Figure 4 ̈ In 1996, the federal gov-
ernment established standards to
reduce emissions of VOC-producing
chemicals used in dry cleaning.
Industrial Air Pollution Ecofact
Many industries, as well as power plants that generate electricity, Air Pollution’s Impact on Birds
burn fuel to produce energy. They usually burn fossil fuels. Scientists in Finland have docu-
Burning fossil fuels releases sulfur dioxide and nitrogen oxides mented the effects of harmful
into the air. Power plants that produce electricity emit at least emissions from a copper smelter in
two-thirds of all sulfur dioxide and more than one-third of all Finland on two species of birds
nitrogen oxides that pollute the air. that live nearby. The two species
of birds respond differently to the
Some industries, such as the drying cleaning industry shown pollutants containing heavy metals
in Figure 4, also produce VOCs. VOCs are chemical compounds and acidic substances. One species
that form toxic fumes. Oil refineries, chemical manufacturing appears to suffer directly from the
plants, furniture refinishers, and automobile repair shops also toxic effects of the pollutants. The
contribute to the VOCs in the air. other species suffers because the
amount of insect food for its
Regulating Air Pollution From Industry The Clean Air Act nestlings has been reduced. When
requires many industries to use scrubbers or other pollution- heavy metal emissions from the
control devices. Scrubbers remove some of the more harmful smelter decreased, a rapid
substances that would otherwise pollute the air. A scrubber, as improvement in breeding success
shown in Figure 5, is a machine that moves gases through a spray and decrease in the heavy metal
of water that dissolves many pollutants. found in the bones of nestlings
was observed.
Electrostatic precipitators are machines used in cement factories
and coal-burning power plants to remove dust particles from smoke- Figure 5 ̈ Scrubbers work by spray-
stacks. In an electrostatic precipitator, gas containing dust particles ing gases with water, which removes
is blown through a charged chamber. An electrical charge is trans- many pollutants.
ferred to the dust particles, which causes them to stick to one
another and the sides of the chamber. The clean gas is released
from the chamber, and the concentrated dust particles can then be
collected and removed. Electrostatic precipitators remove 22 mil-
lion metric tons (20 million tons) of ash generated by coal-burning
power plants from the air each year in the United States.
■✓● Reading Check Name two pollution-control devices. State how they
help to limit the amount of pollutants in air.
Section 1 What Causes Air Pollution? 329
Figure 6 ̈ The diagram below Smog When air pollution hangs over urban areas and reduces visi-
shows how smog is formed. Large bility, it is called smog. As you can see in Figure 6, smog results from
cities with dry, sunny climates and chemical reactions that involve sunlight, air, automobile exhaust,
millions of automobiles often suffer and ozone. Pollutants released by vehicles and industries are the
from smog. main causes of smog.
Temperature Inversions The circulation of air in the atmosphere
usually keeps air pollution from reaching dangerous levels. During
the day, the sun heats the surface of the Earth and the air near the
Earth. The warm air rises through the cooler air above and carries
pollutants away from the ground and into the atmosphere.
Sometimes, however, pollution is trapped near the Earth’s sur-
face. Usually, air temperatures decrease with altitude, but some-
times a temperature inversion occurs when the air above is
warmer than the air below. Figure 7 shows how a temperature
inversion traps pollutants near the Earth’s surface. The warmer air
above keeps the cooler air at the surface from moving upward. So,
pollutants are trapped below with the cooler air. If a city is
located in a valley, the city has a greater chance of experiencing
temperature inversions. Los Angeles, which is surrounded on three
sides by mountains, often has temperature inversions that trap
smog in the city.
Normal situation Temperature inversion
Solar Escaping Solar Trapped
radiation pollutants radiation pollutants
Cooler air Cool air
Figure 7 ̈ Normal air circulation Cool air
is shown at left, whereas a tempera-
ture inversion, in which pollutants Warm air Warm inversion
are trapped near the Earth’s surface, layer
is shown at right.
Cool air
S E C T I O N 1 Review
1. Name five primary air pollutants, and give important CRITICAL THINKING
sources for each.
5. Making Decisions Read the passage on the
2. Name the two major sources of air pollution in California Zero-Emission Vehicle Program. Should
urban areas. automobile makers be made to adhere to quotas of
zero-emission vehicles set by states, even if the quota
3. Describe the way in which smog forms. causes automakers to lose revenue? READING SKILLS
4. Define the term temperature inversion. Explain how 6. Analyzing Relationships Can you think of any
temperature inversion traps pollutants near Earth’s other possible type of pollution-control device that
surface. could be used to remove particulates from smokestacks
in a manner similar to an electrostatic precipitator?
330 Chapter 12 Air
SECTION 2
Air, Noise, and Light Pollution
EARTH SCIENCE CONNECTION
People who are very young or very old and people who have Objectives
heart or lung problems are most affected by air pollutants.
Decades of research have linked air pollution to disease. But ̈ Describe three short-term effects
because pollution adds to the effects of existing diseases, no death and three long-term effects of air
certificates list the cause of death as air pollution. Instead, dis- pollution on human health.
eases such as emphysema, heart disease, and lung cancer are cited
as causes of death. The American Lung Association has estimated ̈ Explain what causes indoor air pol-
that Americans pay tens of billions of dollars a year in health lution and how it can be prevented.
costs to treat respiratory diseases caused by air pollution.
̈ Describe three human health prob-
Short-Term Effects of Air Pollution on Health lems caused by noise pollution.
Many of the effects of air pollution on people’s health are short- ̈ Describe solutions to energy waste
term and are reversible if their exposure to air pollution decreases. caused by light pollution.
The short-term effects of air pollution on people’s health include
headache; nausea; irritation to the eyes, nose, and throat; tightness Key Terms
in the chest; coughing; and upper respiratory infections, such as
bronchitis and pneumonia. Pollution can also make the condition sick-building syndrome
of individuals who suffer from asthma and emphysema worse. asbestos
decibel (dB)
Long-Term Health Effects of Air Pollution
Long-term effects on health that have been linked to air pollution
include emphysema, lung cancer, and heart disease. Long-term
exposure to air pollution may worsen medical conditions suffered
by older people and may damage the lungs of children.
www.scilinks.org
Topic: Respiratory
Disorders
Code: HE81306
Figure 8 ̈ This police officer wears
a smog mask as he directs traffic in
Bangkok, Thailand.
Section 2 Air, Noise, and Light Pollution 331
Connection to Chemistry Indoor Air Pollution
Formaldehyde Formaldehyde is The quality of air inside a home or a building is sometimes worse
a colorless gas that has a strong than the quality of the air outside. Chemicals that are used to
odor. It is a very common indus- make carpets, building materials, paints, and furniture are major
trial and commercial chemical sources of pollutants in buildings. Figure 9 shows examples of
that is used to make building some indoor air pollutants.
materials and household prod-
ucts. In the home, significant Buildings that have very poor air quality have a condition
amounts of formaldehyde are called sick-building syndrome. Sick-building syndrome is most
found in adhesives in plywood, common in hot places where buildings are tightly sealed to keep
particle board, furniture, and car- out the heat. In Florida, for example, a new, tightly sealed county
pet. Other sources of formalde- courthouse had to be abandoned. Half of the people who worked
hyde may be foam insulation, gas there developed allergic reactions to fungi that were growing in
stoves, tobacco smoke, and dry- the air-conditioning ducts, ceiling tiles, carpets, and furniture.
cleaned clothing. The health
effects of formaldehyde may Identifying and removing the sources of indoor air pollution
include eye irritation, burning is the most effective way to maintain good indoor air quality.
sensations in the throat, nausea, Ventilation, or mixing outdoor air with indoor air, is also neces-
and difficulty breathing. sary for good air quality. Activities such as renovation and paint-
ing, which cause indoor air pollution, require good ventilation.
■✓● Reading Check Why is sick-building syndrome most common in
hot places?
The Health Effects of Ground-Level Ozone
You have learned that the ozone ̈ Children who engage in vigorous have other damaging effects on
layer in the stratosphere shields the outdoor activities where pollutant human health. Lung diseases such
Earth from the harmful effects of concentrations are often high may as bronchitis and emphysema may
ultraviolet radiation from the sun. have a greater risk of developing be aggravated by ozone. Scientists
At the surface of the Earth, how- asthma or other respiratory illnesses.
ever, ozone is a human-made air
pollutant that at certain concentra- producing chemicals may be trans-
tions damages human health. ported hundreds of kilometers from
their source.
Ozone forms from the reaction of
volatile organic compounds (VOCs) As ozone concentrations in the
and nitrogen oxides (NOx) in the atmosphere increase, greater num-
presence of heat and sunlight. High bers of people may experience
concentrations of ozone form in the harmful health effects of ozone on
atmosphere on sunny days that have the lungs. Some of the short-term
high temperatures. The sources of effects of ozone on health include
VOCs and NOx emissions are largely irritation of the respiratory system,
motor vehicles, power plants, gaso- a reduction in lung function, the
line vapors, and chemical solvents. aggravation of asthma, and inflam-
Most ozone pollution forms in urban mation to the lining of the lungs.
and suburban areas. However, ozone- Scientists believe that ozone may
332 Chapter 12 Air
Figure 9 ̈ Some
indoor air pollutants
and their sources are
shown here.
EARTH SCIENCE CONNECTION
Those who are most at risk
from ozone include children, adults
who exercise or work outdoors,
older people, and people who suffer
from respiratory diseases. In addi-
tion, there are some healthy individ-
uals who have unusually high
susceptibility to ozone.
̈ A therapist performs a lung-function test on a patient by using CRITICAL THINKING
a machine that measures various aspects of lung function.
1. Making Decisions Write a brief
believe that permanent lung injury may have reduced lung function as paragraph explaining whether or
may result from repeated short- adults. Exposure to ozone may also not lung-function tests should be
term exposure to ozone pollution. accelerate the natural decline in mandatory for children who live in
Children who are regularly exposed lung function that is part of the urban areas where high concentra-
to high concentrations of ozone aging process. tions of ozone are frequent.
WRITING SKILLS
2. Making Decisions If lung-
function tests become mandatory,
who will pay for these tests, and who
will provide the equipment? Would
these tests be performed at school,
in a doctor’s office, or at a hospital?
Section 2 Air, Noise, and Light Pollution 333
Figure 10 ̈ Radon Gas Radon is a colorless, tasteless, odorless gas. It is also
Asbestos (right) forms radioactive. Radon is one of the elements produced by the decay
in long, thin fibers. The of uranium, a radioactive element that occurs naturally in the
worker above is removing Earth’s crust. Radon can seep through cracks and holes in foun-
debris from a structure that was dations into homes, offices, and schools, where it adheres to dust
built with asbestos. particles. When people inhale the dust, radon enters their lungs.
In the lungs, radon can destroy the genetic material in cells that
Table 2 ̄ line the air passages. Such damage can lead to cancer, especially
among people who smoke. Radon is the second-leading cause of
Intensity of lung cancer in the United States.
Common Noises
Asbestos Several minerals that form in long, thin fibers and
Noise Intensity (dB) that are valued for their strength and resistance to heat are
Rocket engine 180 called asbestos. Asbestos is primarily used as an insula-
Jet engine 140 tor and as a fire retardant, and it was used exten-
Rock concert 120 sively in building materials. The U.S.
Car horn 110 government banned the use of most asbestos
Chainsaw 100 products in the early 1970s. Exposure to
Portable CD player 90–120 asbestos in the air is dangerous. Asbestos
Lawnmower fibers that are inhaled can cut and scar the
Conversation 90 lungs, which causes the disease asbestosis.
Whisper 60 Victims of the disease have more and more
Faintest sound 30 difficulty breathing and may eventually die
heard by the of heart failure. Schools in the United States
human ear 0 have taken this threat seriously. Billions of dol-
lars have been spent to remove asbestos from school
buildings. Figure 10 shows asbestos fibers and asbestos
removal from a building.
Noise Pollution
Unwanted sound is noise pollution, and it is one of the prices we
pay for modern living. It is irritating, and it damages our hearing
by destroying cells in our ears. Hearing loss has doubled in the
United States in the last 30 years. About 12 percent of teens have
permanent hearing loss, likely due to the prevalence of portable
listening devices. One study found that people living in a quiet
environment in Africa had better hearing at the age of 80 than
most Americans do at 30.
The intensity of sound is measured in units called decibels
(dB). Table 2 shows the intensity of some common noises. For
each 10-fold increase in decibel intensity, the decibel level is 10
times higher than the previous level. For example, 20 dB is 10
times the intensity of 10 dB. A sound of 120 dB is at the threshold
of pain. Noise pollution can be controlled by devices such as muf-
flers on vehicles and lawn mowers, and by insulation. In Europe,
MP3 players must produce no more than 100 dB of noise.
According to the National Institutes of Health, the safe threshold
for personal listening devices is 85 dB for 8 hours. Personal listen-
ing devices are not regulated in the United States.
