Today in our environmental science lecture, we'll discuss urban heat islands. Cities tend to be warmer than surrounding rural areas because of concrete and asphalt absorbing sunlight. One surprising factor is that the lack of trees increases heat, but also, the shape of buildings can trap heat. For instance, narrow streets with tall buildings create canyons that prevent wind from cooling surfaces. Interestingly, painting rooftops white has been shown to reduce local temperatures by up to 2 degrees Celsius. However, this method works best in dry climates, as humidity can reduce its effect. Now, let's look at some case studies from different cities.
❓ According to the lecture, what condition makes white rooftops most effective?
A. A. In cities with tall buildings and narrow streets