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

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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.

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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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