การฟัง TOEFL

🎧 บทถอดเสียง

Narrator: Listen to part of a lecture in an environmental science class. Professor: Today, let's talk about the concept of 'urban heat islands.' You might think that cities are just warmer because of all the concrete and asphalt, but it's more complex. The main cause is the replacement of natural vegetation with materials that absorb and retain heat. These materials, like dark roofs and roads, have a lower albedo, meaning they reflect less sunlight and absorb more. Additionally, waste heat from vehicles and air conditioners adds to the effect. Interestingly, the temperature difference between a city and its surrounding rural area can be as much as 5 to 10 degrees Celsius at night, because the city slowly releases the heat stored during the day. Now, one solution is to plant more trees, which provide shade and cool the air through evapotranspiration. Another is to use 'cool roofs' that are painted white or made of reflective materials. These can significantly reduce the heat absorbed. In fact, a study in Los Angeles showed that cool roofs could lower city temperatures by up to 2 degrees Celsius. So, while urban heat islands are a challenge, we have practical measures to mitigate their effects.