Q. Which of the following is/are the causes of Urban heat island effect
1. High amount of evapotranspiration
2. Building of skyscrapers
3. Close construction
4. Waste heat from Vehicles, factories
Which of the statements given above is/are correct?

[A] 2 and 4 only

[B] 2, 3 and 4 only

[C] 1, 2 and 3 only

[D] All of the above

Answer: B

A recent report by Climate Trends said that most parts of India experience 12-66 days of potentially deadly heat and humidity combinations in a year. The report also pointed out that the temperature will increase 4.3 degrees Celsius by 2100 relative to pre-industrial temperature. 

Key findings of the report: 

  • Most of India experiences 12-66 days of a combination of potentially deadly heat and humidity, with hotspots along the east coast. 
  • The report warned of a substantial worsening of the situation even by 2050. 
  • The report also warns that in hot conditions, humans cool themselves by sweating; but if the humidity is too high, sweating no longer works, and the human also risks dangerous overheating. 

Causes of Urban Heat Island: 

  • The lack of evapotranspiration in the city leads to the city experiencing higher temperatures than its surroundings. 
  • EvapotranspirationEvaporation involves the movement of water to the surrounding air, and transpiration refers to the movement of water within a plant and a subsequent lot of water through the stomata (pores found on the leaf surface) in its leaves. Grass, plants, and trees in the suburbs and rural areas do this. 
  • Close construction: When houses, shops, and industrial buildings are constructed close together, it can create an Urban Heat Island. Building materials are usually very good at insulating, or holding in heat. This insulation makes the areas around buildings warmer. 
  • Waste heat from vehicles, factories, and air conditioners may add warmth to their surroundings, further exacerbating the heat island effect. 
  • Building of skyscrapers: When there is no more room for an urban area to expand, engineers build upward, creating skyscrapers. All this construction means waste heat—and heat that escapes insulation has nowhere to go. It lingers in and between buildings in the UHI. 
  • Urban haze—The haze of air pollution that hangs over many cities can act as a miniature greenhouse layer, preventing outgoing thermal radiation (heat) from escaping from urban areas. 

Read moreUrban heat island – causes, impact and solutions: Explained, Pointwise