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Earth’s climate is a balance between how much energy is received from the Sun and how much energy leaves Earth. Climate change happens any time the balance is altered.
NATURAL CAUSES OF CLIMATE CHANGESometimes Earth receives more energy from the Sun than usual. The Sun has active periods during which it gives off more energy than at other times. There is evidence that these periods, which occur in cycles of about 11 years, correspond to warming trends on Earth.
The tilt of Earth’s axis also changes the amount of energy received from the Sun. The tilt of Earth’s axis ranges from 22° to 25° in a 41 000-year cycle. The differences in tilt could change climate conditions. Locations tilted closer to the Sun will warm. Locations tilted farther from the Sun will cool.
Volcanic eruptions can throw huge amounts of dust and ash high into the atmosphere (Figure 2.22). This dust and ash can remain there for months or even years. This material reflects solar energy back into space, reducing the amount of heat entering Earth’s climate system.
WHAT CAUSES
CLIMATE CHANGE?
FIGURE 2.22 Mount Pinatubo in the Philippines erupted in 1991. The ash cloud was so large that it lowered the global average temperature for a period of one to three years.
I wonder what other effects this volcanic eruption caused?
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THE GREENHOUSE EFFECTNatural events such as volcanic eruptions release huge amounts of greenhouse gases into the atmosphere. Greenhouse gases are gases that absorb energy from the Sun. Greenhouse gases include CO2, methane, and ozone. These gases have the same effect on Earth as glass does in a greenhouse. The Sun’s energy passes through the glass of the greenhouse and some of it becomes trapped inside to warm the plants. In the same way, the Sun’s energy passes through Earth’s atmosphere. The greenhouse gases prevent some of the energy from going back into space, and the trapped heat warms Earth (Figure 2.23). The greenhouse effect is an important natural process. It helps keep Earth warm enough to support life. However, if the amount of greenhouse gases increases, more of the Sun’s energy gets trapped in Earth’s system. It changes the balance between incoming and outgoing energy, and can cause climate change.
The average temperatures on Earth’s surface increased by 0.8 degrees Celsius in the past 100 years. But in the past 66 years, between 1948 and 2013, the average temperature in Canada warmed by 1.6 degrees Celsius. More greenhouse gases in the atmosphere have caused the average temperature to rise.
FIGURE 2.23 The greenhouse effect traps warmer air close to Earth. Without the greenhouse effect, the average temperature on Earth would be about 33 °C colder than it is now.
greenhouse gases gases in the atmosphere that contribute to the greenhouse effect by absorbing energy from the Sun; they include CO2, methane, and ozone
atmosphere
Some sunlight is reflected back to space by the atmosphere.
Some sunlight passes through the atmosphere to warm Earth’s surface.
Greenhouse gases in the atmosphere trap some of the radiated thermal energy, keeping Earth warm.
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HUMAN ACTIONS CAUSING CLIMATE CHANGEScientists agree that global warming is related to the rising amounts of greenhouse gases in the atmosphere (Figure 2.24). Where are these extra greenhouse gases coming from? Scientists have considered both natural and human-made sources of greenhouse gases. The increase in CO2, the most common greenhouse gas, began with the widespread use of fossil fuels in the 1800s. Fossil fuels are fuels obtained from beneath Earth’s surface. Examples of fossil fuels include oil, natural gas, and coal. You will learn more about these in Chapter 8.
HUMAN-MADE SOURCES OF GREENHOUSE GASESWhat human activities produce greenhouse gases? Most people would say energy production and transportation. But many other human activities also produce greenhouse gases (Figure 2.25). The major human activities that produce greenhouse gases include the following:• Electricity production: We burn fossil fuels, such as natural gas, oil,
and coal, to produce electricity. • Transportation: Most cars, trains, ships, and planes are powered by fossil
fuels, such as gasoline and diesel. • Industry: Many industries, such as the steel industry, use fossil fuels to
produce heat for making products. • Homes and businesses: Fossil fuels are burned for heat. Some
of the chemicals we use in our homes or businesses, such as the coolants in refrigerators, also give off greenhouse gases.
• Agriculture: Greenhouse gases are produced in animals’ digestive tracts and emitted into the air. They are also given off when animal waste decays. The decaying of unused plant materials, such as waste from food crops, also produces greenhouse gases.
• Waste: Household wastes and industrial wastes release greenhouse gases as they decompose.
fossil fuels fuels, such as oil, natural gas, and coal, formed millions of years ago from the remains of plants and animals
C02-F19-G07SB
Crowle Art Group
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Years
CO2 Levels in the Atmosphere
1010 1110 1210 1310 1410 1510 1610 1710 1810 1910 20100
50
100
150
200
250
300
350
400
CO
2 (p
arts
per
mill
ion)
FIGURE 2.24 This line graph shows CO2 levels in the atmosphere from 1010 to 2010.
What might be some ways of reducing our use of fossil fuels for transportation?
FIGURE 2.25 Energy production and transportation are major sources of greenhouse gases. However, other human activities are also a significant source of greenhouse gases.
