Nghe TOEFL

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Narrator: Listen to part of a lecture in an environmental science class. Professor: Today we're talking about urban heat islands, where cities are significantly warmer than surrounding rural areas. This happens because concrete and asphalt absorb and re-radiate heat, while vegetation, which cools through evapotranspiration, is scarce. One solution is green roofs—rooftops covered with plants and soil. They insulate buildings, reducing energy use for air conditioning. But there's a catch: green roofs require substantial maintenance, including watering and weeding, which can be costly. Another approach is cool roofs, which are painted with highly reflective materials to bounce sunlight back into the atmosphere. Cool roofs are cheaper and require little upkeep, but they don't provide the same insulation in winter, and they may not last as long in harsh climates. Recent studies suggest that a combination—partially green, partially cool—might offer the best balance, though more research is needed on optimal ratios and regional adaptability.