TOEFL 듣기

🎧 듣기 원문

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 retain heat. Another factor is the lack of vegetation, since trees provide shade and release moisture through transpiration. But here's an interesting twist: some cities are now experimenting with 'cool roofs'—these are roofs painted white or coated with reflective materials. They can reduce rooftop temperatures by up to 50 degrees Fahrenheit, which in turn lowers the demand for air conditioning inside buildings. However, a recent study in London found that while cool roofs lower indoor temperatures, they can actually increase air temperatures at street level, because they don't release heat back into the atmosphere but instead reflect it downward. This paradox has led city planners to consider a combination of green roofs, which are covered with plants, and cool roofs, since green roofs absorb rainwater and provide insulation but are less effective at reflecting heat. So, the choice of roofing strategy depends on local climate and building density.