Nghe TOEFL

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Listen to part of a lecture in an environmental science class. The professor is discussing the concept of urban heat islands. Okay, so we've talked about how cities tend to be warmer than surrounding rural areas. This is called the urban heat island effect. Several factors contribute to this. First, buildings and roads absorb and re-emit solar heat more than natural landscapes do. Second, vegetation is scarce in cities, which means less shade and less cooling through evapotranspiration. Third, waste heat from vehicles and air conditioners adds to the warming. But here's an interesting point: the intensity of the heat island effect varies by time of day and season. It's often strongest at night, because the built environment slowly releases the heat it absorbed during the day, while rural areas cool off more quickly. Also, the effect is more pronounced in winter and in dry climates, where there's less moisture to moderate temperature swings. Now, one potential solution is increasing urban greenery, like planting more trees and creating green roofs. These can lower surface temperatures and improve air quality. However, the effectiveness depends on the scale and design of the green spaces.