy is Senior Geoanalytics Program Manager at World Resources Institute India (WRI India).