Practice Tests
IELTS Reading (AC) Task 1 #204

A. An urban heat island (UHI) is a metropolitan area that is significantly warmer than its surrounding rural areas due to human activities. The temperature difference is usually larger at night than during the day and is most apparent when winds are weak. This phenomenon occurs because the materials commonly used in urban construction, such as concrete, asphalt, and brick, absorb and retain more of the sun''s heat than the natural landscapes they replace.

B. Several factors contribute to the formation of urban heat islands. The dark surfaces of roads and roofs have a low albedo, meaning they absorb a high percentage of solar radiation. The lack of vegetation in cities reduces the natural cooling effect of shade and evapotranspiration (the process by which plants release water vapour). Additionally, waste heat generated by sources like vehicles, air conditioning units, and industrial processes adds further warmth to the urban environment. The dense concentration of tall buildings can also trap heat by blocking wind and reducing the rate at which heat radiates away at night.

C. The UHI effect has a range of negative consequences. It increases energy consumption, as higher temperatures lead to greater demand for air conditioning, which in turn increases greenhouse gas emissions and worsens the problem. It can also exacerbate air pollution by accelerating the formation of ground-level ozone. Most importantly, urban heat islands pose a significant risk to public health, increasing the incidence of heat-related illnesses and mortality, particularly among vulnerable populations such as the elderly and low-income communities.

D. Mitigating the urban heat island effect requires a strategic approach to urban planning and design. Key strategies include increasing the amount of green infrastructure, such as parks, green roofs, and street trees. Using "cool" materials with a high albedo for roofs and pavements can reflect more sunlight and reduce heat absorption. Promoting energy efficiency and reducing waste heat emissions are also important components of creating cooler, more liveable, and more sustainable cities.