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 urban heat islands, a phenomenon where cities are significantly warmer than surrounding rural areas. One major cause is the replacement of natural surfaces with materials like concrete and asphalt, which absorb and re-radiate heat. Another factor is the lack of vegetation, which normally provides shade and cools the air through evapotranspiration. Interestingly, studies have shown that urban heat islands can affect local weather patterns, increasing the frequency of thunderstorms downwind of cities. To mitigate this, cities have adopted strategies like green roofs, which are covered with plants, and cool roofs, which reflect more sunlight. However, these solutions are not equally effective in all climates. In hot, dry regions, green roofs may require excessive irrigation, while cool roofs might be more practical. So, urban planners must consider local conditions when choosing mitigation measures.