How can India’s concretised, dangerously hot cities be cooled down sustainably?
Over the past month, Rani has been exhausted all the time. As the mercury has soared beyond 42 degrees Celsius in Delhi, life in her tin-roofed, poorly ventilated home made from mud and corrugated iron has made it difficult to sleep. With this heat stress, Rani has had to give up her day-time cleaning jobs. She is able to work only at one house late in the evening.
Her sole employer, Padma, meanwhile, is contending with a different set of problems: escalating power bills and the constant struggle to keep her nine-month-old infant comfortable through the day.
As was evident this summer, problems of the sort faced by Padma and Rani are becoming common across India. In 2019, of all the days of work lost globally on account of high temperatures, India accounted for 39%.
Experts predict that by 2030, an estimated 34 million full time jobs likely to be lost to heat. By that year, as construction and other outdoor labour are likely become increasingly difficult due to increasing heatwaves, the global gross domestic product is likely to fall by $2,400 billion. This does not include pressing public health emergency costs to the exchequer.
The science is indisputable
During April and May, over 5,610 Indian urban areas, with a cumulative population of 36.4 crores, were subject to very strong heat stress – more than 38 degrees Celsius in the scale of Universal Thermal Climate Index. About 25.4 crore people faced very strong heat stress for more than 300 hours, or more than 12 days.
Increased vehicular emissions and air conditioning usage, rampant concretisation and loss of natural vegetation accelerates the creation and exacerbation of the “urban heat island effect”, by which urbanised areas experience higher temperatures than outlying areas.
According to a 2014 Indian Institute of Science report, the ideal tree-human ratio should be seven trees for every person. The lack of trees increases the risk of exposure to higher temperatures. As a result, conditions are extreme for some East Delhi wards, such as Mustafabad, which have just one tree for every 487 people in the ward.
Even within neighborhoods, there are temperature variations due to building patterns, lack of vegetation, and different roofing material types that typically arise from socio-economic differences.
Industrial areas and heavily concretised, packed urban settlements, without vegetation or tree lined avenues, have significantly higher temperatures.
Building materials, and in particular roofing types, heighten heat absorption. In Mumbai, for instance, 1.02 million households use heat-absorbent GI/Metal/Asbestos sheets for roofing according to data from the 2011 Census.
When coupled with poor ventilation, and improper orientation and design, it results in prolonged night-time heat that has dire health implications.
The human body is not able to cool down and recover from daytime heat exposure, disrupting sleep patterns and aggravating existing health conditions that raise mortality risk.
Four long-term sectoral interventions could help mitigate urban heat.
Buildings and energy use: Passive design techniques, alternate environmentally friendly material and climatologically suited spatial orientation should be mandated by regulation. Indoor air pollution, which can exacerbate heat, should be reduced by improving cooking fuels. Higher outdoor temperatures lead to increased energy use, about 40% from heating, ventilation, and air conditioning alone, to maintain thermal comfort. All buildings should house energy efficient appliances and building management systems that allow optimisation.
Blue-green infrastructure: Indian cities are woefully inadequate in terms of per capita green open spaces. In addition to increasing porosity and ambient temperature reduction, green spaces also provide health co-benefits. Development plans should set targets to increase sponge surfaces and regulations should mandate the development of various typologies of urban forests – parks, green roofs – for adaptation benefits. Better management of water bodies and wetlands that promotes proper ecological functioning while still providing sustainable usage should be ensured.
Sustainable mobility: Increased vehicular pollution and the use of air-conditioning coupled with improper street design that offer little or no permeability or natural vegetation exacerbates the heat island effect. Implementing the National Urban Transport Policy, which prioritises non-motorised transport and associated infrastructure, along with high-quality public transport that uses cleaner and efficient fuels, needs to be accelerated in cities. This also has the co-benefit of improved air-quality that leads to better health outcomes for all.
Waste management: Dangerous heat islands form in and around landfills. This arises from methane production from unsegregated waste or landfill fires and pollution from poorly managed sites. Proper solid waste management at source, including strict enforcement of segregation and disposal, warrants immediate action in cities. In addition, landfills need to be designed and managed scientifically enabling methane extraction. Circular economy approaches to construction and demolition waste handling can reduce dust causing air pollution.
A collaborative solution
A recent study by the United Kingdom’s Met Office assessed that the spell of record-breaking temperatures in India may occur every three years now instead of the previous time frame of 312 years. Without urgent action, 75% of the labour force, namely those employed in heat-exposed work, and nearly 40% of India’s economy will be left 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 both short and long term comprehensive measures.
In addition, developing human and financial capacity, to take a systems approach to urban heat island management, is crucial.
Capacitating communities and stakeholders, to better understand heat waves and undertake data-driven vulnerability assessments, along with designing, financing and implementing integrated strategies and action is the need of the hour.
OP Agarwal is CEO and Jaya Dhindaw is Program Director-Integrated Urban Development, Planning and Resilience. Raj Bhagat Palanichamy is Senior Program Manager-Geo Analytics at the World Resources Institute India (WRI India).