托福听力

🎧 听力原文

Listen to part of a lecture in an environmental science class. Professor: Today we're going to talk about urban heat islands. This phenomenon occurs when cities are significantly warmer than surrounding rural areas. Why? Well, one major factor is the materials we use to build our cities. Concrete and asphalt absorb and retain heat much more than natural surfaces like soil or vegetation. During the day, these materials soak up solar radiation, and at night, they slowly release that heat, keeping the city warm. Another factor is the lack of vegetation. Trees and plants provide shade and release moisture through a process called evapotranspiration, which cools the air. But in cities, we've replaced many green spaces with buildings and roads. Also, human activities—like driving cars, running air conditioners, and operating factories—generate waste heat. This adds to the overall temperature. So, when you combine these factors, it's no surprise that a city can be several degrees warmer than the countryside around it. Now, there are strategies to mitigate this effect, such as planting more trees, using reflective roofing materials, and creating green roofs. But we'll discuss those solutions next class.