Nghe TOEFL

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Listen to part of a lecture in an environmental science class. Professor: Today we're going to talk about a fascinating phenomenon called 'urban heat islands.' Now, cities tend to be warmer than surrounding rural areas, sometimes by as much as 5 to 10 degrees Fahrenheit. Why is that? Well, several factors contribute. First, concrete and asphalt absorb and retain heat from the sun during the day, and then release it slowly at night, so the city doesn't cool down as much as the countryside. Second, buildings block wind, reducing natural cooling. Third, there's less vegetation in cities, which means less shade and less evapotranspiration—that's the process where plants release water vapor, which cools the air. Finally, human activities, like driving cars and running air conditioners, generate waste heat. So, the combination of all these factors creates a localized warming effect. Interestingly, some cities are trying to combat this by planting more trees on rooftops and painting roofs white to reflect sunlight, which can significantly lower temperatures in dense urban areas.