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Listen to part of a lecture in an environmental science class. Today we're going to talk about a fascinating phenomenon called 'urban heat islands.' Essentially, cities tend to be warmer than the surrounding rural areas. Why is that? Well, there are several factors. First, concrete and asphalt absorb and retain heat from the sun much more than natural surfaces like soil and vegetation. Second, buildings and roads block wind, reducing natural cooling. Third, human activities—like driving cars and running air conditioners—generate additional heat. But here's an interesting twist: some cities are actually trying to combat this effect through 'cool roofs.' These are roofs painted white or coated with reflective materials. They bounce sunlight back into space, reducing heat absorption. In fact, a study in Los Angeles showed that if all roofs were made reflective, the city's average temperature could drop by about 2 degrees Celsius. That might not sound like much, but over time, it could significantly reduce energy consumption for cooling and even improve air quality. So, you see, urban heat islands aren't just an inevitable consequence of city life—they can be mitigated with smart design.