QUE: What are urban heat islands? Identify the causes behind their formation and discuss measures that can help combat them.

Urban heat islands (UHI) are urban areas that experience higher temperatures than other areas.

•  Structures such as buildings, roads and other infrastructure absorb and emit more heat from the sun than natural land areas such as forests and water bodies.
  
• Urban areas, which are densely populated with such structures and have limited greenery, become “islands” of higher temperatures compared to remote areas.
  
•  It increases energy demand, increases greenhouse gas emissions. It harms human health and also affects the health of flora and fauna.

• Main factors responsible for UHI
  

•  Anthropogenic heat dissipation: Anthropogenic heat sources include cooling and heating buildings, manufacturing activities, transportation and lights. The heat emitted from these sources heats the urban environment through conduction and convection.
  
•  Heat absorption: Surfaces such as roads and parking lots, walls of buildings, absorb solar radiation, which heats the surrounding environment.
  
•  Urban geometry: The height and spacing of buildings affect the amount of radiation received and emitted by urban infrastructure. Tall buildings within many urban areas provide large and multiple surfaces for absorbing sunlight, thus increasing the intensity of urban warming.
  
•  Greenhouse effect: Carbon dioxide (CO2) and other greenhouse gases act as a blanket. Absorbing infrared radiation and preventing it from escaping into outer space.
  
•  Lack of vegetation: The reduction in the amount of natural vegetation in urban areas reduces the natural cooling effect of evaporation.
  
•  Measures to combat UHI:
  
•  Promoting natural vegetation: Natural ventilation is one of the most effective techniques. It can be done by creating ventilated roofs and air-conditioned halls or buildings. Apart from this, the green building approach should be promoted.

•  Use of appropriate materials: Increasing the albedo of the surface has a direct impact on the energy balance of the building. Materials with a high albedo index for solar radiation reduce the amount of energy absorbed and keep the surface cool.
  
•  Use of white pavement instead of asphalt: The temperature of asphalt can reach 63°C and white pavement can reach only 45°C. The lower surface temperature contributes to reducing the temperature of the surrounding air.
  
•  Providing adequate space: Providing adequate space in a building can reduce energy consumption. This prevents buildings from overheating.
  

                            Voluntary initiatives to reduce urban heat islands, such as cool pavement demonstration projects, to policy actions such as building codes, are important. Most mitigation activities have multiple benefits, including cleaner air, improved human health, reduced energy costs, and reduced greenhouse gas emissions. Reducing urban heat islands can also help cities mitigate the effects of climate change.