TOEFL Listening

🎧 Listening Transcript

Narrator: 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 asphalt and concrete, which absorb and re-radiate solar energy. Another factor is the lack of vegetation, which normally provides shade and cools the air through evapotranspiration. But there's a less obvious contributor: waste heat from buildings and vehicles. Now, a common solution is planting more trees, and indeed, that helps. However, recent studies suggest that reflective rooftops, or 'cool roofs,' can be even more effective in certain climates. These roofs reflect sunlight and emit absorbed heat more efficiently than traditional dark roofs. But here's the catch: in colder regions, cool roofs might increase heating demands during winter, offsetting some of the summer savings. So, the optimal strategy depends on local climate and building design. The key is to balance summer cooling benefits against winter heating costs.