IELTS Reading: Matching Headings

How cities keep their cool

A  On a hot afternoon, a city can be several degrees warmer than the countryside around it. The reasons are built into the city itself: dark roads and roofs absorb sunlight, there is little vegetation to provide shade or moisture, and cars and air conditioners pump out waste heat. As heatwaves become more frequent, this “urban heat island” effect turns from a discomfort into a health risk, and city governments are under growing pressure to cool their streets.

B  Many cities are betting on street trees. Trees fight the heat in two ways: their leaves block direct sunlight, and they release water vapour, which cools the surrounding air much as sweating cools skin. A mature canopy can make a pavement feel several degrees cooler on a hot afternoon. Some planting programmes now add trees along streets and in parks by the thousand, although saplings take years before they give real shade.

C  Another approach is to make surfaces bounce sunlight back. Painting roofs white, or using reflective coatings and paler paving, means less heat is absorbed in the first place. White-painted houses have kept Mediterranean towns bearable for centuries, and modern “cool roof” materials can lower a building’s roof temperature dramatically on a sunny day. The idea is cheap compared with most measures, although in cooler climates the lost winter warmth has to be considered.

D  When heat becomes dangerous, some cities open cooling centres: public buildings such as libraries and community centres where anyone can sit in air conditioning for free. They are aimed above all at elderly residents, young children and people whose homes have no cooling of their own. During severe heatwaves, which can last for days, opening hours are extended into the evening, and some centres also offer basic health checks, such as blood-pressure measurements.

E  Water is the oldest coolant of all. Fountains, mist sprayers in public squares and shallow channels all cool the air as water evaporates. A few cities have gone further and uncovered streams that were buried in concrete pipes decades ago, bringing them back to the surface, where they lower the temperature of whole streets. Such projects are expensive and take years to plan, but they also bring nature back into the city.

F  Not everyone benefits equally, however. Wealthier districts often have more trees and newer roofs, while the hottest, most crowded neighbourhoods may have neither. Planting programmes take a decade to pay off, and budgets run out long before every street is shaded. For many planners, the real challenge is therefore not inventing new ways to cool a city, but making sure the existing ones reach the people who need them most.