334 Chapter 12 Air
Light Pollution Figure 11 ̈ This view of Seattle
shows how lighting in urban areas
Unlike air or water pollution, light pollution does not present a can cause skyglow, which is an effect
direct hazard to human health. However, light pollution does nega- of light that can dramatically reduce
tively affect our environment. Light pollution in urban areas dimin- our view of the night sky.
ishes our view of the night sky, as shown in Figure 11.
FIELD ACTIVITY
A more important environmental concern of lighting is energy
waste. For example, energy is wasted when light is directed upward Light Pollution At night, in
into the night sky and lost to space. Examples of light pollution are your neighborhood or from your
billboards and other signs that are lit from below, the lighting of front porch, note any efficient or
building exteriors, and poor-quality street lights. One solution to inefficient uses of light that you
energy waste includes shielding light so it is directed downward. see, and write down your obser-
Using time controls so that light is used only when needed and vations in your EcoLog.
using low-pressure sodium sources—the most energy-efficient
source of light—where possible are two other solutions.
■✓● Reading Check What are three sources of light pollution in a city?
S E C T I O N 2 Review
1. Describe the long-term effects and the short-term CRITICAL THINKING
effects of air pollution on health. 5. Making Comparisons Read the descriptions of
2. Describe two ways in which indoor air pollution can noise and light pollution in this section. Explain ways
be prevented. in which noise pollution and light pollution are similar
and ways they are different. READING SKILLS
3. Describe some of the human health problems
caused by noise pollution. 6. Analyzing Relationships Molds can grow in new,
tightly sealed buildings where the humidity is high and
4. Describe several solutions to the energy waste asso- the ventilation is poor. Explain how you would control
ciated with light pollution. the growth of mold in this type of environment.
Section 2 Air, Noise, and Light Pollution 335
SECTION 3
Acid Precipitation
EARTH SCIENCE CONNECTION
Objectives Imagine that you are hiking through the forests of the Adirondack
Mountains in New York. You come to a lake and sit down to rest.
̈ Explain the causes of acid precipi- You are amazed at how clear the water is; it is so clear that you
tation. can see the bottom of the lake. But after a few minutes you feel
uneasy. Something is wrong. What is it? Suddenly, you realize that
̈ Explain how acid precipitation the lake has no fish.
affects plants, soils, and aquatic
ecosystems. What Causes Acid Precipitation?
̈ Describe three ways that acid pre- This lake and thousands of lakes throughout the world are vic-
cipitation affects humans. tims of acid precipitation, which is also known as acid rain.
Acid precipitation is precipitation such as rain, sleet, or snow
̈ Describe ways that countries are that contains a high concentration of acids. When fossil fuels
working together to solve the are burned, they release oxides of sulfur and nitrogen. When
problem of acid precipitation. the oxides combine with water in the atmosphere, they form
sulfuric acid and nitric acid, which fall as acid precipitation.
Key Terms This acidic water flows over and through the ground, and into
lakes, rivers, and streams. Acid precipitation can kill living
acid precipitation things, and can result in the decline or loss of some local ani-
pH mal and plant populations.
acid shock
A pH (power of hydrogen) number is a measure of how acidic
or basic a substance is. A pH scale is shown in Figure 12. As you
can see from the scale, the lower the pH number is, the more
acidic a substance is; the higher a pH number is, the more basic
a substance is. Each whole number on the pH scale indicates a
tenfold change in acidity.
Figure 12 ̈ The pH scale measures Human saliva
how basic or how acidic a substance Tap water
is. Below are the pH measurements
of some common substances.
Acid rain Acid rain
(extreme) (average) Rain
3.5 4.0 5.0 6.0
Carbonated
Lemon soft Tomato Human Sea Household
juice Milk blood water ammonia
juice Vinegar drink Detergents
1 2 3 4 5 6 7 8 9 10 11 12
Increasing acidity Increasing basicity
336 Chapter 12 Air
Pure water has a pH of 7.0. Normal precipitation is slightly Atmospheric gases
acidic, because atmospheric carbon dioxide dissolves into the pre- and H2O
cipitation and forms carbonic acid. Normal precipitation has a
pH of about 5.6. Acid precipitation has a pH of less than 5.0. combine with combine with
Figure 13 shows how acid precipitation forms. SO2 NO2
The pH of precipitation varies between different geographic Sulfuric acid Nitric acid
areas. For example, Eastern Europe and parts of Scandinavia have H2SO4 HNO3
precipitation with a pH of 4.3 to 4.5, whereas the remainder of
Europe has precipitation with pH values of 4.5 to 5.1. The pH of Acid precipitation
precipitation in the eastern United States and Canada ranges from
4.2 to 4.8. The most acidic precipitation in North America occurs Figure 13 ̈ Sulfur oxides and nitro-
around Lake Erie and Lake Ontario. It has a pH of 4.2. gen oxides combine with water in the
atmosphere to form sulfuric and nitric
How Acid Precipitation Affects Soils and Plants acids. Rainfall that contains these
acids is called acid precipitation.
Acid precipitation can cause a drop in the pH of soil and water.
This increase in the concentration of acid is called acidification.
Acidification changes the balance of a soil’s chemistry in several
ways. When the acidity of soil increases, some nutrients are dis-
solved and washed away by rainwater. Increased acidity causes
aluminum and other toxic metals to be released and possibly
absorbed by the roots of plants. Aluminum also causes root dam-
age. Sulfur dioxide dissolved in water vapor clogs the openings on
the surfaces of plants. Figure 14 shows the harmful effects of acid
precipitation on trees.
■✓● Reading Check How does the pH of pure water compare with that
of acid precipitation?
Chain-of-
Events Chart
Create the Graphic Organizer
entitled “Chain-of-Events Chart”
described in the Appen-
dix. Then, fill in the chart
with details about each
step of the formation of
acid precipitation.
Figure 14 ̈ The trees in this forest
in Poland show the dramatic effect
that acid precipitation can have on
plants.
Section 3 Acid Precipitation 337
Figure 15 ̈ Acid shock can cause Acid Precipitation and Aquatic Ecosystems
the death of many fish.
Aquatic animals are adapted to live in an environment with a
QuickLAB particular pH range. If acid precipitation falls on a lake and
changes the water’s pH, acid can kill fish and other aquatic ani-
Neutralizing Acid mals. The change in pH is not the only thing that kills fish. Acid
Precipitation precipitation causes aluminum to leach out of the soil surround-
ing a lake. The aluminum accumulates in the gills of fish and
Procedure interferes with oxygen and salt exchange. As a result, fish are
1. Pour 1/2 Tbsp of vinegar into slowly suffocated.
one cup of distilled water, The effects of acid precipitation are worst in the spring, when
and stir the mixture well. acidic snow that accumulated in the winter melts and rushes into
Check the pH of the mixture lakes and other bodies of water. This sudden influx of acidic water
by using pH paper. The pH that causes a rapid change in the water’s pH is called acid shock.
should be about 4. This phenomenon may kill large numbers of fish, as shown in
2. Crush one stick of blackboard Figure 15. Acid shock also affects the reproduction of fish and
chalk into a powder. Pour the amphibians. They produce fewer eggs, and these eggs often do not
powder into the vinegar and hatch. The offspring that do survive often have birth defects and
water mixture. Check the pH of cannot reproduce.
the mixture.
Acid Precipitation and Humans
Analysis
1. Did the vinegar and water mix- Acid precipitation can affect humans in a variety of ways. Toxic
metals such as aluminum and mercury can be released into the
ture become more or less acidic environment when soil acidity increases. These toxic metals can
after the powdered chalk was find their way into crops, water, and fish. The toxins then poison
poured in? the human body.
338 Chapter 12 Air Acid precipitation can lead to other human health prob-
lems. Research has indicated that there may be a correlation
between large amounts of acid precipitation received by a com-
munity and an increase in respiratory problems in the commu-
nity’s children.
The standard of living of some people is affected by acid pre-
cipitation. Decreases in numbers of fish caused by the acidification
of lakes and streams can influence the livelihood of commercial
fishers and people involved in the sport-fishing industry. Forestry
is also affected when trees are damaged by acid precipitation.
Acid precipitation can dissolve the calcium carbonate in
common building materials, such as concrete, marble, and lime-
stone. Some of the world’s most important monuments are
being dissolved by acid precipitation. These monuments include
the Acropolis in Greece, the Taj Mahal in India, ancient tem-
ples and pyramids in Egypt and in the rain forests of Central
America, and the Lincoln Memorial in Washington, DC.
International Conflict and Cooperation
One problem in controlling acid precipitation is that pollutants
may be released in one area and fall to the ground hundreds of
kilometers away. For example, almost half of the acid precipita-
tion that falls in southeastern Canada results from pollution pro-
duced in the northeastern United States. Figure 16 shows areas of
the world that produce pollutants and areas which are then Figure 16 ̈ Acid precipitation is a
affected by acid precipitation. Acid precipitation is an interna- global problem.
tional problem. In the spirit of cooperation, Canada and the
United States signed the Canada–U.S. Air Quality Agreement in www.scilinks.org
1991. Both countries agreed to reduce emissions that flow across
the Canada–U.S. boundary. Topic: Acid Rain
Code: HE80008
As a result of this agreement, sulfur dioxide emissions in the
United States and Canada have been reduced dramatically since the
1970s. In Europe, similar agreements have reduced sulfur dioxide
emissions by about 40 percent since 1980, although reductions in
emissions of nitrogen oxides have been offset by vehicle exhaust
from increased road traffic. Meanwhile, China still burns large
amounts of high-sulfur coal without pollution controls. The pol-
luted air that results produces acid precipitation in other parts of
Asia that are far from the coal-burning plants in China.
■✓● Reading Check How can pollutants from the United States cause
acid precipitation in Canada?
S E C T I O N 3 Review
1. Explain how acid precipitation forms. CRITICAL THINKING
5. Inferring Relationships In addition to negatively
2. Describe the harmful effects that acid precipitation
can have on plants, soils, and aquatic ecosystems. affecting forestry and the fishing industry, how
might acid precipitation affect local economies?
3. Describe three ways in which acid precipitation can
affect humans. 6. Analyzing Viewpoints Write a short essay in
which you discuss whether or not a country that
4. Describe a way in which countries are working releases significant amounts of pollutants into the air
together to solve the problem of acid precipitation. that fall as acid precipitation in another country
should be expected to pay some of the costs of
cleanup. WRITING SKILLS
Section 3 Acid Precipitation 339
12C H A P T E R Highlights
1 What Causes Air Pollution? Key Terms Main Ideas
air pollution, 325 ̈ Primary pollutants are pollutants put directly
primary pollutant, in the air by human activity.
325 ̈ Secondary pollutants are formed when a pri-
secondary pollutant, mary pollutant comes into contact with other
primary pollutants or with naturally occurring
325 substances and a chemical reaction takes place.
smog, 330
temperature ̈ Most air pollution comes from vehicles and
industry.
inversion, 330
̈ Air pollution that hangs over cities and
reduces visibility is called smog.
̈ Pollution can be trapped near the surface of
the Earth by a temperature inversion.
2 Air, Noise, and Light Pollution sick-building ̈ Air pollution may have both long- and short-
syndrome, 332 term effects on human health.
asbestos, 334 ̈ The air indoors may be more polluted than
the air outside. Plastics, cleaning chemicals,
decibel (dB), 334 and building materials are major sources of
indoor air pollution.
̈ Noise is a pollutant that affects human
health and the quality of life.
̈ Inefficient lighting diminishes our view of the
night sky and wastes energy.
3 Acid Precipitation acid precipitation, ̈ Acid precipitation is precipitation such as
336 rain, sleet, or snow that contains a high con-
340 Chapter 12 Highlights centration of acids.
pH, 336
̈ Acid shock occurs when a sudden influx of
acid shock, 338 acidic water enters a lake or stream and causes
a rapid change in pH that harms aquatic life.
̈ Pollutants released in one geographical area
may fall to the ground hundreds of kilometers
away as acid precipitation—sometimes in
another country.
12C H A P T E R Review
Using Key Terms 13. Which of the following substances is not
involved in the chemical reaction that pro-
Use each of the following terms in a sentence. duces smog?
a. sunlight
1. air pollution b. particulate matter
c. automotive exhaust
2. smog d. ozone
3. temperature inversion 14. Which of the following respiratory diseases
is considered a long-term effect of air pollu-
4. sick-building syndrome tion on human health?
a. emphysema
5. pH b. bronchitis
c. pneumonia
For each pair of terms, explain how the meanings d. all of the above
of the terms differ.
