The increase in urban temperatures can be attributed not only to climate change but also to certain urban planning and construction choices
In India, we are witnessing two significant challenges: heavy rains and flooding in certain regions, and the distressing fatalities caused by heat waves in other areas. The long-term trends are pointing to a worrying reality - our cities are steadily becoming hotter due to the ongoing impact of climate change.
High temperatures in cities affect not only human health but also hamper productivity. These challenges do not affect everyone equally. Vulnerable groups, such as the urban poor, women and elderly individuals bear the brunt of heat-related issues due to their unique economic, biological, and physical circumstances. They often lack access to adequate cooling and healthcare, leading to higher mortality rates during extreme heat events.
The temperatures in cities have been getting warmer over the years. Since 1900, the average temperature in India has gone up by 0.7°C, and it is predicted to rise even more, possibly by up to 4.4°C by the year 2100. The increase in urban temperatures can be attributed not only to climate change but also to certain urban planning and construction choices.
Cities are even hotter than the surrounding rural areas, sometimes by as much as 3°C, and this is due to what we call ‘urban heat islands’. This phenomenon occurs due to the abundance of concrete structures and buildings, coupled with lack of green spaces and trees to absorb heat. Additionally, vehicle emissions in crowded city centres contribute to local heat generation. The rapid and unplanned growth of cities has further exacerbated these urban heat islands by encroaching upon natural green cover and wetlands.
While air conditioners provide some respite from the heat, their widespread use also aggravates the problem by increasing greenhouse gas emissions. By 2050, it is estimated that air conditioning in India could contribute up to a quarter of global cooling-related emissions. It is exigent now to turn to sound planning practices and technologies which promise climate-friendly cooling options.
Plan Cool Cities: To address these challenges, a multi-faceted approach is essential. The foundation of cooling in cities should begin with the city's master plans and bylaws. Heatmaps, created using remote sensing and GIS technologies, can help identify areas with significant heat island effects. Urban planners must take these insights into account and design land use patterns that avoid creating such hotspots.
In existing cities, zoning regulations should be leveraged to promote mixed land use and the incorporation of green street designs to enhance cooling. Additionally, regulating building heights through suitable floor-to-area (FAR) or floor space index (FSI) ratios can prevent the construction of uniformly tall buildings that restrict air movement and trap heat.
Cool with Nature: To achieve sustainable cooling, nature-based solutions should be prioritized. Greenery and water bodies not only provide cooling benefits but also contribute to reducing greenhouse gas emissions and supporting biodiversity. National urban planning guidelines, as well as recommendations from the World Health Organization, advocate for a minimum of 10 square meters of open spaces per capita. However, Indian metropolises currently lag with an average of only 2 square meters per person. By mandating green roofs, vertical greenery, and greater provision of open green spaces per capita, cities can begin to overturn this statistic and enhance their heat resilience. Conservation of wetlands and water bodies is also crucial to combat the urban heat island effect.
Construct Heat-Resilient Buildings: When constructing new buildings, integrating natural ventilation, heat-resistant materials, and effective sun shading can significantly reduce indoor temperatures. Moreover, implementing reflective roof finishes, also known as cool roofs, has proven successful in lowering indoor temperatures by up to 2 °C in cities like Ahmedabad and Hyderabad. The adoption of national building energy codes, such as EcoNiwas Samhita and Energy Conservation Building Code, along with the upcoming comfortable housing standard by Pradhan Mantri Awas Yojana, can guide designers and developers in implementing cooling strategies.
Centralise Cooling for Efficiency: For more substantial cooling demands in business districts, airports, and metro rail systems, centralised cooling through highly efficient district cooling systems (DCS) presents a viable option. The DCS in GIFT City, Gujarat, serves as a successful demonstration of this approach, efficiently offsetting the high cooling demand in such areas. Municipalities and development authorities can play a pivotal role in planning and implementing district-level cooling by designating land for central cooling plants and their supporting infrastructure, incentivizing or directing large energy consumers to connect to the DCS, and leveraging municipal land to attract private investment.
Presently, our cities are lacking in crucial aspects of heat mitigation and adaptation. The benchmarking of green cover, green buildings, and water bodies through the ClimateSmart Cities Assessment Framework by the National Institute of Urban Affairs has shown that green cover is limited to 12-15 per cent or less of total area in majority of cities.
By 2050, around 50 per cent of the population is expected to live in urban areas, making it imperative to step up efforts to ensure the health, comfort, and economic productivity of urban life in India. This requires collaborative action from city leaders, policymakers, and citizens to create cooler and more sustainable cities for the future.
(Hitesh Vaidya is Director, National Institute of Urban Affairs (NIUA). The column was co-authored with Aarti Nain, Advisor, NIUA. )