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Narrator: Listen to part of a lecture in an environmental science class. Professor: Today we're going to talk about urban heat islands. As you know, cities tend to be warmer than surrounding rural areas. This is due to several factors, but one major one is the widespread use of materials like concrete and asphalt, which absorb and retain heat during the day and release it slowly at night. Another factor is the lack of vegetation, which normally provides shade and cools the air through evapotranspiration. So, how can we mitigate this effect? One common strategy is planting more trees and creating green roofs. But there's also a lesser-known approach: using reflective or 'cool' roofing materials that reflect more sunlight. A study in Los Angeles found that increasing the albedo of rooftops across the city could reduce peak summer temperatures by up to 2 degrees Celsius. However, this method has limitations. Reflective roofs are most effective in hot, sunny climates, and they may not be as useful in colder regions where heating is more of a concern. Also, they don't address the heat trapped at street level. So, a combination of strategies is often recommended.