การฟัง TOEFL

🎧 บทถอดเสียง

Narrator: Listen to part of a lecture in an environmental science class. Professor: Today we're going to talk about an interesting phenomenon called 'urban heat islands.' This occurs when cities are significantly warmer than the surrounding rural areas. Why? Well, one major factor is the materials we use to build our cities—concrete and asphalt absorb and retain heat during the day, and then release it slowly at night. Another factor is the lack of vegetation. Trees and plants provide shade and release moisture through a process called transpiration, which cools the air. In rural areas, you have plenty of vegetation, so the temperature stays more moderate. But in cities, we've replaced those cooling elements with heat-absorbing surfaces. Additionally, human activities—like driving cars, running air conditioners, and using electricity—generate waste heat. All these factors combined can make a city several degrees warmer than nearby rural areas. This has implications for energy use, since people in cities tend to use more air conditioning, which in turn generates more heat, creating a feedback loop. So, what can be done? Some cities are planting more trees, creating green roofs, and using lighter-colored materials to reflect sunlight. These strategies can help reduce the heat island effect.