การฟัง TOEFL

🎧 บทถอดเสียง

Narrator: Listen to part of a lecture in an environmental science class. Professor: Today we're going to talk about urban heat islands. As you know, cities tend to be warmer than surrounding rural areas. This is mainly because of the materials we use to build cities—concrete and asphalt absorb and retain heat much longer than natural surfaces like soil and vegetation. Also, the lack of trees means less shade and less evaporative cooling from plants. But there's a lesser-known factor: the waste heat generated by human activities, such as running air conditioners, cars, and industrial processes. Interestingly, a study in Phoenix, Arizona, found that waste heat can account for up to 20 percent of the urban heat island effect, especially at night. So, while we often focus on building materials, we can't ignore the impact of our energy use. That's why some cities are encouraging green roofs and reflective pavements, but also promoting energy efficiency and public transit to reduce waste heat.