15. Which of the following substances is a color-
6. primary pollutant and secondary pollutant less, tasteless, and odorless radioactive gas?
a. asbestos
7. asbestos and radon b. carbon monoxide
c. radon
8. pH and acid precipitation d. ozone
9. acidification and acid shock 16. A sound measuring 40 dB has how many
times the intensity of a sound that measures
STUDY TIP 10 dB?
a. 4 times
Predicting Exam Questions Before you take a b. 30 times
test, do you ever attempt to predict what the ques- c. 400 times
tions will be? For example, of the 10 multiple-choice d. 1,000 times
questions that appear on this page, how many would
you have predicted to be asked in a review of this 17. Which of the following choices is not an
chapter? Before your next test, predict and answer effective solution to the energy waste related
possible exam questions. to inefficient lighting?
a. using low-pressure sodium lighting sources
Understanding Key Ideas b. pointing lights on billboards and street
signs upward
10. Which of the following air pollutants is not c. placing light sources on time controls
a primary pollutant? d. shielding light to direct it downward
a. particulate matter
b. ozone 18. Which of the following numbers on the pH
c. sulfur dioxide scale would indicate that a substance is
d. volatile organic compounds acidic?
a. 5.0
11. A device used to clean exhaust gases before b. 7.0
they exit an automobile’s tailpipe is called a(n) c. 9.0
a. electrostatic precipitator. d. none of the above
b. catalytic converter.
c. scrubber. 19. Normal precipitation has a pH of
d. None of the above a. 7.0.
b. 5.6.
12. The majority of sulfur dioxide produced by c. 5.1.
industry comes from d. 4.5.
a. oil refineries.
b. dry cleaners.
c. chemical plants.
d. coal-burning power plants.
Chapter 12 Review 341
12C H A P T E R Review
Short Answer Concept Mapping ?
??
20. Define the term zero-emission vehicle. What
types of vehicles qualify as zero-emission 27. Use the following terms to create a concept
vehicles? map: air pollution, primary pollutant, volatile
organic compound, scrubber, secondary pol-
21. Identify five indoor air pollutants and exam- lutant, smog, and temperature inversion.
ples of sources of each pollutant.
Critical Thinking
22. Explain the health hazards that radon gas
poses for humans. 28. Making Decisions Five states now have zero-
emission vehicle programs in place that will
23. Why does acid precipitation damage monu- help decrease some primary pollutants. What
ments such as the Acropolis, the Taj Mahal, would be the advantages or disadvantages of
and the Lincoln Memorial? a federal program that required automobile
makers to produce a set number of ZEVs
24. Explain why acid precipitation is a source of nationwide?
international conflict and why international
cooperation is necessary to resolve the 29. Making Decisions In some cities, noise-pollu-
problem. tion laws, such as restrictions placed on the
use of leaf blowers, have been put in place.
Interpreting Graphics Do you think the benefits of noise reduction
outweigh the costs of enforcing the law?
The map below shows the pH of precipitation
that has been measured at field stations in the 30. Inferring Relationships As you read under
northeastern United States. Use the map and the head “International Conflict and
legend to answer questions 25–26. Cooperation,” about half of the acid precipi-
tation that falls in southeastern Canada is pro-
25. Which area(s) of the northeastern United duced by pollutants from the United States.
States have the most-acid precipitation? How do the acid pollutants get from their
sources to southeastern Canada? READING SKILLS
26. Are the areas that have the highest pH
located close to or far from major cities?
Cross-Disciplinary Connection
31. Health Asbestos, lead paint, tobacco, and
many other products have been linked to
adverse effects on human health. Research
one such case that has been brought into the
courts. Describe the allegations and the out-
come of the trial and write a paragraph that
explains whether you agree or disagree with
the decision. WRITING SKILLS
Portfolio Project
32. Make a Poster Create a poster similar to the
diagram that appears in Figure 9. This dia-
gram may be of your home, your garage, a
portion of your school, or a particular class-
room in your school. Use the diagram to
identify and label potential sources of indoor
air pollutants. Photographs may be used to
document these sources.
342 Chapter 12 Review
MATH SKILLS READING SKILLS
Use the graph below to answer questions 33 Read the passage below, and then answer
and 34. the questions that follow.
33. Analyzing Data The graph below shows the Lichens are unique organisms that consist of a
change in air-pollution emissions in the fungus and microscopic alga that live together
United States between 1970 and 1997. and function as a single organism. The alga is
Excluding NOx, which emissions category the photosynthetic partner, whereas the fungus
experienced the greatest decrease over this absorbs water and minerals and anchors the
period of time? plant. Lichens form crusts or leafy growths on
rocks, trees, and bare ground. Lichens do not
34. Interpreting Graphics Why is lead, Pb, shown have roots. Instead, they absorb the nutrients
separately from the other air pollutants? they need directly from rain. Lichens grow
very slowly and can live for centuries. Species
150 250 of lichens have adapted to almost every envi-
ronment in the world.
Emissions 1970
(in millions of tons) Lichens are sensitive to air pollution, par-
120 1997 200 ticularly sulfur dioxide. When lichens are
Emissions exposed to high levels of sulfur dioxide, the
(in thousands of tons) sulfur destroys chlorophyll and inhibits photo-
90 150 synthesis. So, lichens are good indicators of air
pollution. Lichens usually disappear from areas
60 100 where sulfur dioxide levels are high. Where the
air is free of pollutants, a greater number of
30 50 lichens will usually be present. In areas where
sulfur dioxide pollution is decreasing, lichens
0 0 will slowly return and colonize the area.
CO NOX VOC PM-10 SO2 Pb
1. Which of the following statements about
Air Pollutants lichens is true?
a. Lichens are present when sulfur diox-
WRITING SKILLS ide levels are high.
b. Lichens absorb nutrients through their
35. Outlining Topics Outline the major sources root systems.
of air pollution in the United States. Include c. Lichens photosynthesize.
information about pollution sources and d. Lichens grow only where the climate is
pollution types. moderate.
36. Writing Persuasively Write a letter to a leg- 2. Where would you be most likely to see
islator that expresses your concern about a the greatest number of lichens?
particular aspect of air, noise, or light pollu- a. in areas where sulfur dioxide levels are
tion that is important to you. high
b. in areas where sulfur dioxide levels
are low
c. in areas where sulfur dioxide levels are
decreasing
d. in areas where sulfur dioxide is absent
Chapter 12 Review 343
12C H A P T E R Standardized Test Prep
Understanding Concepts Reading Skills
Directions (1–4): For each question, write on a Directions (7–8): Read the passage below. Then
separate sheet of paper the letter of the correct answer the questions.
answer.
Power plants that generate our nation’s
1 What is the biggest cause of air pollution? electricity must burn fuel to get the energy they
need. They usually burn fossil fuels, but fossil
A. dust particles fuels release huge quantities of sulfur dioxide
B. forest fires and nitrogen oxide into the air. The Clean Air
C. human activities Act requires many industries to use pollution-
D. volcanic eruptions control devices, such as scrubbers.
2 Which of the following releases the most Scrubbers remove some of the more harmful
substances that would otherwise pollute the
primary pollutants into the air? air. A scrubber is a machine that moves gases
F. electric power plants through a spray of water which dissolves
G. manufacturing plants many pollutants. In electrostatic precipitators,
H. mining operations gas containing dust particles is blown through
I. transportation industry a charged chamber. An electrical charge is
transferred to the dust particles, which causes
3 Which of the following is a long-term them to stick to one another and the sides of
the chamber. The clean gas is released from the
health effect of air pollution? chamber, and the concentrated dust particles
A. blindness can then be collected and removed.
B. diabetes
C. emphysema 7 Where would you most likely find an
D. hepatitis
electrostatic precipitator being used?
4 Which of the following statements is true? A. car factory
B. bakery
F. Ground-level ozone is harmless to C. gas station
children. D. power plant
G. Noise pollution occurs at low decibel 8 How do pollution-control devices affect
levels.
acid precipitation?
H. Light pollution is a direct hazard to
human health. Directions (9): Read the passage below. Then
answer the question.
I. Sick-building syndrome is caused by poor
air quality. The Environmental Protection Agency set
up an allowance trading system designed to
Directions (5–6): For each question, write a short reduce sulfur-dioxide emissions. In this system,
response. one ton of sulfur dioxide emission is equiva-
lent to one allowance. Sulfur dioxide
5 Plant communities have adapted over long allowances are inexpensive and can be bought
from the EPA. There are a limited number of
periods of time to the acidity of the soil in allowances allocated each year.
which they grow. Acid precipitation can
cause a drop in the pH of soil. Analyze the 9 How does a company use the allowance
changes to soil that are caused by
acidification. trading system to comply with the Clean
Air Act?
6 Clean air consists mostly of nitrogen and
oxygen gas, as well as very small amounts
of argon, carbon dioxide, and water vapor.
Substances that pollute the air can be in the
form of solids, liquids, or gases.
Differentiate between primary and
secondary air pollutants.
344 Chapter 12 Standardized Test Prep
Interpreting Graphics
Directions (10–13): For each question below, record the correct answer on
a separate sheet of paper.
The illustration below shows the formation of acid precipitation in the
atmosphere. Use it to answer questions 10 through 12.
Formation of Acid Precipitation
Atmospheric gases
and H2O
combine with combine with
SO2 NO2
Sulfuric acid Nitric acid
H2SO4 HNO3
Acid precipitation
0 What is the relationship between sulfur dioxide (SO2) and sulfuric
acid (H2SO4)?
F. Sulfur dioxide combines with oxygen to form nitric acid.
G. Sulfur dioxide is the main pollutant that forms nitric acid.
H. Sulfur dioxide is the main pollutant that forms sulfuric acid.
I. Sulfur dioxide combines with nitrogen dioxide to form ozone.
q What are the two main polluting components in acid precipitation?
A. ozone and oxygen atoms C. sulfuric acid and nitric acid
B. ozone and water D. sulfuric acid and water
w What is the relationship between nitrogen dioxide (NO2) and nitric Test
acid (HNO3)? For questions involv-
F. Nitrogen dioxide combines with ozone to form oxygen. ing chemical reac-
G. Nitrogen dioxide is the main pollutant that forms nitric acid. tions, write out the
H. Nitrogen dioxide combines with oxygen to form ozone. chemical formulas to
I. There is no relationship between nitrogen dioxide and nitric acid. better visualize the
entire reaction.
e What is the main cause of acid precipitation?
A. the ozone hole
B. oxygen atoms
C. sulfur atoms
D. nitrogen dioxide and sulfur dioxide
Chapter 12 Standardized Test Prep 345
12C H A P T E R Exploration Lab: MODELING
Objectives The Acid Test
̈ Perform a chemical reaction that Acid precipitation is one of the effects of air pollution. When
produces sulfur dioxide, a compo- pollutants that contain nitrogen or sulfur react with water vapor
nent of acid precipitation. in clouds, dilute acid forms. These acids fall to Earth as acid
precipitation.
̈ USING SCIENTIFIC METHODS
Often, acid precipitation does not occur in the same place
Hypothesize what the effects of where the pollutants are released. The acid precipitation usu-
acids that contain sulfur on plants ally falls some distance downwind—sometimes hundreds of
will be. kilometers away. Thus, the sites where pollutants that cause
acid precipitation are released may not suffer the effects of acid
Materials precipitation.
beaker, 50 mL Coal-burning power plants are one source of air pollution.
clear plastic bags, large (2) These power plants release sulfur dioxide into the air. Sulfur
houseplants of the same type, dioxide reacts with the water vapor in air to produce acid that
contains sulfur. This acid later falls to Earth as acid precipitation.
potted (2)
sodium nitrite (2 g) In this investigation, you will create a chemical reaction that
sulfuric acid, 1 M (2 mL) produces sulfur dioxide. The same acids that result from coal-
twist tie or tape burning power plants will form. You will see the effects of acid
precipitation on living things—in this case, plants.
̈ Step 1 Place a plant and a beaker
that contains sodium nitrite into a Procedure
plastic bag. Do not seal the bag.
1. Place 2 g of sodium nitrite in a
beaker. Place a plant and the
beaker inside a plastic bag. Do
not seal the bag.
CAUTION: Steps 2–4 should be
carried out only under a fume
hood or outdoors.
2. Carefully add 2 mL of a 1 M
solution of sulfuric acid to the
beaker. Immediately seal the
bag tightly, and secure the bag
with a twist tie or tape. CAU-
TION: Because this reaction
produces sulfur dioxide, a toxic
gas, the bag should have no
leaks. If a leak occurs, move
away from the bag until the
reaction is complete and the gas
has dissipated.
3. Seal the same type of plant in
an identical bag that does not
contain sodium nitrite or sulfu-
ric acid.
346 Chapter 12 Exploration Lab
Day Control Plant Experimental Plant
1 DO NOT WRITE IN THIS BOOK
2
3
4. After 10 minutes, cut both bags open. Stay at least 5 m from
the bags as the sulfur dioxide gas dissipates. Keep the plants
and bags under the fume hood.
5. Predict the effects of the experiment on each plant over the
next few days. Record your predictions.
6. Observe both plants over the next three days. Record your
observations below.
Analysis
1. Examining Data How closely did your predictions about
the effects of the experiment on each plant match your
observations?
2. Explaining Events What does this experiment suggest about
the effects of acid precipitation on plants?
Conclusions
3. Drawing Conclusions In what ways is this a realistic model
of acid precipitation?
4. Drawing Conclusions In what ways is this experiment not a
realistic simulation of acid precipitation?
Extension
1. Analyzing Models Would you expect to see similar effects
occur as rapidly, more rapidly, or less rapidly in the
environment? Explain your answer.
