Question 1
On a summer afternoon, a city can feel several degrees hotter than nearby fields or forests. This "urban heat island" happens because dark roofs and pavement absorb sunlight and radiate it back like a stovetop, while trees and soil release cooling moisture. The heat is more than uncomfortable; it strains power grids as air conditioners run nonstop and can worsen pollution. Some cities test remedies. Replacing asphalt with lighter, reflective materials reduces how much heat is stored. Planting street trees offers shade people can feel immediately. Another strategy is the green roof: shallow soil and hardy plants placed atop buildings. The plants act like tiny sponges, soaking up rain and then letting it evaporate, which draws heat away from the air. In one study, a block with several green roofs measured lower afternoon temperatures and needed less energy to cool homes. While a single roof is not a magic fix, clusters of vegetation create cooler corridors that let breezes move. Even small patches make a difference on the hottest days. In short, adding living surfaces helps cities behave a bit more like the landscapes they replaced, softening extreme heat while also absorbing stormwater and providing pockets of habitat.
What is the central idea of the passage?
- Green roofs are too costly for most buildings to install.
- Cities are hotter mainly because they are crowded with people.
- Adding vegetation and reflective surfaces can help cities reduce extreme heat and provide other benefits.
- Air conditioners are the primary cause of urban heat.