How can India’s tangy and dangerously hot cities be sustainably cooled?

For the past month, Rani has been exhausted all the time. With the mercury level soaring above 42 degrees Celsius in Delhi, life in her poorly ventilated tin-roofed house made of mud and corrugated iron made it hard to sleep. With this heat stress, Rani had to give up day cleaning jobs. She can only work in one house in the late evening.

Meanwhile, her only employer, Padma, faces a different set of problems: spiraling electric bills and the constant struggle to keep her nine-month-old baby comfortable all day.

As was evident this summer, problems of the kind faced by Padma and Rani have become common across India. In 2019, of all working days lost globally due to rising temperatures, India accounted for 39%.

Experts predict that by 2030, an estimated 34 million full-time jobs will likely be lost due to the heat. By that year, as construction and other outdoor work is likely to become increasingly difficult due to increased heat waves, global GDP is likely to decline by $2,400 billion. This does not include the urgency of the costs of the public health emergency on the Treasury.

The science is indisputable

During the months of April and May, more than 5,610 Indian metropolitan areas, with a cumulative population of 36.4 crores, were subjected to extremely extreme heat stress – more than 38°C on the Global Thermal Climate Index scale. About Rs 25.4 crore experienced very strong thermal stress for more than 300 hours, or more than 12 days.

Increased vehicle emissions and air conditioning use, rampant concrete formation and loss of natural vegetation are accelerating the creation and exacerbation of the “urban heat island effect,” where urban areas experience higher temperatures than remote areas.

According to a 2014 Indian Institute of Science report, the ideal tree-to-tree ratio should be seven trees per person. Lack of trees increases the risk of exposure to higher temperatures. As a result, conditions are harsh for some East Delhi wards, such as Mustafaabad, which have only one tree for every 487 people in the ward.

Even within neighborhoods, there are temperature differences due to building patterns, lack of vegetation, and different types of roofing materials that typically arise from social and economic differences.

Industrial areas and heavily congested urban settlements, which have no vegetation or tree-lined roads, have much higher temperatures.

Building materials, especially roofing types, 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 improper routing and design, it results in prolonged nighttime heat that has severe health effects.

The human body is unable to cool off and recover from exposure to heat during the day, which disrupts sleep patterns and exacerbates existing health conditions that increase the risk of death.

building resilience

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

Buildings and Energy Use: Passive design techniques, alternative environmentally friendly materials, and climate-appropriate spatial orientation must be mandated by regulation. Indoor air pollution, which can exacerbate heat, must be reduced by improving cooking fuels. Higher outdoor temperatures increase energy use, about 40% of HVAC alone, to maintain thermal comfort. All buildings must have energy-efficient appliances and building management systems that allow for improvement.

Blue and Green Infrastructure: Indian cities are totally inadequate in terms of per capita open green space. In addition to increasing porosity and reducing ambient temperature, green spaces also provide joint health benefits. Development plans should set targets for increasing spongy surfaces and regulations should mandate the development of different types of urban forests – parks and green roofs – for adaptation benefits. Better management of water bodies and wetlands that promotes sound environmental performance while providing sustainable use must be ensured.

sustainable mobility: Increased vehicle pollution and use of air conditioning along with improper design of streets with 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, along with high-quality public transport that uses cleaner and more fuel efficient, must be accelerated in cities. This also has the co-benefit of improved air quality which leads to better health outcomes for everyone.

Waste Management: Dangerous heat islands form in and around landfills. This arises from methane production from uninsulated waste or landfill fires and pollution from poorly managed sites. Proper management of solid waste at source, including strict application of separation and disposal, requires immediate action in cities. In addition, landfills must be designed and managed in a scientific way that enables methane extraction. A circular economy approach to dealing with construction and demolition waste can reduce dust that causes air pollution.

collaborative solution

A recent study by the UK Met Office estimated that a record temperature wave in India could occur every three years now instead of the previous time frame of 312 years. Without urgent action, 75% of the workforce, specifically those engaged in heat-prone work, and nearly 40% of India’s economy will remain at risk.

Urban heat management requires all stakeholders to collaborate and participate in creating sectoral adaptation and mitigation strategies with well-thought-out delivery mechanisms. This can be done by utilizing policies and guidelines to rapidly develop and implement comprehensive short and long-term measures.

In addition, the development of human and financial capacities, to take a systems approach to urban heat island management, is critical.

Enabling local communities and stakeholders to better understand heat waves and conduct data-driven vulnerability assessments, along with designing, financing and implementing integrated strategies and actions is the need of the hour.

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

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