2. Building Models Acid precipitation is damaging to plants
because it clogs the openings on the surfaces of plants and
interferes with photosynthesis. What kind of a safe model
would demonstrate the damaging effects of acid precipita-
tion on plant photosynthesis? Would this model be a realis-
tic simulation of acid precipitation?
Chapter 12 Exploration Lab 347
EARTH SCIENCE CONNECTION
LIGHT SOURCES
MAP SKILLS
This map of what the Earth looks like from space habitable than others. Examples of areas on our
at night shows light sources that are human in ori- planet that do not support large populations
gin. The map is a composite image made from include deserts, high mountains, polar regions, and
hundreds of images taken by orbiting satellites. tropical rain forests. From the map, can you identify
Use the map of light sources on Earth to answer regions of the Earth where climatic conditions may
the questions below. not be able to support large human populations?
What are some of these places?
1. Inferring Relationships Using the brightness of
the light sources on the map as a key, can you 3. Finding Locations Many large cities are seaports
estimate the locations of some of the most densely that are located along the coastlines of the world’s
populated areas on Earth? Where are some of oceans. From the map, can you pick out light
these areas? sources along coastlines that might indicate the sites
of large ports? Identify some of these cities by name.
2. Inferring Relationships Some climatic condi-
tions on Earth, such as extreme cold, heat, wetness, 4. Inferring Relationships From the differences in
or a thin atmosphere, make parts of our planet less the density of the light sources, can you pick out any
international borders?
348 Chapter 12 Maps in Action
EARTH SCIENCE CONNECTION
THE DONORA, PENNSYLVANIA, KILLER SMOG
For the residents of the small respiratory ailments be evacuated other people were at home in bed or
Monongahela Valley town of from town. In an attempt to allevi- were filling the corridors and exam-
Donora, Pennsylvania, living with ate the suffering of people who were ining rooms of the two area hospi-
the smoke that billowed from the struggling to breathe, several local tals. People who were less affected
local zinc smelter was an everyday firemen carried oxygen tanks by the smog suffered from nausea
occurrence—until October 26, through the streets to different and vomiting, headaches, and
1948. On that night, a temperature homes. Because of the low visibility, abdominal cramps. Some victims
inversion and an absence of wind the firemen had to feel their way were choking or coughing up blood.
began to trap a deadly mixture of along buildings and fences. Because The zinc smelter resumed operation
sulfur dioxide, carbon monoxide, the supply of oxygen was limited, on Monday morning, October 31.
and metal dust that would hang in only a few breaths of oxygen could
the valley air for five days. Over that be given to each person. Eleven peo- The Aftermath
period of time, 20 residents lost ple died that night. A makeshift
their lives and 7,000 other resi- morgue was set up in the local com- The smog of Donora was one of the
dents—about half of the town’s pop- munity center. United States’ most serious environ-
ulation—suffered some form of mental disasters. Shortly after the
respiratory problems. Even as the killer smog choked incident, investigations were under-
the valley, the zinc smelter continued taken by the Pennsylvania
The Weekend of the Killer Smog production throughout the night. Department of Health, the U.S.
The smelter continued sending more Public Health Service, and other
By Saturday afternoon, October 29, gases and dust into the air over agencies. This was the first time an
1948, the yellowish smog had Donora. The smelter was shut down organized attempt was made to
become so thick that spectators in only when the magnitude of the document the effects of air pollution
the stands at a local high-school problem became apparent—6:00 on health in the United States. The
football game could not see the A.M. on Sunday, October 30, 1948. knowledge that air pollution could
players on the field. Only the whis- be linked directly to the deaths of
tles of the referees could be heard. Later that day, a drizzling rain individuals resulted in legislation at
By nightfall, driving was unsafe. began to fall and washed the pollu- the local, regional, state, and federal
This proved to be catastrophic tants from the sky. By the time the levels. These laws were set to limit
because doctors recommended that rain fell, 20 people ages 52 to 85, emissions of sulfur dioxide, carbon
any residents who suffered from who suffered from respiratory ail- monoxide, particulate matter, and
ments, were dead. Thousands of other pollutants. The greatest legacy
of the Donora tragedy was passage
of the Clean Air Act of 1970.
What Do You Think?
Who do you think should be
held responsible for the
Donora, Pennsylvania, disas-
ter? Explain your answer.
Given what you know about
the regulation of industrial pol-
lutants under the Clean Air
Act, do you think another inci-
dent such as the Donora killer
smog could happen in the
United States today?
̈ This historical photo from the Pittsburgh Gazette captures the town of Donora,
Pennsylvania, as it is enveloped in smog at noon on Saturday, October 28, 1948.
Chapter 12 Society and the Environment 349
13Atmosphere and Climate Change CHAPTER
1 Climate and
Climate Change
2 The Ozone Shield
3 Global Warming
PRE-READING ACTIVITY
Tri-Fold
Before you
read this
chapter, cre-
ate the FoldNote entitled
“Tri-Fold” described in the
Reading and Study Skills sec-
tion of the Appendix. Write
what you know about cli-
mate change in the column
labeled “Know.” Then, write
what you want to know in
the column labeled “Want.”
As you read the chapter,
write what you learn about
climate
change in
the column
labeled
“Learn.”
The climate on Earth can be very
extreme. This satellite image of
Hurricane Fran was taken before it
struck the coastline of North Carolina
in early September 1996.
350 Chapter 13 Atmosphere and Climate Change
SECTION 1
Climate and Climate Change
EARTH SCIENCE CONNECTION
Weather is the state of the atmosphere at a particular place at a Objectives
particular moment. Climate is the long-term prevailing weather
conditions at a particular place based upon records taken. To ̈ Explain the difference between
understand the difference between weather and climate, consider weather and climate.
Seattle, Washington, and Phoenix, Arizona. These two cities may
have the same weather on a particular day. For example, it may be ̈ Identify four factors that deter-
raining, warm, or windy in both places. But their climates are mine climate.
quite different. Seattle’s climate is cool and moist, whereas
Phoenix’s climate is hot and dry. ̈ Explain why different parts of the
Earth have different climates.
What Factors Determine Climate?
̈ Explain what causes the seasons.
Climate is determined by a variety of factors. These factors
include latitude, atmospheric circulation patterns, oceanic circula- Key Terms
tion patterns, the local geography of an area, solar activity, and
volcanic activity. The most important of these factors is distance climate
from the equator. For example, the two locations shown in latitude
Figure 1 have different climates mostly because they are at dif- El Niño
ferent distances from the equator. La Niña
Figure 1 ̈ At left is Trunk Bay on
the island of St. John in the U.S.
Virgin Islands, which is located near
the equator. Below is a photograph
of the Antarctic Peninsula.
Section 1 351
Ecofact Latitude
Coral Reefs Corals need sunlight The distance from the equator measured in degrees north or
to grow. They require water that south of the equator is called latitude. The equator is located at
is clear, warm, and has a stable 0° latitude. The most northerly latitude is the North Pole, at 90°
temperature. Because of these north, whereas the most southerly latitude is the South Pole, at
requirements, coral reefs occur in 90° south.
shallow waters of tropical oceans
between the Tropic of Cancer Low Latitudes Latitude influences climate because the amount of
(23.5° north latitude) and the solar energy an area of Earth receives depends on its latitude.
Tropic of Capricorn (23.5° south More solar energy falls on areas that are near the equator than
latitude). Water between these on areas that are closer to the poles, as shown in Figure 2. The
latitudes has an annual average incoming solar energy is concentrated on a relatively small sur-
temperature of about 21°C, which face area at the equator.
corals need to survive.
In regions near the equator, night and day are both about
Figure 2 ̈ At the equator, sunlight 12 hours long throughout the year. In addition, temperatures are
hits the Earth vertically. The sunlight high year-round, and there are no summers or winters.
is concentrated on a smaller surface
area at the equator. Away from the High Latitudes In regions closer to the poles, the amount of
equator, sunlight hits the Earth at an energy arriving at the surface is reduced. In the northern and
oblique angle and spreads over a southern latitudes, sunlight hits the Earth at an oblique angle and
larger surface area. spreads over a larger surface area than it does at the equator.
Yearly average temperatures near the poles are therefore lower
than they are at the equator. The hours of daylight also vary. At
45° north and south latitude, there is as much as 16 hours of
daylight each day in summer and as little as 8 hours of sunlight
each day in winter. Near the poles, the sun sets for only a few
hours each day in summer and rises for only a few hours each
day in winter.
■✓● Reading Check How is the amount of energy received in northern
and southern latitudes different from the amount received at the
equator? (See the Appendix for answers to Reading Checks.)
352 Chapter 13 Atmosphere and Climate Change
Atmospheric Circulation www.scilinks.org
Three important properties of air illustrate how air circulation Topic: Winds
affects climate. First, cold air sinks because it is denser than Code: HE81670
warm air. As cold air sinks, it compresses and warms. Second,
warm air rises. It expands and cools at it rises. Third, warm air Ecofact
can hold more water vapor than cold air can. Therefore, when
warm air cools, the water vapor it contains may condense into Deserts Air that is warmed at the
liquid water to form rain, snow, or fog. equator rises and flows northward
and southward to 30° north and
Solar energy heats the ground, which warms the air above south latitude, where it sinks. The
it. The warm air rises, and cooler air moves in to replace it. sinking air is compressed and its
This movement of air within the atmosphere is called wind. temperature increases. As the tem-
Because the Earth rotates, and because different latitudes perature of the air increases, the air
receive different amounts of solar energy, the pattern of global is able to hold a larger quantity of
atmospheric circulation shown in Figure 3 results. This circula- water vapor. Evaporation from the
tion pattern determines Earth’s precipitation pattern. For exam- land surface is so great beneath
ple, the intense solar energy striking the Earth’s surface at the these sinking warm air masses that
equator causes the surface as well as the air above the equator little water returns to Earth in the
to become very warm. The warm air can hold large amounts of form of precipitation. Thus, most of
water that evaporate from the equatorial oceans and land. As the Earth’s deserts lie at 30° north
the warm air rises, however, it cools, which reduces some of its and south latitude.
ability to hold water. Thus, areas near the equator receive large
amounts of rain.
Figure 3 ̈ Three belts of prevailing
winds occur in each hemisphere.
Section 1 Climate and Climate Change 353
QuickLAB Global Circulation Patterns Cool air normally sinks, but cool air
over the equator cannot sink because hot air is rising below the
Investigating cool air. As a result, the cool air rises and is forced away from the
Prevailing Winds equator toward the North and South Poles. At about 30° north
latitude and 30° south latitude, some of this cool air sinks back
Procedure down to the Earth’s surface. The air becomes warmer as it
1. Cut a 20 cm diameter disk out descends. The warm, dry air moves across the surface of the
Earth and causes water to evaporate from the land below, which
of cardboard. creates dry conditions.
2. Insert a pencil through the cen-
Air descending at 30° north latitude and 30° south latitude
ter of the disk. Place the tip of either moves toward the equator or toward the poles. Air moving
the eraser on a table so that the toward the poles warms while it is near Earth’s surface. At about
cardboard is tilted slightly. 60° north latitude and 60° south latitude, this air collides with
3. Place a few drops of water near cold air traveling from the poles. The warm air rises. When this
the center of the cardboard, rising air reaches the top of the troposphere, a small amount of
and spin the cardboard on the the air returns back to the circulation pattern between 60° and
pencil tip. What happens? 30° north latitude and 60° and 30° south latitude. However, most
Analysis of this uplifted air is forced toward the poles. Cold, dry air
1. How is the motion of the water descends at the poles, which are essentially very cold deserts.
related to the prevailing winds?
EARTH SCIENCE CONNECTION
Ice Cores: Reconstructing Past Climates
Imagine having at your fingertips a ̈ With the help of ice cores, scientists are beginning to reconstruct Earth’s
record of Earth’s climate that climate history over hundreds of thousands of years.
extends back several thousand
years. Today, ice cores are providing year, one layer on top of another. ers that are deposited in the winter
scientists an indirect glimpse of Air between snowflakes and grains and in the summer. Knowing these
Earth’s climate history. These ice becomes trapped in bubbles when differences allows scientists to count
cores have been drilled out of ice the snow is compacted. These and place dates with the annual lay-
sheets thousands of meters thick in bubbles of air can provide infor- ers of ice.
Canada, Greenland, and Antarctica. mation about the composition of
the atmosphere over time. Scientists can discover impor-
How do scientists reconstruct tant events in Earth’s climate history
the climate history of our planet How do scientists date ice by studying ice cores. For example,
from ice cores? As snow falls to cores? Scientists have learned that volcanoes produce large quantities
Earth, the snow carries substances differences exist between snow lay- of dust, so a history of volcanic
that are in the air at the time. If
snow falls in a cold climate where
it does not melt, the snow turns to
ice because of the weight of the
snow above it. The substances
contained in snow, such as soot,
dust, volcanic ash, and chemical
compounds, are buried year after
354 Chapter 13 Atmosphere and Climate Change
Prevailing Winds Winds that blow predominantly in Figure 4 ̈ The red areas indicate
one direction throughout the year are called prevailing fires around Sydney, Australia, at
winds. Because of the rotation of the Earth, these about 32° south. The smoke is blown
winds do not blow directly northward or southward. by the prevailing westerly winds.
