Bring out the causes for the formation of heat islands in the urban habitat of the world. (UPSC 2013)

Heat islands are urban areas that remain warmer than surrounding rural land, especially at night. They form because cities replace natural cover with heat-absorbing surfaces. Asphalt, concrete and dark roofs have low albedo, absorb more solar radiation and release it slowly. Loss of vegetation reduces shade and evapotranspiration. Dense high-rise buildings create urban canyons that trap heat, reduce wind flow and reflect outgoing long-wave radiation. Waste heat from vehicles, industries, air-conditioners and generators further raises temperatures, while air pollution and aerosols hinder heat loss. Thus, built-up density, weak ventilation and human energy use together intensify urban warming.