Subject: Environment & Ecology

India's capital Delhi recorded its highest-ever temperature of 49.2°C in 2022, highlighting the growing concern of Urban Heat Islands (UHIs). The phenomenon, where urban areas experience significantly higher temperatures than surrounding rural regions, has become a critical environmental challenge globally.

Causes of Urban Heat Island Formation

1. Anthropogenic Activities and Infrastructure

• Dense Built Environment: Concentration of buildings and infrastructure reduces natural ventilation and traps heat.
• Building Materials: Usage of heat-absorbing materials like asphalt and concrete that retain heat and increase surface temperatures.
• Industrial Activities: Release of waste heat from industrial processes and air conditioning systems contributes to local temperature rise.

2. Reduction in Natural Cooling Mechanisms

• Deforestation: Removal of urban vegetation reduces natural cooling through evapotranspiration.
• Loss of Water Bodies: Destruction of natural water bodies eliminates their cooling effect on surrounding areas.
• Decreased Albedo: Replacement of natural surfaces with dark materials reduces the reflection of solar radiation.

3. Urban Design and Planning

• Building Density: High-rise buildings create "urban canyons" that trap heat and restrict air circulation.
• Impervious Surfaces: Increased concrete and asphalt coverage leads to reduced water infiltration and evaporation.
• Studies show 0.5% to 5% energy demand increase for each 1°C temperature rise in urban areas.

4. Transportation and Energy Use

• Vehicle Emissions: Heat generated from vehicular traffic contributes to temperature rise.
• Air Conditioning: Widespread use of cooling systems creates a feedback loop, increasing outdoor temperatures.
• Research indicates 10% to 120% increase in cooling energy consumption in urban areas.

5. Climate Change Amplification

• Global Warming: Rising global temperatures intensify the urban heat island effect.
• Synergistic Effects: Interaction between climate change and urban heat islands creates compound warming impacts.

The Mission Million Trees initiative in Ahmedabad demonstrates how increased green cover can effectively reduce urban temperatures. Such nature-based solutions, combined with sustainable urban planning and climate-responsive architecture, are essential for mitigating the urban heat island effect and creating resilient cities for the future.