Instead these winds are deflected to the right in the
Northern Hemisphere. They are deflected to the left
in the Southern Hemisphere.
Belts of prevailing winds blow most of the time in
both hemispheres between 30° north and south lati-
tudes and the equator. These belts of wind are called
the trade winds. The trade winds blow from the
northeast in the Northern Hemisphere and from the
southeast in the Southern Hemisphere.
Prevailing winds known as the westerlies are pro-
duced between 30° and 60° north latitudes and 30°
and 60° south latitudes. In the Northern Hemisphere,
these westerlies are southwest winds. In the Southern
Hemisphere, these westerlies are northwest winds, as
shown in Figure 4. The polar easterlies blow from the
poles to 60° north and south latitudes.
̈ Whether scientists work on ice cores in the field or in the laboratory, CRITICAL THINKING
all ice cores must be handled in such a way that the cores do not become
contaminated by atmospheric pollutants. 1. Expressing Viewpoints How
might information about past car-
activity is preserved in ice cores. believe that rapid, global climate bon dioxide concentrations on
Most important, a record of con- change may be more the norm Earth contribute to scientists’
centrations of carbon dioxide, an than the exception. Evidence of understanding of present carbon
important greenhouse gas, has increases in global temperature of dioxide concentrations?
been preserved in air bubbles several Celsius degrees over several
trapped in the ice. Some scientists decades has been discovered in ice 2. Applying Ideas What informa-
who study ice cores have come to cores from thousands of years ago. tion, besides what is mentioned in
this Case Study, might scientists
learn about Earth’s climatic history
from ice cores?
Section 1 Climate and Climate Change 355
Figure 5 ̈ The El Niño-Southern
Oscillation (ENSO) is a periodic
change in the location of warm and
cold water masses in the Pacific
Ocean. The phase of ENSO in which
the eastern Pacific surface water is
warm is called El Niño, and the phase
in which it is cool is called La Niña.
Oceanic Circulation Patterns
Ocean currents have a great effect on climate because water holds
large amounts of heat. The movement of surface ocean currents is
caused mostly by winds and the rotation of the Earth. These sur-
face currents redistribute warm and cool masses of water around
the planet. Some surface currents warm or cool coastal areas
year-round.
Surface currents affect the climate in many parts of the world.
Here, we will only discuss surface currents that change their pat-
tern of circulation over time.
Figure 6 ̈ This satellite image El Niño—Southern Oscillation El Niño (el NEEN yoh) is the
shows the cool phase of the Pacific name given to the short-term (generally 6- to 18-month), periodic
Decadal Oscillation. During the cool change in the location of warm and cold water masses in the
phase, cooler water (purple and blue) Pacific Ocean. During an El Niño, winds in the western Pacific
can be seen in the eastern Pacific Ocean, which are usually weak, strengthen and push warm water
Ocean. During the warm phase, the eastward. Rainfall follows this warm water eastward and produces
situation is reversed. increased rainfall in the southern half of the United States and in
equatorial South America. El Niño causes drought in Indonesia
and Australia. During La Niña (lah NEEN yah), on the other
hand, the water in the eastern Pacific Ocean is cooler than usual.
El Niño and La Niña are opposite phases of the El Niño–Southern
Oscillation (ENSO) cycle. El Niño is the warm phase of the cycle,
and La Niña is the cold phase, as illustrated in Figure 5.
Pacific Decadal Oscillation The Pacific Decadal Oscillation
(PDO), shown in Figure 6, is a long-term, 20- to 30-year change
in the location of warm and cold water masses in the Pacific
Ocean. PDO influences the climate in the northern Pacific Ocean
and North America. It affects ocean surface temperatures, air
temperatures, and precipitation patterns.
356 Chapter 13 Atmosphere and Climate Change
Topography Figure 7 ̈ Moist ocean air moves
up the coastal side of a mountain
Mount Kilimanjaro, a 5,896 m extinct volcano in Tanzania, is range. The air cools and releases its
about 3° south of the equator, but snow covers its peak year- moisture as rain or snow. Air then
round. Kilimanjaro illustrates the important effect of height becomes drier as it crosses the range.
above sea level (elevation) on climate. Temperatures fall by When the dry air descends on the
about 6°C (about 11°F) for every 1,000 m increase in elevation. inland side of the mountains, the air
warms and draws up moisture from
Mountains and mountain ranges also influence the distribu- the surface.
tion of precipitation. For example, consider the Sierra Nevada
mountains of California. Warm air from the Pacific Ocean blows
east, hits the mountains, and rises. As the air rises, it cools, which
causes it to rain on the western side of the mountains. By the
time the air reaches the eastern side of the mountains, it is dry.
This effect is known as a rain shadow, as shown in Figure 7.
Other Influences on Earth’s Climate Figure 8 ̈ The sun has an 11-year
cycle in which it goes from a maxi-
Both the sun and volcanic eruptions influence Earth’s climate. At mum of activity to a minimum.
a solar maximum, shown in Figure 8, the sun emits an increased
amount of ultraviolet (UV) radiation. UV radiation produces more
ozone, warming the stratosphere. The increased radiation can also
warm the lower atmosphere and surface of the Earth a little.
In large-scale volcanic eruptions, sulfur dioxide gas can reach
the upper atmosphere. The sulfur dioxide gas reacts with smaller
amounts of water vapor and dust in the stratosphere. This reac-
tion forms a bright layer of haze that reflects enough sunlight to
cause the global temperature to decrease.
■✓● Reading Check How do large-scale volcanic eruptions influence
Earth’s climate?
Section 1 Climate and Climate Change 357
MATHPRACTICE Seasonal Changes in Climate
Precipitation Extremes You know that temperature and precipitation change with the
on Earth Cherrapunji, seasons. But do you know what causes the seasons? As shown in
India, which is located in Figure 9, the seasons result from the tilt of Earth’s axis (about
eastern India near the border of 23.5° relative to the plane of its orbit). Because of this tilt, the
Bangladesh, is the wettest spot on angle at which the sun’s rays strike the Earth changes as the
Earth. Cherrapunji has an annual Earth moves around the sun.
average precipitation of 1,065 cm.
Arica, Chile, is located in extreme During summer in the Northern Hemisphere, the Northern
northern Chile near the Peruvian Hemisphere tilts toward the sun and receives direct sunlight. The
border. Arica is the driest spot on number of hours of daylight is greatest in the summer. Therefore,
Earth and has an annual average the amount of time available for the sun to heat the Earth
precipitation of 0.8 mm. What becomes greater. During summer in the Northern Hemisphere, the
is the difference in millimeters Southern Hemisphere tilts away from the sun and receives less
between the annual average direct sunlight. During summer in the Southern Hemisphere, the
precipitation in Cherrapunji and situation is reversed. The Southern Hemisphere is tilted toward
the annual average precipitation the sun, whereas the Northern Hemisphere is tilted away.
in Arica?
Figure 9 ̈ Because of the Earth’s
tilt, the angle at which the sun’s rays
strike the Earth changes as the Earth
orbits the sun. This change in angle
accounts for seasonal climate differ-
ences around the world. The seasons
for the Northern Hemisphere are
shown here.
S E C T I O N 1 Review
1. Explain the difference between weather and CRITICAL THINKING
climate.
5. Making Comparisons At the equator, there are no
2. Name four factors that determine climate. summers or winters, only wet and dry seasons. Based
3. Explain why different parts of the Earth have differ- on what you have learned about atmospheric circula-
tion patterns, why do you think there are no seasons?
ent climates.
4. Explain what causes the seasons. Write a paragraph that explains your answer.
358 Chapter 13 Atmosphere and Climate Change WRITING SKILLS
6. Analyzing Processes If the Earth were not tilted in
its orbit, how would the climates and seasons be
affected at the equator and between 30° north and
south latitudes?
SECTION 2
The Ozone Shield
EARTH SCIENCE CONNECTION
The ozone layer is an area in the stratosphere where ozone is Objectives
highly concentrated. Ozone is a molecule made of three oxygen
atoms. The ozone layer absorbs most of the ultraviolet (UV) ̈ Explain how the ozone layer
light from the sun. Ultraviolet light is harmful to organisms shields the Earth from much of the
because it can damage the genetic material in living cells. By sun’s harmful radiation.
shielding the Earth’s surface from most of the sun’s ultraviolet
light, the ozone in the stratosphere acts like a sunscreen for the ̈ Explain how chlorofluorocarbons
Earth’s inhabitants. damage the ozone layer.
Chemicals That Cause Ozone Depletion ̈ Explain the process by which the
ozone hole forms.
During the 1970s, scientists began to worry that a class of
human-made chemicals called chlorofluorocarbons (CFCs) might ̈ Describe the damaging effects of
be damaging the ozone layer. For many years CFCs were thought ultraviolet radiation.
to be miracle chemicals. They are nonpoisonous and nonflam-
mable, and they do not corrode metals. CFCs quickly became ̈ Explain why the threat to the
popular as coolants in refrigerators and air conditioners. They ozone layer is still continuing
were also used as a gassy “fizz” for making plastic foams and as today.
a propellant in spray cans of everyday products such as deodor-
ants, insecticides, and paint. Key Terms
At the Earth’s surface, CFCs are chemically stable. So, they do ozone layer
not combine with other chemicals or break down into other sub- chlorofluorocarbons (CFCs)
stances. But CFC molecules break apart high in the stratosphere, ozone hole
where UV radiation, a powerful energy source, is absorbed. Once polar stratospheric clouds
CFC molecules break apart, parts of the CFC molecules destroy
protective ozone. Figure 10 ̈ The CFC molecule in
this illustration contains a single
Over a period of 10 to 20 years, CFC molecules released at chlorine atom. This chlorine atom
the Earth’s surface make their way into the stratosphere. Figure continues to enter the cycle and
10 shows how the CFCs destroy ozone in the stratosphere. Each repeatedly destroys ozone molecules.
CFC molecule contains from one to four chlorine atoms, and sci-
entists have estimated that a single chlorine atom from CFC can
destroy 100,000 ozone molecules.
Chlorine, Chlorine, Ozone, Chlorine Chlorine Chlorine,
Cl monoxide, monoxide, Ozone, Cl
Cl O3
ClO ClO O3
+
UV +
light
1 UV light causes the CFC to break 2 The chlorine atom reacts with 3 The chlorine monoxide molecule
down, releasing a chlorine atom. an ozone molecule to create then reacts with another ozone
an oxygen molecule and molecule, creating two molecules
a chlorine monoxide molecule. of oxygen and one chlorine atom.
Section 2 The Ozone Shield 359
1980 1990 2000
Figure 11 ̈ These satellite images The Ozone Hole
show the growth of the ozone hole,
which appears purple, over the past In 1985, an article in the scientific journal Nature reported the
two decades. results of studies by scientists working in Antarctica. The stud-
ies revealed that the ozone layer above the South Pole had
Connection to Meteorology thinned by 50 to 98 percent. This was the first news of the
ozone hole, a thinning of stratospheric ozone that occurs over
Polar Stratospheric Clouds the poles during the spring.
Because the stratosphere is
extremely dry, clouds normally After the results were published, NASA scientists reviewed
do not form in this layer of the data that had been sent to Earth by the Nimbus 7 weather satel-
atmosphere. However, during lite since the satellite’s launch in 1978. They were able to see the
polar winters, temperatures first signs of ozone thinning in the data from 1979. Although the
become low enough to cause concentration of ozone fluctuates during the year, the data
condensation and cloud forma- showed a growing ozone hole, as shown in Figure 11. Ozone
tion. These clouds, which occur levels over the Arctic have decreased as well.
at altitudes of about 21,000 m,
are known as polar stratospheric How Does the Ozone Hole Form? During the dark polar winter,
clouds, or PSCs. Because of their strong circulating winds over Antarctica, called the polar vortex,
iridescence, PSCs are called isolate cold air from surrounding warmer air. The air within the
mother-of-pearl or nacreous vortex grows extremely cold. When temperatures fall below
clouds. Outside of the poles, the about –80°C, high-altitude clouds made of water and nitric acid,
stratosphere is too warm for called polar stratospheric clouds, begin to form.
these clouds to form. Because
these clouds are required for the On the surfaces of polar stratospheric clouds, the products of
breakdown of CFCs, ozone holes CFCs are converted to molecular chlorine. When sunlight returns
are confined to the Antarctic and to the South Pole in spring, molecular chlorine is split into two
Arctic regions. chlorine atoms by ultraviolet radiation. The chlorine atoms rap-
idly destroy ozone. This causes a thin spot, or ozone hole, which
lasts for several months. Some scientists estimate that as much as
70 percent of the ozone layer can be destroyed during the spring.
Because ozone is also being produced as air pollution, you
may wonder why this ozone does not repair the ozone hole in the
stratosphere. The answer is that ozone is very chemically reactive.
