When Delhi’s Mungeshpur automatic weather station beeped an unprecedented heat peak of 52.9 degrees on May 29, it provoked an incredulous reaction. Is this an outlier, an anomaly?
The Mungeshpur figures were later ascribed to a technological fault. But the story is not about only one number this summer, but about the consistent long-term rise in the summer heat index (high temperature combined with growing relative humidity) in Delhi, signaling an altered reality. This new normal is evident in the recent analysis of six megacities carried out by the Center for Science and Environment (CSE) which indicates growing heat stress in urban centers of the country due to rising air temperature, relative humidity and land surface temperature. Nights are not cooling down adequately any more. This intensifies thermal discomfort and increases the disease burden.
Several factors are at play. The continuous expansion of the built-up area is increasing heat-trapping concrete surfaces in urban areas. Illustratively, Delhi’s built-up area has increased from 31.4 per cent in 2003 to 38.2 per cent in 2022, and that of Bengaluru from 37.5 per cent to 71.5 per cent in 2023.
Most urban development projects do not meet the minimum requirement of 9 sq m of green space per individual with an ideal urban green space of 50 sq m per capita, as recommended by the World Health Organization. It varies between 1.4 sq m in Pune to 6.67 sq m in Jaipur and 10.41 sq m in Delhi. The green cover is disappearing quickly.
The spatial spread of greenery and the quality of the canopy also matter. The CSE study found that unshaded areas have a land surface temperature (LST) greater than 40°C; Areas shaded by palm trees have a high LST of 35.9°C, while dense foliage-covered areas have a lower LST of 29.7°C. But this science rarely informs on-ground action.
Equally worrying is the disappearing waterbodies. Between 1999 and 2021, Delhi lost half of its surface water; Pune lost 31.8 percent of its surface water, and Jaipur, 21.5 percent of its surface water. This is when we know that water-sensitive urban design can reduce ambient temperatures by 3-8 degrees in a microclimate.
Not many are aware of the added top-up heat from vehicle tailpipes, industrial processes and air conditioning in buildings. There is little clarity about policy action on these heat generators.
The growing heat risk and urban heat island effect have massive equity impacts. The urban maps of heat hotspots overlay snugly with the maps of areas where poor people live. The poor are more vulnerable, given their underlying diseases and patterns of unprotected exposures.
The elderly and children are hugely vulnerable as well. Globally, as per the estimates of the ‘2023 Lancet Countdown and Health and Climate Change’, heat-related deaths among the elderly are expected to increase by 370 percent by mid-century.
The Intergovernmental Panel on Climate Change warns that even if global warming is stabilized at 1.5°C, the frequency and intensity of heat extremes and duration of heat waves will keep rising; and urban growth will further amplify this impact.
Transform urban microclimate
Climate change may be a constant. However, for resilient cities, responsive policies are needed to strengthen the coping and adaptive capacity of the urban population.
Cities have begun framing heat action plans. Despite including longer-term systemic changes to reduce heat risks, in practice, these remain largely fixated on emergency response during heat waves. This focus on advisory to the people, improving drinking water availability in public places, creating more shades and sprucing up health care services to reduce heat-related disease burden among others.
These plans are yet to mature and acquire a legal and funding backup to have an enforceable legal mandate for heat management to reduce the overall thermal load on urban infrastructure and built structures. There are several regulatory instruments in place related to urban resource management, land use, thermal comfort and energy efficiency in built structures, that are not leveraged adequately.
These include environmental impact assessment for buildings and townships, urban and regional development plans formulation and implementation (URDPFI) and urban master plans, energy conservation building codes and Eco Samhita — the building code for energy efficient and thermally comfortable buildings and material — provisions of the Cooling Action Plan, transit-oriented development policies and a series of Indian standards on siting and layout of buildings, natural ventilation.
Yet these remain suboptimal in delivering on heat management indicators. The weakest link is the lack of mandate and monitorable performance and compliance framework to make these policies work on the ground to change the microclimate.
Undo heat traps
Planning needs to go much deeper than the immediate emergency or disaster response to specific heat episodes. This needs sustained action throughout the year to heatproof the city. Ensure land-use changes to expand the green areas and water bodies for a stronger cooling effect. Increase shaded areas.
This requires a mandate for a comprehensive heat vulnerability mapping of cities, auditing the thermal performance of built structures and materials, and identifying vulnerable groups and their access to services and resources. It is equally important to build climate data platforms that focus on ambient heat, surface heat absorption, land surface temperatures, relative humidity, and changing land-use to inform corrective action.
Decisively aligning and augmenting performance-linked funding across sectors is also imperative to enable the implementation of the plans. Cooling action is needed urgently to improve the overall adaptive thermal comfort and prevent the lock-in of urban heat traps in a changing climate.
The writer is Executive Director at Center for Science and Environment