C02-F20-G07SB
Crowle Art Group
1st pass
Geography 7 SB
0-17-659048-X
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transportation24%
homes andbusinesses12%
industry11%
agriculture10%
waste7%
Canada’s Greenhouse Gas Emissions, 2011
energyproduction
36%
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HEROES IN ACTION
A CALL TO ACTION 1. Think about some environmental
challenges you care about. What are
some ways you can contribute?
2. How can you raise awareness of
global warming in your community?
How would you try to reach a more
global audience?
Alec Loorz (Figure 2.26) became a climate
activist at the age of 12. Inspired by the
documentary An Inconvenient Truth, Loorz
wanted to contribute to a solution to
global warming. He tried to join different
organizations but they turned him away,
saying he was too young. So Loorz started
his own organization when he was 13: Kids
vs Global Warming. “I used to play a lot of
video games, and goof off, and get sent
to the office at school,” he
said. “But once I realized it
was my generation that
was going to be the first
to really be affected by
climate change, I made up
my mind to do something
about it.”
Through his organization,
Loorz has spoken all over the world to
hundreds of thousands of people on the
subject of global warming. Through the
iMatter campaign, Kids vs Global Warming
is also empowering young people to take
a leadership role in addressing climate
change. The goal of the campaign is to
create a youth climate movement. Young
people will help create awareness by
educating their peers, politicians, and
the general public through speeches
and presentations, and through the
international iMatter march. Loorz has
done more than give speeches. He also
sued the United States government.
In 2011, Loorz, along with four other
teenagers in the organization, filed a
lawsuit to try to force the U.S. government
to reduce the nation’s CO2
emissions. They wanted
reductions of at least
6 percent per year
beginning in 2013. The
teens also wanted to make
people across the country
aware that the United
States had made little
progress in dealing with climate change. In
an interview about the lawsuit, Loorz said,
“I think a lot of young people realize that
this is an urgent time, and that we’re not
going to solve this problem just by riding
our bikes more.” Although the lawsuit was
dismissed, Kids vs Global Warming filed
an appeal in 2013. They continue to seek a
way to hold the government accountable
for the impact of their decisions on
the climate.
ALEC LOORZ: KIDS VS GLOBAL WARMING
FIGURE 2.26 Environmental activist Alec Loorz
“WE’RE NOT GOING TO SOLVE THIS PROBLEM JUST BY RIDING OUR
BIKES MORE.”
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TAKING ACTION AGAINST CLIMATE CHANGEHow should we deal with climate change? This has been debated by many scientists, governments, and concerned citizens around the world. Not everyone agrees that action should be taken. Some people feel that climate change is a natural process and there is nothing we can do. Others doubt that climate change is real, or that humans are causing it.
However, most geographers and other scientists agree that human actions are a cause of climate change. As you learned earlier in the chapter, we will feel the impacts of climate change in the coming years. People need to take action now to address the effects of climate change. There are two ways we can deal with climate change: mitigation and adaptation.
MITIGATIONMitigation means reducing the consequences of a problem. To mitigate climate change, we must act on its causes. One of the key greenhouse gases we produce is CO2.
Why might some people argue
that climate change is unimportant or that we should not do anything
about it?
mitigation action taken to reduce the consequences of a problem
FIGURE 2.27 Greenacre Park in New York City is an example of a pocket park. New York City was one of the first cities to create pocket parks.
How could a pocket park benefit my community?
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By making different choices, we can reduce CO2 levels in the atmosphere. Here are some examples of actions we can take to help mitigate the problem:• switch from fossil fuels to other forms of energy such as solar or wind• drive a fuel-efficient car, ride a bike, or walk instead of driving• reduce your energy use, such as by turning off the lights when no one is in
the room• preserve green spaces or plant more trees to absorb greenhouse gases• use technology to capture CO2 emitted from smokestacks • consume locally made products instead of products that come from
far away• reduce, reuse, and recycle to reduce the amount of energy used to
manufacture new products• conserve water by using less or using it more efficiently
ADAPTATIONAn adaptation is a change made to deal with a new situation. In the case of climate change, we must adjust to the effects of climate change to try to protect ourselves and our planet.Some adaptations include• growing crops that will adapt and grow in the new climate• expanding healthcare to treat or prevent health problems caused by
extreme weather events such as heat waves• protecting water sources from the effects of warmer temperatures and
extreme weather, for example, by building larger storage places• building more parks and green spaces in cities where people can cool off
Figure 2.27 shows an example of a pocket park. Pocket parks are small-scale urban parks that can be built in small spaces—in abandoned lots, in between buildings, or in former parking lots. Cities are adopting these pocket parks as a way to increase green spaces.
1. INTERRELATIONSHIPS In a sentence or two, explain
the differences between mitigating a problem
and adapting to a problem.
2. INTERPRET AND ANALYZE Think about what you
know or have learned about extreme weather.
Identify two actions that people could take to
mitigate the problem and two actions that would
help them adapt to the problem.
3. COMMUNICATE Suppose you read an ad claiming
that climate change is not a big problem and
so we should do nothing about it. Create an ad
in reply. Be sure to provide evidence to support
your opinion.
CHECK-IN
adaptation a change or adjustment made to deal with a new situation
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