Ozone produced by pollution breaks down or combines with
other substances in the troposphere long before it can reach the
stratosphere to replace the ozone that is being destroyed.
■✓● Reading Check What evidence showed that a hole had formed in
the ozone layer?
360 Chapter 13 Atmosphere and Climate Change
Effects of Ozone Thinning on Humans As the amount of ozone in Ozone layer
the stratosphere decreases, more ultraviolet light is able to pass
through the atmosphere and reach Earth’s surface, as shown in Ultraviolet rays
Figure 12. UV light is dangerous to living things because it damages are absorbed by
DNA. DNA is the genetic material that contains the information the ozone layer
that determines inherited characteristics. Exposure to UV light or reflected
makes the body more susceptible to skin cancer, and may cause cer- back to space.
tain other damaging effects to the human body.
Ultraviolet rays penetrate
Effects of Ozone Thinning on Animals and Plants High levels of to the Earth’s surface
UV light can kill single-celled organisms called phytoplankton that through the ozone hole.
live near the surface of the ocean. The loss of phytoplankton could Figure 12 ̈ Depletion of the ozone
disrupt ocean food chains and reduce fish harvests. In addition, a layer allows more ultraviolet (UV)
reduction in the number of phytoplankton would cause an increase radiation to reach the surface of
in the amount of carbon dioxide (CO2) in the atmosphere. the Earth.
Some scientists believe that increased UV light could be espe-
cially damaging for amphibians, such as toads and salamanders.
Amphibians lay eggs that lack shells in the shallow water of
ponds and streams. UV light at natural levels kills many eggs of
some species by damaging unprotected DNA. Higher UV levels
might kill more eggs and put amphibian populations at risk.
Ecologists often use the health of amphibian populations as an
indicator of environmental change due to the environmental sen-
sitivity of these creatures.
UV light can damage plants by interfering with photosynthe-
sis. This damage can result in lower crop yields. The damaging
effects of UV light are summarized in Table 1.
Table 1 ̄ Damaging Effects of UV Light
Humans • increased incidence of skin cancer
• premature aging of the skin
Amphibians • increased incidence of cataracts
Marine Life • weakened immune response
Land Plants
• death of eggs
• genetic mutations among survivors
• reduction of populations
• death of phytoplankton in surface water
• disruption of food chain
• reduction in the number of photosynthesizers
• interference with photosynthesis
• reduced crop yields
Section 2 The Ozone Shield 361
www.scilinks.org Protecting the Ozone Layer
Topic: Ozone Shield In 1987, a group of nations met in Canada and agreed to take
Code: HE81100 action against ozone depletion. Under an agreement called the
Montreal Protocol, these nations agreed to sharply limit their
Figure 13 ̈ Chlorofluorocarbon production of CFCs. A second conference on the problem was
production has declined greatly since held in Copenhagen, Denmark, in 1992. Developed countries
developed countries agreed to ban agreed to eliminate most CFCs by 1995. The United States
CFCs in 1987. pledged to ban all substances that pose a significant danger to
the ozone layer by 2000.
1,200
After developed countries banned most uses of CFCs, chemical
companies developed CFC replacements. Aerosol cans no longer
use CFCs as propellants, and air conditioners are becoming
CFC-free. Because many countries were involved and decided to
control CFCs, many people consider ozone protection an interna-
tional environmental success story. Figure 13 illustrates the decline
in world CFC production since the 1987 Montreal Protocol.
The battle to protect the ozone layer is not over. CFC mol-
ecules remain active in the stratosphere for 60 to 120 years.
■✓● Reading Check How did the Montreal Protocol help to protect the
ozone layer?
World CFC Production
CFC production 1,000
(in millions of metric tons)
800 Developed countries
600
400 Developing countries
200
0 1989 1990 1991 1992 1993 1994 1995 1996
1986 Year
Source: UN Environment Programme.
S E C T I O N 2 Review
1. Describe the process by which chlorofluorocarbons CRITICAL THINKING
destroy ozone molecules in the stratosphere.
5. Making Decisions If the ozone layer gets signifi-
2. Describe the process by which the ozone hole forms cantly thinner during your lifetime, what changes
over Antarctica in spring. might you need to make in your lifestyle?
3. List five harmful effects that UV radiation could have 6. Analyzing Relationships CFCs were thought to
on plants or animals as a result of ozone thinning. be miracle chemicals when they were first intro-
duced. What kinds of tests could be performed on
4. Explain why it will take years for the ozone layer to any future miracle chemical to make sure serious
recover, even though the use of CFCs has declined environmental problems do not result from its use?
significantly. Write a paragraph that explains your
answer. WRITING SKILLS
362 Chapter 13 Atmosphere and Climate Change
SECTION 3
Global Warming
EARTH SCIENCE CONNECTION
Have you ever gotten into a car that has been sitting in the sun Objectives
for a while with all its windows closed? Even if the day is cool,
the air inside the car is much warmer than the air outside. On a ̈ Explain why Earth’s atmosphere is
hot summer day, opening the door of a car can seem like opening like the glass in a greenhouse.
the door of an oven.
̈ Explain why the carbon dioxide
The reason heat builds up inside a car is that the sun’s energy content of the atmosphere is
streams into the car through the clear glass windows in the form increasing.
of sunlight. The carpets and upholstery in the car absorb the light
and change it into heat energy. Heat energy does not pass ̈ Identify one possible explanation
through glass as easily as light energy does. Sunlight continues to for the increase in average global
stream into the car through the glass, but heat cannot get out. temperature.
The heat continues to build up and is trapped inside the car. A
greenhouse works the same way. By building a house of glass, ̈ Describe what a warmer Earth
gardeners trap the sun’s energy and grow delicate plants in the might be like.
warm air inside the greenhouse even when there is snow on the
ground outside. Key Terms
greenhouse gases
global warming
Kyoto Protocol
The Greenhouse Effect Figure 14 ̈ How the Greenhouse
Effect Works
The Earth is similar to a greenhouse. The Earth’s atmosphere acts
like the glass in a greenhouse. As shown in Figure 14, sunlight
streams through the atmosphere and heats the Earth. As this heat
radiates up from Earth’s surface, some of it escapes into space.
The rest of the heat is absorbed by gases in the troposphere and
warms the air. This process of heat absorption is called the green-
house effect.
Not every gas in our atmosphere absorbs heat in this way.
The gases that do absorb and radiate heat are called greenhouse
gases. The major greenhouse gases are water vapor, carbon diox-
ide, chlorofluorocarbons, methane, and nitrous oxide. Of these,
water vapor and carbon dioxide account for most of the absorp-
tion of heat that occurs in the atmosphere.
Section 3 Global Warming 363
FIELD ACTIVITY Measuring Carbon Dioxide in the Atmosphere In 1958, a geo-
Carbon Dioxide Create a ques- chemist named Charles Keeling installed an instrument at the top
tion dealing with carbon dioxide
or carbon dioxide levels in the of a tall tower on the volcano Mauna Loa in Hawaii. Keeling
atmosphere. Investigate the FAQ
section of the Carbon Dioxide wanted to measure the amount of CO2 in the air, far from forests
Information Analysis Center’s and cities where CO2 levels vary every day. The winds that blow
Web site to see if your question steadily over Mauna Loa have come thousands of miles across
has already been answered. If
not, click on “Ask Us a Question,” the Pacific Ocean, mixing as they traveled. Keeling reasoned that
and e-mail your question to the
center. Report your findings to at Mauna Loa, the average CO2 levels in the air could be mea-
the class. sured for the entire Earth.
Most of the CO2 that is released into the air dissolves in the
ocean or is used by plants for photosynthesis. As a result, the
levels of CO2 in the air vary with the seasons. During the sum-
mer, growing plants use more CO2 for photosynthesis than they
release in respiration. This causes CO2 levels in the air to decrease
in the summer. In the winter, dying grasses and fallen leaves decay
and release the carbon that was stored in them during the sum-
mer. As a result, CO2 levels naturally rise.
Rising Carbon Dioxide Levels After only a few years of measur-
ing CO2 levels, it became obvious that they were changing in
ways other than just the seasonal fluctuations. Figure 15 shows
that CO2 levels in the atmosphere have increased by over 20 per-
cent in less than 50 years. This increase is due largely to the CO2
released into the air when fossil fuels are burned.
The data in Figure 15 provide a record of changes in CO2
levels since 1958. Levels of CO2 in the atmosphere thousands of
years ago can be determined by analyzing ice cores drilled from
ice sheets. These measurements show that CO2 levels in the atmo-
sphere today are higher than they have been for the last 420,000
years, and probably for the last 20 million years.
■✓● Reading Check What are two advantages of setting up instruments
for measuring carbon dioxide on top of Mauna Loa?
Increase in Atmospheric Carbon Dioxide, 1958–2005
380
Carbon dioxide concentration 370
(parts per million)
Figure 15 ̈ The graph shows that 360 Seasonal fluctuations
the average yearly concentration of 350 Winter (high)
carbon dioxide in the atmosphere 340
has increased since 1958. 330 Average value
320 Summer (low)
310 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005
1955 Year
364 Chapter 13 Atmosphere and Climate Change
Greenhouse Gases and the Earth’s Temperature Many scientists Table 2 ̄
think that because greenhouse gases trap heat near the Earth’s
surface, more greenhouse gases in the atmosphere will result in Major Greenhouse Gases
an increase in global temperature. A comparison of carbon diox- and Their Sources
ide in the atmosphere and average global temperatures for the
past 400,000 years supports this view. Carbon dioxide, CO2: burning
fossil fuels and deforestation
Today, we are releasing more carbon dioxide than any other
greenhouse gas into the atmosphere. Millions of tons of carbon Chlorofluorocarbons (CFCs):
dioxide are released into the atmosphere each year from power refrigerants, aerosols, foams, pro-
plants that burn coal or oil and from cars that burn gasoline. pellants, and solvents
Millions of trees are burned in tropical rain forests to clear the land
for farming. Thus, the amount of carbon dioxide in the atmosphere Methane, CH4: animal waste,
is increasing. We are also releasing other greenhouse gases, such as biomass burning, fossil fuels,
CFCs, methane, and nitrous oxide, in significant amounts. Table 2 landfills, livestock, rice paddies,
shows the sources of some major greenhouse gases. sewage, and wetlands
Global Warming Nitrous oxide, N2O: biomass
burning, deforestation, burning
Figure 16 shows that the average temperature at Earth’s surface of fossil fuels, and microbial
increased during the twentieth century. This increase is known activity on fertilizers in the soil
as global warming. Because the temperature is rising at a similar
rate to the increase in greenhouse gases in the atmosphere, many Water vapor, H2O: evaporation,
scientists have hypothesized that the increase in greenhouse gases plant respiration
has caused the increase in temperature. Thousands of experi-
ments and computer models support this hypothesis. The Figure 16 ̈ This graph shows that
increase in temperature is predicted to continue throughout the the average surface temperature of
21st century. This does not mean that temperatures are rising at Earth warmed during the 20th cen-
a constant rate, or that they are rising in all parts of the world. tury. For example, the average global
It is not possible to rule out natural climatic variability. For surface temperature in the year 2005
example, we know that fluctuations in temperatures on Earth was 0.61°C above the 20th-century
occur naturally over the centuries. average temperature.
Variation from 20th-Century Average Global Surface Temperature
0.6
Difference from 20th-century 0.3
average temperature (˚C)
0.0
–0.3
1895 1905 1915 1925 1935 1945 1955 1965 1975 1985 1995 2005
Year
Source: National Climatic Data Center.
Section 3 Global Warming 365
Figure 17 ̈ These maps were devel- Average rate of heat gain (watts per square meter)
oped from computer models. The
map on the left shows the effect of –1 0 1 2 3
greenhouse gases on the Earth
before sulfur pollution was added. Modeling Global Warming Predictions about future changes in
The map on the right shows how the climate are based on computer models. Scientists write equations
addition of the sulfur pollution vari- that represent the atmosphere and oceans. Then they enter data
able causes a cooling effect. about CO2 levels, prevailing winds, and many other variables.
The resulting models can be used to predict how factors such as
Connection to Biology temperature and sea level will be affected, as shown in Figure 17.
Ocean Warming Commercial Weather forecasters use programs similar to those used by cli-
fishing in the northern Atlantic mate scientists. You have probably been rained on when a fore-
Ocean depends heavily on a fish caster predicted dry weather, so you know that the programs and
called a cod. In recent years, the the models they produce are not always accurate. Computer
numbers of cod in the North models are becoming more reliable, however, as more data are
Atlantic have greatly decreased. available and additional variables are included.
