25 February 2025 : Daily Answer Writing

MAINS MODEL QUESTION: 24th FEBRUARY 2025

Q1) Urban heat islands (UHIs) have become a significant phenomenon in Indian cities, exacerbating the frequency and intensity of heat waves. Analyse the underlying factors contributing to this phenomenon and critically assess the existing mitigation strategies. (15 marks, 250 words)

ANSWER

An urban heat island (UHI) is described as a metropolitan area that experiences significantly higher temperatures compared to its surrounding areas. This phenomenon arises from the transformation of natural landscapes into urban environments dominated by concrete, asphalt, and buildings, these absorb and retain heat from the sun much more effectively than vegetation or soil.

Unlike rural areas where heat readily escapes at night, UHIs trap this thermal energy, leading to persistently warmer temperatures in cities. More than 2/3rd of residents in the cities experience at least 40 degrees celsius on an average.

UHI have become a significant phenomenon in Indian cities due to the following

factors:

1. City Material Trap Heat: Concrete and asphalt has negligible albedo unlike natural surfaces. Such materials are being used on a large scale in the Indian cities owing to their easy availability.
2. Tall Buildings: Sky scrapers act as giant walls, trapping heat radiating from surfaces. This is also called the “urban canyon effect”, as it blocks winds from cooling the surface.
3. Limited Cooling Elements: The cooling elements like lakes, parks, etc. are being replaced by asphalt and concrete based buildings and structures.
4. Deforestation: The clearing of forests and reduction of green spaces for urban development diminish the natural cooling effects provided by trees and plants.
5. Vehicle Emissions: The high density of vehicles in Indian cities contributes to heat through exhaust emissions and the heat generated by engines. Traffic congestion in cities like Mumbai and Delhi not only contributes to air pollution but also increases ambient temperatures.
6. Air Conditioning and Electrical Appliances: The widespread use of air conditioners and electrical appliances in urban areas releases heat into the surrounding environment.
7. Tropical Climate: Many Indian cities are located in tropical and subtropical regions, naturally experiencing high temperatures and humidity levels. This is one of the supporting factors of increased UHIs.
8. High Population Density: The rapid population growth and high density in Indian cities increase the demand for housing, transportation, and energy, all contributing to the UHI effect.

THE EXISTING MITIGATION STRATEGIES HAVE THE FOLLOWING

SUCCESSES AND ISSUES

2. Increasing Tree Canopy and Vegetation Cover: This strategy increases the overall green cover in the cities. They also provide shade, reduce surface and air temperatures and facilitate evapotranspiration process which cools down the surface. However, there have been consistency issues and maintenance problems associated with these green covers which leads to abandonment of such areas. Most of the vertical gardens failed in Delhi.
3. Green Roof Implementation: Though such green roofs act as reflective surfaces, the adoption has been poor due to initial capital costs and lack of incentives. Moreover, the overall aesthetics of buildings become poor with implementation of green roofs.
4. Coatings: Cool roof coatings employ high solar reflectance to deflect sunlight and heat from buildings. They also reduce roof surface temperatures, lowering surrounding air temperature. However, there are possibilities of air pollution and water pollution as the chemicals can penetrate in the surroundings. Sometimes such chemicals react with the environment to form VOCs.
5. Renewable Energy: Though the focus has shifted towards adoption of renewable energy, the demand for cooling systems overburdens the energy sources and pushes towards conventional fossil-based power generation. For example, recently Delhi touched peak electricity demand in the last 75 years.
6. Restoration of Water Bodies: Due to overcrowding of spaces in cities, the wetlands and floodplains are being encroached and efforts for conservation and restoration have miserably failed. For example, the death of several crucial wetlands like Kanwar Lake.
7. Vehicular Pollution: Public transport infrastructure in many cities is still inadequate, leading to continued reliance on private vehicles.

WHAT CAN BE DONE?

URBAN PLANNING

1. Integrated Green Infrastructure: All urban infrastructure should be made green instead of working in silos. For example, with construction of parks, green roofing, wetland restoration, etc. should be undertaken. This happened in Singapore’s Comprehensive Green Strategy Program.
2. Energy Efficiency Requirements: Public spaces and offices should be energy efficient. For example, California’s Title 24.
3. e-Transportation: e-Transportation improves the overall condition of pollution contributing less to UHIs.

4. Water Bodies: They have high heat absorption capacity; their high

thermal inertia may limit nighttime cooling.

5. Wind Path Designing: Proper urban design can promote natural

ventilation by creating wind paths through strategic building placement.

POLICY REFORMS

1. Building Codes: There should be established codes for building construction which involves usage of reflective material, less absorbing materials and green roofing.
2. Community Management: The overall monitoring should involve communities living in the area so as to ensure public participation.
3. Monitoring and Mapping: The overall assessment of temperatures of plants, and surrounding red spot areas should be done to differentiate between neighbouring areas. For example, NASA’s Ecosystem Spaceborne Thermal Radiometer Experiment (ECOSTRESS)
4. Green Vegetation: Planting trees and other vegetation is a highly effective strategy. Plants shade surfaces, reduce CO2, and cool the air through evapotranspiration. However, careful planning is needed to avoid hindering natural air flow.
5. High-Albedo Public Infrastructure: Similar to cool roofs, lighter pavements reflect sunlight and reduce heat absorption. Therefore, new Government buildings and offices should adopt lighter pavements. These pavements also allow water to infiltrate the ground, promoting  evapotranspiration and lowering pavement temperature.

6. Mission Mode: To address UHI, the citizens should be made aware of the conditions and promoted to adopt an energy efficient and cooling-inducing lifestyle. For example, Mission LiFE promotes low energy usage. Comprehensive and inclusive urban planning, supported by strong policy frameworks and community participation, is essential for creating resilient and sustainable urban environments in the face of rising temperatures and climate change.