In the reader, tap any word or sentence to hear it in English,
translate it, or look up a definition.
Words to know
noticeably
in a clear way that is easy to see or feel
blacktop
a hard black surface used to pave roads
conditioner
a machine that cools the air in a room
intensify
to make something stronger or more severe
hurricanes
very powerful ocean storms with strong winds
tornadoes
violent spinning windstorms shaped like funnels
reflective
sending light back instead of soaking it up
districts
separate areas or sections of a city
A On a calm summer evening, the center of a large city can feel noticeably warmer than the farmland just beyond its edges. Scientists call this contrast the urban heat island effect. Luke Howard, who kept careful weather records, first described it in the 1810s. He compared temperature readings taken inside London with readings from the nearby countryside, and he found that the city stayed warmer, above all at night. Modern measurements confirm the pattern he observed. On clear, windless nights, the air in a dense downtown can be several degrees Celsius hotter than the air in rural areas close by, and in the largest cities the gap can pass 10 degrees.
B The extra heat has three main sources. First, dark surfaces such as asphalt roads and tar roofs soak up most of the sunlight that strikes them, and on a hot day the surface of a blacktop road can reach about 60 degrees Celsius. Second, cities make their own waste heat, because every engine, air conditioner, and factory releases warmth into the streets. Third, most city blocks contain few plants. Trees cool the air by casting shade and by giving off water vapor through their leaves, so where concrete replaces green space, that natural cooling is lost. Tall buildings intensify the problem, since they trap warm air in narrow streets and block cooling winds.
C The consequences fall on human health and on energy use. In many years, heat kills more people in the United States than floods, hurricanes, or tornadoes, and a single heat wave in Chicago in 1995 caused more than 700 deaths in one week. Heat islands are strongest after sunset, so people in the city get little relief while they sleep. This raises the danger for the elderly and for those with heart disease. Hot weather also pushes up the demand for air conditioning. That strains power grids and raises household bills, and since much of the power still comes from burning fossil fuels, it adds to the pollution that warms cities even more.
D Two remedies have proved particularly practical: cool roofs and street trees. A roof coated with white or reflective paint sends most sunlight back toward the sky instead of soaking it up, and a program in New York City has coated millions of square feet of rooftops in this way since 2009. Trees work in a different way, for they lower air temperatures through shade and moisture. In Medellín, Colombia, planners created a network of green corridors along roads and waterways, and city measurements indicated that these planted routes cooled the nearby streets by around 2 degrees Celsius.
E City governments also try to measure heat before they fight it. Satellites with heat sensors can map surface temperatures block by block. In dozens of American cities, volunteers have driven set routes with sensors on their cars to record how heat shifts from one neighborhood to the next. The maps often show that the hottest districts are poor areas with the fewest trees, so several cities now plant trees in those streets first. The area around Miami went further: in 2021, Miami-Dade County, which includes the city of Miami, named the world’s first chief heat officer, whose job is to lead the local fight against rising heat.
Exam practice
Exam-style questions written by ESLDesk for practice.
They are not official IELTS or TOEFL questions, and ESLDesk is not affiliated with the exam providers.
True / False / Not Given
Do the following statements agree with the information in the passage?
Choose True if the statement agrees with the passage, False if it
contradicts the passage, or Not Given if the passage does not say.
Luke Howard found that the difference between city and country temperatures was largest during the middle of the day.
Show answer
False — Para A: Howard found the city stayed warmer above all at night, not during the day.
In the largest cities, downtown air can be more than 10 degrees Celsius hotter than the air in the countryside nearby.
Show answer
True — Para A: in the largest cities the gap can pass 10 degrees.
Tall buildings help cool city streets by letting breezes pass freely between them.
Show answer
False — Para B: tall buildings trap warm air in narrow streets and block cooling winds.
The 1995 Chicago heat wave killed more people than any other heat wave in United States history.
Show answer
Not Given — Para C notes more than 700 deaths in one week but never ranks it against other heat waves.
New York City's cool-roof program has been coating rooftops since 2009.
Show answer
True — Para D: a New York City program has coated millions of square feet of rooftops since 2009.
Matching Headings
The passage has 5 paragraphs, A–E.
Choose the best heading for each paragraph from the list below. There are two extra headings you will not use.
Where the extra heat comes from
How rising heat affects farmland
Measuring heat to guide action
Defining and discovering the heat island
Cooling cities with roofs and trees
The global spread of air conditioning
The human and energy toll of city heat
Show answer
iv. Defining and discovering the heat island — Para A defines the urban heat island and recounts Luke Howard's early observations of it.
Show answer
i. Where the extra heat comes from — Para B lists the sources of a city's extra heat: dark surfaces, waste heat, and few plants.
Show answer
vii. The human and energy toll of city heat — Para C covers the effects on human health and on energy demand.
Show answer
v. Cooling cities with roofs and trees — Para D presents two remedies: reflective cool roofs and street trees.
Show answer
iii. Measuring heat to guide action — Para E describes mapping heat block by block to decide where to act first.
Summary Completion
Complete the summary below. Choose no more than two words
from the passage for each answer.
Cities grow hotter than the land around them for several reasons. Dark road surfaces 1 most of the sunlight that hits them, engines and machines release their own 2 heat, and the loss of plants removes natural cooling. Two practical answers have emerged: pale, 3 roofs that bounce sunlight back to the sky, and street 4 that cool the air through shade and moisture.
Show answers
soak up — Para B: dark surfaces soak up most of the sunlight that strikes them.
waste — Para B: cities make their own waste heat from engines, air conditioners, and factories.
reflective — Para D: a roof coated with white or reflective paint sends most sunlight back toward the sky.
trees — Para D: street trees lower air temperatures through shade and moisture.