In 2001, English scientists
embarked on a research project The Consequences of a Warmer Earth
to find out if the decline in the
numbers of cod was linked to the In North America, tree swallows, Baltimore orioles, and robins
changing global climate. They are nesting about 11 days earlier than they did 50 years ago.
sailed the ocean waters between These are birds that winter in the south and return north to breed
Greenland and Iceland collecting in the spring. In Britain, at least 200 species of plants are flower-
samples of zooplankton. The sci- ing up to 55 days earlier in the year than they did 40 years ago.
entists found that zooplankton There is no evidence that these changes are caused by global
levels have drastically decreased warming. Scientists know, however, that the time at which birds
since 1963, the date of the last nest and the time at which plants flower are both strongly influ-
survey. The scientists believe that enced by temperature.
slowly warming ocean-water
temperatures have in some way Scientists are not sure how quickly the Earth will warm or
affected zooplankton in the how severe the effects will be. Different computer models give
North Atlantic Ocean, which has different predictions. The possible effects of global warming
in turn impacted animals such as include a number of potentially serious environmental problems.
cod that rely on the zooplankton These problems include changes in weather patterns and rising
for food. sea levels. The possible effects of a warmer Earth will not be the
same everywhere. For instance, some ecosystems are less sensitive
to changes in climate than others are. Countries, too, will vary in
their ability to respond to problems caused by changes in climate.
366 Chapter 13 Atmosphere and Climate Change
Melting Ice and Rising Sea Levels Ice melts as global tempera- Figure 18 ̈ This is a satellite map of
tures increase, causing the amount of ice near the poles to an 11,000 km2 iceberg—the size of
decrease, as shown in Figure 18. The melting of ice and snow Connecticut!—that split off from the
from polar landmasses, such as Greenland and Antarctica, causes Ross Ice Shelf in Antarctica in March
sea levels around the world to rise. The rise in sea levels could of 2000.
affect coastal areas in several ways. Coastal wetlands and other
low-lying areas could be flooded. Enormous numbers of people Spider Map
who live near coastlines could lose their homes and sources of Create the
income. Beaches could be extensively eroded. The salinity of bays Graphic Organizer entitled
and estuaries might increase, which could adversely affect marine “Spider Map” described in the
fisheries. Also, coastal freshwater aquifers could become too salty Appendix. Label the circle
to be used as sources of fresh water. “Consequences of Global
Warming.” Create a leg for each
Global Weather Patterns If the Earth warms up significantly, the consequence of global warming.
surface of the oceans will absorb more heat, which may make Then, fill in the map
hurricanes and typhoons more common. Some scientists are con- with details about
cerned that global warming will also cause a change in ocean cur- each consequence
rent patterns, such as shutting off the Gulf Stream. Such a change of global warming.
could significantly affect the world’s weather. For instance, some
regions might have more rainfall than normal, whereas other Section 3 Global Warming 367
regions might have less. Severe flooding could occur in some
regions at the same time that droughts devastate other regions.
Human Health Problems Warmer average global temperatures
pose potential threats to human health. Greater numbers of heat-
related deaths could occur. Very young and very old city dwellers
are at greatest risk during heat waves. Since trees and flowering
plants, such as grasses, would flower earlier and for longer than
they do now, people who are allergic to pollen would suffer from
allergies for more of the year. As well, warmer temperatures
could enable mosquitoes—vectors of diseases such as malaria,
dengue fever, and encephalitis—to establish themselves in areas
that are too cold for them at the moment.
Figure 19 ̈ These corn plants died
from a lack of water.
www.scilinks.org Agriculture Agriculture would be most severely impacted by
global warming if extreme weather events, such as droughts,
Topic: Global Warming became more frequent. The effects of drought are shown in
Code: HE80681 Figure 19. Higher temperatures could result in decreased crop
yields. The demand for irrigation could increase, which would
Figure 20 ̈ In spite of its name, further deplete aquifers that have already been overused.
the crabeater seal actually feeds on
zooplankton. This seal is a resident Effects on Plants and Animals Climate change could alter both
of Antarctica. the range of plant species and the composition of plant communi-
ties. Trees could colonize cooler areas. Forests could shrink in the
warmer part of their range and lose diversity.
Global warming may cause a shift in the geographical range
of some animals. For example, birds in the Northern Hemisphere
may not have to migrate as far south for winter. Warming in the
surface waters of the ocean might cause a reduction of zooplank-
ton, which many marine animals depend on for food. The
crabeater seal, shown in Figure 20, would be just one of the ani-
mals affected by fewer zooplankton. Warming in tropical waters
may kill the algae that nourish corals, thus destroying coral reefs.
Recent Findings
The Intergovernmental Panel on Climate Change (IPCC) is a net-
work of approximately 2,500 of the world’s leading climatolo-
gists from 70 countries. In 2001, the IPCC issued its Third
Assessment Report (TAR). TAR describes what is currently
known about the global climate system and provides future esti-
mates about the state of the global climate system. Some of the
findings of the IPCC included that the average global surface
temperature increased by 0.6°C during the 20th century, that
snow cover and ice extent have decreased, and that the average
global sea level has risen. The IPCC has also reported that con-
centrations of atmospheric greenhouse gases have continued to
increase as a result of human activities. It has also predicted that
human influences will continue to change the composition of the
Earth’s atmosphere throughout the 21st century.
■✓● Reading Check What are two ways that drought could affect agri-
culture on a warmer Earth?
368 Chapter 13 Atmosphere and Climate Change
Reducing the Risk
In 1997, representatives from 160 countries met and set timetables
for reducing emissions of greenhouse gases. These timetables will
go into effect when a treaty called the Kyoto Protocol is ratified by
55 percent of the attending nations. The Kyoto Protocol requires
developed countries to decrease emissions of carbon dioxide and
other greenhouse gases by an average of 5 percent below their
1990 levels by 2012. In March of 2001, the United States decided
not to ratify the Kyoto Protocol. Most developed nations are going
ahead with the treaty.
The need to slow global warming has been recognized by the
global community. Some nations and organizations have engaged
in reforestation projects to reduce CO2, such as the project shown
in Figure 21. However, the attempt to slow global warming is
made difficult by the economic, political, and social factors faced
by different countries. Conflict has already arisen between devel-
oped and developing countries over future CO2 emissions, the
projections of which are shown in Figure 22.
Total World Emissions of CO2
1995 2035 Figure 21 ̈ Because plants take
in carbon dioxide during photosyn-
DEVELOPING DEVELOPED DEVELOPING DEVELOPED thesis, reforestation projects such as
this project in Haiti help to offset
COUNTRIES 27% COUNTRIES 73% COUNTRIES 50% COUNTRIES 50% a portion of global carbon dioxide
emissions.
Other Asia 6% Other
Asia Figure 22 ̈ Developing countries
Latin China U.S. 22% 14% U.S. are projected to make up half of all
America 11% 15% CO2 emissions by 2035. In 1995,
China total carbon released as CO2 was
4% 17% W. 6.46 billion tons (5.86 billion metric
Europe tons). In 2035, total carbon emis-
Africa sions are projected to be 11.71 bil-
3% 12% lion tons (10.62 billion metric tons).
Mid W. Europe Latin E. Europe/
East 17% America FSU 19%
3%
6%
Asia E. Europe/FSU
7% 27% Africa
8%
Mid East 5% Asia 4%
Source: U.S. Environmental Protection Agency.
S E C T I O N 3 Review
1. Explain why Earth’s atmosphere is like the glass in a CRITICAL THINKING
greenhouse. 5. Making Predictions Read the text under the
2. Explain why carbon dioxide in the atmosphere is heading “Modeling Global Warming.” What difficul-
increasing. ties do scientists face when they attempt to construct
models that accurately predict the rate of global
3. Explain one theory for why Earth’s climate is warming? READING SKILLS
becoming warmer.
6. Analyzing Relationships How could environmen-
4. Name some of the possible consequences of a tal problems in developing countries that result from
warmer Earth. global climate change affect the economies of devel-
oped countries, such as the United States?
Section 3 Global Warming 369
13C H A P T E R Highlights
1 Climate and Climate Change Key Terms Main Ideas
climate, 351 ̈ Climate is the long-term prevailing weather
latitude, 352 conditions at a particular place.
El Niño, 356
La Niña, 356 ̈ Factors that determine climate include lati-
tude, atmospheric and oceanic circulation pat-
terns, local geography, and solar and volcanic
activity. Latitude is the most important deter-
mining factor of climate.
̈ The angle at which the sun’s rays strike the
Earth changes as the Earth moves around the
sun. This change in angle is what causes the
seasons to change.
2 The Ozone Shield ozone layer, 359 ̈ The ozone layer in Earth’s stratosphere
chlorofluorocarbons absorbs most of the ultraviolet (UV) light from
(CFCs), 359 the sun.
ozone hole, 360
polar stratospheric ̈ Chlorofluorocarbons are human-made
chemicals that destroy ozone molecules and
clouds, 360 damage the ozone layer.
̈ Ozone levels measured over the polar regions
have been decreasing over the past several
decades.
̈ Thinning of the ozone layer increases the
amount of ultraviolet light that reaches Earth’s
surface.
3 Global Warming greenhouse gases, ̈ Gases that absorb and radiate heat in the
363 atmosphere are called greenhouse gases. The
370 Chapter 13 Highlights important greenhouse gases are water vapor, car-
global warming, 365 bon dioxide, CFCs, methane, and nitrous oxide.
Kyoto Protocol, 369 ̈ The predicted increase in global temperature
that occurs as a result of increasing greenhouse
gases in the atmosphere is called global warming.
̈ Because climate patterns are complex, scien-
tists use computer models to attempt to predict
the rate of global warming.
̈ Global warming could produce a number of
potentially serious environmental problems.
̈ In 1997, representatives from 160 countries
ratified the Kyoto Protocol, which set timetables
for reducing emissions of greenhouse gases.
13C H A P T E R Review
Using Key Terms 12. Polar stratospheric clouds convert the prod-
ucts of CFCs into
Use each of the following terms in a separate a. carbon dioxide.
sentence. b. hydrochloric acid.
c. nitric acid.
1. latitude d. molecular chlorine.
2. El Niño
3. chlorofluorocarbons 13. Which of the following is not an adverse
4. polar stratospheric clouds effect of high levels of ultraviolet light?
5. Kyoto Protocol a. disruption of photosynthesis
For each pair of terms, explain how the meanings b. disruption of ocean food chains
of the terms differ. c. premature aging of the skin
6. weather and climate d. increased amount of carbon dioxide in the
7. El Niño and La Niña atmosphere
8. ozone layer and ozone hole
9. greenhouse gases and global warming 14. In which season (in the Northern Hemisphere)
does carbon dioxide in the atmosphere
STUDY TIP decrease as a result of natural processes?
a. fall
Qualifiers When taking a test, locate qualifiers in b. winter
the sentences. Qualifiers are words that modify or c. summer
limit the meaning of another word or group of d. spring
words. Never, always, all, some, none, greatest, and
least are examples of qualifiers. 15. Which of the following gases is a green-
house gas?
Understanding Key Ideas a. carbon dioxide
b. water vapor
10. The belt of prevailing winds that is produced c. methane
between 30° and 60° north latitudes and 30° d. all of the above
and 60° south latitudes is called the
a. doldrums. 16. Which of the following substances is not a
b. westerlies. source of methane?
c. polar easterlies. a. fossil fuels
d. trade winds. b. sewage
c. fertilizer
11. Which of the following statements about El d. rice
Niño is true?
a. El Niño is the cold phase of the El 17. The average global temperature increased by
Niño–Southern Oscillation cycle. how many Celsius degrees during the 20th
b. El Niño is a long-term change in the loca- century?
tion of warm and cold water masses in the a. 0.4°C
Pacific Ocean. b. 0.6°C
c. El Niño produces storms in the northern c. 0.8°C
Pacific Ocean. d. 1.0°C
d. El Niño produces winds in the western
Pacific Ocean that push warm water 18. Which of the following countries decided not
eastward. to ratify the Kyoto Protocol?
a. Russia
b. United States
c. Canada
d. Finland
Chapter 13 Review 371
13C H A P T E R Review
Short Answer Concept Mapping ?
??
19. Name three properties of air that are impor-
tant for understanding how air circulation 28. Use the following terms to create a concept
affects global climate. map: ozone layer, ultraviolet (UV) light,
chlorofluorocarbons, polar vortex, polar
20. Explain how local geography can influence the stratospheric clouds, and ozone hole.
local pattern of precipitation.
