托福听力

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Listen to part of a lecture in an environmental science class. Today we're going to talk about urban heat islands, a phenomenon where cities are significantly warmer than surrounding rural areas. This happens because buildings, roads, and other infrastructure absorb and re-emit the sun's heat more than natural landscapes do. In addition, cities have less vegetation and fewer water bodies, which would otherwise provide cooling through shade and evaporation. One major consequence is increased energy consumption, as people use more air conditioning during hot days. This, in turn, leads to higher greenhouse gas emissions. Another issue is worsened air quality, since heat accelerates the formation of ground-level ozone. To mitigate these effects, some cities have implemented green roofs, which involve planting vegetation on rooftops. Green roofs not only reduce building temperatures but also absorb rainwater and provide insulation. However, their upfront costs can be high, which may discourage widespread adoption. Still, many experts argue that the long-term benefits outweigh the initial investment, especially as climate change makes heatwaves more frequent and intense.