Critical Thinking
21. Describe the properties chlorofluorocarbons
possess that made them seem like miracle 29. Making Predictions Over a long period of
chemicals when they were discovered. time, how might living things adapt to
increased carbon dioxide levels and global
22. Explain why stratospheric ozone protection warming? Do you think most species will
has been considered an environmental suc- adapt, or are many species likely to go
cess story. extinct? Write a short essay that explains
your answers. WRITING SKILLS
23. Explain the general process scientists use to
make computer models of global warming. 30. Analyzing Relationships Read about the
harmful effects that ultraviolet light can have
24. Describe some of the environmental prob- on humans as a result of ozone thinning
lems that rising sea level might cause. under the heading “Effects of Ozone
Thinning on Humans.” However, ultraviolet
25. Describe what is currently known about the light serves an extremely important function
state of the climate system as reported in that benefits life on Earth. What is this func-
the Third Assessment Report of the Inter- tion and how does it help make life on Earth
governmental Panel on Climate Change. possible? READING SKILLS
Interpreting Graphics Cross-Disciplinary Connection
The graph below shows the average monthly tem- 31. Economics Insurance companies set some of
perature of two locations that are at the same lati- their rates by estimating the number of
tude but are in different parts of the United States. destructive natural events, such as hurricanes
Use the graph to answer questions 26–27. and floods, that will occur in the next 20
26. Which location has the smallest temperature years. Explain why insurance companies
would be interested in knowing scientists’
range between summer and winter? predictions about global warming for the
27. What factors could cause the difference in next two decades.
Temperature (˚C)climate between the two locations? Portfolio Project
25 32. Designing a Pamphlet Design a pamphlet
that documents the harmful effects of ultra-
20 violet light on living things. Table 1 can be
used as a source of information. You might
15 also collect information by checking out the
Web sites of the American Cancer Society
Location B and the Environmental Protection Agency.
10 Distribute the pamphlet to your classmates,
and include it in your portfolio.
5 Location A
0
J FMAM J J A SOND
Month
372 Chapter 13 Review
MATH SKILLS READING SKILLS
33. Making Calculations In 1958, the carbon Read the passage below, and then answer
dioxide level measured in Earth’s atmos- the questions that follow.
phere was approximately 315 parts per mil-
lion. In 2000, the carbon dioxide level in the During photosynthesis, a plant takes in car-
atmosphere had increased to approximately bon dioxide from the air. Some of the carbon
368 ppm. What was the average annual in the carbon dioxide becomes part of the
increase in carbon dioxide in the atmosphere plant’s body. That carbon is not returned to
between 1958 and 2000 measured in parts the air until the leaves fall or the plant dies
per million? and decays.
WRITING SKILLS Some plants, however, never completely
decay. Instead, they are covered by sediments.
34. Communicating Main Ideas Imagine that After millions of years of being buried, the
you are a scientist who is studying the effects plants become coal, oil, and natural gas,
of chlorofluorocarbons on stratospheric which are fossil fuels. When fossil fuels are
ozone. Follow the path of a chlorine atom burned, they release the stored carbon as car-
from the time it is released into the atmos- bon dioxide. Millions of tons of carbon diox-
phere from a CFC source through the time it ide are released into the atmosphere each year
has destroyed ozone molecules. Summarize from power plants that burn coal or oil and
your findings in a brief essay. from cars that burn gasoline.
35. Writing Persuasively Imagine you are a sci- The burning of living plants also releases
entist who has been studying the subject of carbon dioxide. This process increases the car-
global warming. You have been asked by bon dioxide in the air in two ways. First, a
the President of the United States to write a burning plant gives off carbon dioxide.
recommendation for his environmental pol- Second, when a living plant is burned, there is
icy on the subject. The President has asked one less plant to remove carbon dioxide from
you to provide important facts that can be the air by photosynthesis. As millions of trees
used to promote the proposed policies. are burned in tropical rain forests to clear the
Summarize your recommendations in a land for farming, the amount of carbon diox-
brief letter. ide in the atmosphere increases.
36. Writing Persuasively You are the mayor of a 1. According to the above passage, plants
low-lying coastal town. Write a plan of give off carbon dioxide
expansion for your town. The plan should a. when they are buried under sediments.
take global warming into account. Report b. when they die and decay.
your plan of expansion in front of the class. c. when they are burned.
d. Both (b) and (c)
2. According to the passage above, which of
the following is a process that does not
add carbon dioxide to the atmosphere?
a. the decay of plants
b. photosynthesis
c. burning trees in tropical rain forests
d. burning coal in power plants
Chapter 13 Review 373
13C H A P T E R Standardized Test Prep
Understanding Concepts Reading Skills
Directions (1–4): For each question, write on a Directions (6–7): Read the passage below. Then
separate sheet of paper the letter of the correct answer the questions.
answer.
Many scientists hypothesize that the increas-
1 Which of the following is the most ing greenhouse gases in our atmosphere will
result in increasing average temperatures on
important factor in determining climate? Earth. Scientists are currently unable to make
A. volcanic activity accurate predictions about the rate of global
B. nearness to an ocean warming because climatic patterns are com-
C. distance from the equator plex and too many variables must be taken
D. atmospheric circulation patterns into account to be solved even using today’s
fastest computers. The computer models pre-
2 What causes the changes of seasons on dict how phenomena such as temperature,
rainfall patterns, and sea level, will be affected
Earth? by carbon dioxide levels, prevailing winds, and
F. the relatively constant flow of oceanic other variables.
currents Computer modeling is complicated by
G. the tilt of Earth’s axis as Earth moves Earth’s feedback systems which sometimes
make it necessary to use different equations
around the sun under changing simulated environments.
H. the distribution of precipitation
6 How could faster computers influence the
influenced by topography
I. the changes in prevailing wind patterns predictions of climate change?
A. Faster computers could produce more
at different latitudes
data.
3 The development and widespread use of B. Faster computers could solve more com-
CFCs led to what scientific discovery? plex equations.
A. CFC molecules are chemically stable. C. Faster computers could reduce the num-
B. CFC molecules contain chlorine atoms.
C. CFC molecules are destroying the ozone ber of variables needed.
D. Faster computers could increase the
layer.
D. CFC molecules are protecting the ozone degree of certainty over a prediction.
layer. 7 Assess the information needed by scientists
4 Why would global warming have an effect to build computer models that can predict
climate change.
on sea levels?
F. The warmth would cause polar icecaps Directions (8): Read the passage below. Then
answer the question.
to melt.
G. There would be widespread beach El Niño is the name given to the periodic
change in the location of warm and cold water
erosion. masses in the Pacific Ocean. During an El
H. Rainfall would increase all around the Niño, winds in the western Pacific Ocean,
which are usually weak, strengthen and push
globe. warm water eastward.
I. There would be increased cloud cover
8 How would you expect El Niño to affect
blocking the sunlight.
climate in the United States?
Directions (5): Write a short response for the
queston below.
5 The Earth’s atmosphere acts like the glass
in a greenhouse. Predict what would hap-
pen to life on Earth if Earth did not have a
greenhouse effect.
374 Chapter 13 Standardized Test Prep
Interpreting Graphics
Directions (9–11): For each question below, record the correct answer on a
separate sheet of paper.
The map below shows wind patterns across the Earth. Use this map to
answer questions 9 through 11.
Global Wind Patterns
9 Which of the following characteristics has the largest effect on wind Test
movement? Before looking at the
F. cardinal direction answer choices for a
G. latitude question, try to
H. longitude answer the question
I. seasonal change yourself.
0 Central America is located in the western hemisphere, linking North
and South America. Which way does the wind blow in Central
America?
A. northeast to southwest
B. southeast to northwest
C. northwest to southeast
D. southwest to northeast
q If you were sailing from North America to Europe, in which range of
latitudes would you sail?
F. 0° to 30°N
G. 30°N to 60°N
H. 0° to 30°S
I. 30°S to 60°S
Chapter 13 Standardized Test Prep 375
13C H A P T E R Inquiry Lab: MODELING
Objectives Build a Model of Global Air Movement
̈ Examine a model that shows how Warm air rises and cools, and cold air sinks and warms. This is
the movement of air creates a sys- true whether we are observing the temperature and air circulation
tem of wind currents on Earth. in a room or around the globe. On Earth, this movement of air
creates a system of wind currents that you will demonstrate by
̈ USING SCIENTIFIC METHODS building a model. You will build a closed system in which ice rep-
resents the polar regions and a lamp represents the equator. You
Hypothesize why the closed sys- will follow the movement of the air over these regions by watch-
tem of an aquarium is like the Earth ing a trail of smoke as it traces the path of air. (Remember that in
and its atmosphere. the global circulation pattern, warm air moving toward the poles
collides with cold air that is traveling from the poles. This colli-
Materials sion, which takes place at about 60° north latitude and 60° south
latitude, causes the warm air to rise.)
aquarium, 15 gal, glass, with
cover Procedure
goose-neck lamp, adjustable, with 1. Stack the ice cubes on the bottom of the aquarium against
a 100 W incandescent bulb one end of it. Place the lamp outside the other end of the
aquarium, and direct the bulb at the bottom half of that end.
ice cubes, large (24) Use masking tape to attach one thermometer to each end
incense stick inside of the aquarium. Make sure the thermometers can be
masking tape read from the outside of the aquarium. Place the cover on
matches the aquarium.
thermometers, outdoor (2)
2. Wait 5 minutes. Then read and record the temperature at
each end of the aquarium.
3. Light the end of the incense stick so that it produces a steady
plume of smoke.
̈ Step 1 Attach a thermometer to
each end of the aquarium, making
certain that the thermometers can
be read from the outside of the
aquarium.
376 Chapter 13 Inquiry Lab
4. Lift the aquarium cover very slightly so that you ̈ Diagramming Smoke Flow
can insert the incense stick. Hold it steadily in place Make a simple diagram of the aquar-
over the ice about 5 cm from the cover, and observe ium showing the position of the light
the smoke. source and the ice cubes. Draw
arrows to indicate the movement of
5. Observe the movement of the smoke. How does the the smoke in the aquarium.
smoke behave? Draw a diagram of the aquarium.
Use arrows to indicate the movement of the smoke
in the aquarium.
6. Remove several ice cubes and record your observations.
7. Remove all of the ice cubes and record your observations.
Analysis
1. Explaining Events Did the air movement pattern change after
some ice was removed? Explain your answer.
2. Explaining Events Did the air movement pattern change after
all of the ice was removed? Explain your answer.
Conclusions
3. Drawing Conclusions Why is the difference between tem-
peratures at the two ends of the aquarium an important
factor in the flow of heat through the aquarium?
4. Making Predictions Predict how air movement patterns will
change if polar ice begins to thaw because of global warming.
Extension
1. Analyzing Models A closed system is a collection of ele-
ments that nothing can escape from or enter. Your aquar-
ium is an example of a closed system. Convection is the
movement of warm air relative to cooler air. Discuss your
observations of convection in the closed system of the
aquarium. How can you apply this information to the
movement of air over the Earth?
2. Analyzing Models How is the Earth and its atmosphere
like the closed system of your aquarium? What factors that
affect air movement, climate, and weather exist on Earth
but not in your model?
Chapter 13 Inquiry Lab 377
EARTH SCIENCE CONNECTION
OZONE SCIENTIST study data at the National Q: How have you contributed to
Oceanic and Atmospheric the study of ozone?
Susan Solomon will not soon for- Administration (NOAA) in A: Well, when the British data
get crawling across the roof of an Boulder, Colorado. was first released, no one had
Antarctic field station in windchill much of an explanation about
temperatures of –62˚C (–80˚F), Q: What is the significance of what was causing the destruction
moving heavy equipment, and discoveries regarding the of the ozone layer. I thought
adjusting mirrors while the winds ozone hole? about the problem a lot. Later
howled and whipped about her. A: Before British scientists discov- that year, I sat in on a lecture
Sounds like an adventure, right? It ered the ozone hole in Antarctica, about types of clouds called polar
sure was! But it is just part of what no one was sure about ozone stratospheric clouds. These are
Solomon has done to establish her- changes in the atmosphere. The beautifully colored clouds that are
self as one of the world’s leading popular belief was that in 100 known for their iridescence. While
authorities on ozone destruction. years there might be 5 percent less I was looking at these clouds,
ozone. So there were questions which are common in the Ant-
Q: Is it true that you have traveled about whether it was a serious arctic but rare elsewhere, it
to the ends of the Earth to get environmental problem. But when occurred to me that they may
information about the ozone layer? the British researchers released data have something to do with ozone
A: Yes, I guess it is. My colleagues that showed 50 percent less ozone depletion. Perhaps they provide a
and I have studied the ozone hole over Antarctica in 1985 than was surface for chemical reactions that
in Antarctica, and we’ve measured present 20 years earlier, the activate reactive chlorine from
and documented ozone chemistry research raised our awareness that CFCs (human-made chlorofluoro-
above Greenland. But it’s not all the problem was far more serious carbons). If so, once activated, the
adventure. When I’m not visiting than previously thought. chlorine could contribute to reac-
one of the poles, I run computer tions that destroy ozone.
simulations of the atmosphere and
̈ The ozone hole can be seen in this satellite image. The hole is the Q: Did you get the chance to test
pale blue and black region immediately above Solomon’s shoulder. your hypothesis?
A: Yes, the next year the National
Science Foundation chose me
to lead a group of 16 scientists
for a nine-week expedition in
Antarctica. We were the first team
of scientists from the United
States sent to the Antarctic to
study the ozone hole. Within one
month we could see that unnatu-
rally high levels of chlorine di-
oxide did occur in the stratosphere
during ozone depletion. This dis-
covery was very exciting because
it seemed that we were on the
right track. We kept collecting
data that year and collected more
data during a second trip the next
year. Pretty soon, the evidence
seemed to support my hypothesis
that CFCs and ozone depletion
are linked.
378 Chapter 13 Making a Difference
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