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Atmosphere
and Climate
A Science A–Z Earth Series
Word Count: 1,656
Atmosphere
and Climate
Written by Karen de Seve
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Atmosphere
and Climate
KEY ELEMENTS USED IN THIS BOOK
The Big Idea: Our atmosphere contains the air we breathe, keeps
the planet at a comfortable temperature, and shields us from harmful
radiation. Understanding our atmosphere helps students realize the
importance of protecting it. To reduce the release of excess greenhouse
gases, many people conserve energy, use alternative energy resources,
reuse and recycle products, and make other changes. They do so in
hopes that this planet will always be a good home.
Key words: air pressure, atmosphere, carbon dioxide, climate, condense,
dense, deserts, evaporate, exosphere, force, gases, global warming, gravity,
greenhouse effect, mesosphere, methane, molecules, nitrogen, oxygen, ozone
layer, polar zones, precipitation, temperate zones, temperature, thermosphere,
tropical zone, troposphere, water cycle, water vapor, weather
Key comprehension skills: Cause and effect
Other suitable comprehension skills: Compare and contrast; classify information;
elements of a genre; identify facts; interpret graphs, charts, and diagrams; using
a glossary and boldfaced terms; using a table of contents and headings
Key reading strategy: Summarize
Other suitable reading strategies: Ask and answer questions; connect to prior
knowledge; visualize; retell
Written by Karen de Seve
www.sciencea-z.com
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© Learning A–Z
Atmosphere and Climate
© Learning A–Z
Written by Karen de Seve
All rights reserved.
www.sciencea-z.com
Table of Contents
Introduction......................................................... 4
Earth’s Invisible Shield....................................... 5
Layers of Atmosphere........................................ 8
Earth: Just Right for Life.................................... 9
The Atmosphere and Weather......................... 11
Wind’s Driving Force....................................... 11
Water and Weather........................................... 12
A Balancing Act............................................... 14
The Atmosphere and Climate......................... 15
Climate Zones................................................... 16
Climate Change................................................. 20
Consequences of Climate Change..................... 22
Conclusion......................................................... 24
Glossary.............................................................. 25
Index................................................................... 26
3
Introduction
Look up at the sky. There’s a very thin shield
around Earth that you can’t see. It’s called the
atmosphere. It contains the air we breathe and
our weather. The shield protects us from the
harmful rays of the Sun. It helps keep our
planet warm. It makes life on Earth possible.
In this book, you will learn about Earth’s
atmosphere. You will learn about weather
over short and long periods of time. You’ll
also learn what makes up the atmosphere
and how it is changing.
4
Earth’s Invisible Shield
20
The atmosphere is like a blanket. It protects
and warms Earth’s surface. It rises more
than 700 kilometers (430 mi.) above Earth’s
surface. All the gases needed for life are in the
atmosphere. The two main ones are nitrogen
and oxygen. There are also smaller amounts of
argon, carbon dioxide (CO2), and water vapor.
We need oxygen the most. Without oxygen,
life as we know it could not exist.
18
stratosphere
50 mmHg
16
14
Altitude (km)
12
10
Mount Everest
230 mmHg
8
6
COMPOSITION OF EARTH’S ATMOSPHERE
4
2
sea level
760 mmHg
0
Scientists measure air pressure in several ways.
At sea level, air pressure is about 760 millimeters
of mercury (mmHg), or 14.7 pounds per square inch.
nitrogen
78%
Other gases,
including:
argon—0.9%
carbon dioxide—0.037%
Gases are made up of small particles called
molecules. Gravity pulls the molecules toward
Earth and packs them together. This blanket
of gas molecules creates air pressure. The air
pressure at the bottom of the atmosphere is
fairly high. The air pressure farther up in the
atmosphere is much, much lower.
oxygen
21%
The atmosphere is mostly made up of nitrogen and oxygen.
It also has small amounts of other gases.
5
6
FIVE LAYERS OF EARTH’S ATMOSPHERE
Exosphere — 10,000 km
Thermosphere — 600 km
Mesosphere — 90 km
You do not usually feel air pressure. The
pressure is the same inside and outside your
body. But when you take off in an airplane
or drive up a mountain, you go higher in the
atmosphere. The air pressure is less there. As
the air pressure outside drops, the air pressure
inside your ears stays the same. The air pushes
out from your ears and makes a popping sound.
Stratosphere — 50 km
Troposphere — 20 km
Atmosphere not to scale
Layers of Atmosphere
The atmosphere around Earth is divided
into five layers. We live in the lowest layer—
the troposphere. Earth’s weather forms
and changes in this layer.
The stratosphere is the next layer. In this
layer is the ozone layer. It protects us from
the Sun’s harmful rays. When people release
certain gases at Earth’s surface, the gases can
float up and break down ozone. Then the
ozone cannot absorb harmful rays as well.
Air pressure drops
as you climb higher.
If you climb high
enough, the air is
very spread out.
You will need
extra oxygen in
order to breathe.
The mesosphere is the middle layer, in which
most meteors burn up. Spacecraft orbit in the
thermosphere. The exosphere is the outermost layer.
7
8
Earth: Just Right for Life
COMPARING ATMOSPHERIC TEMPERATURES
Why is Earth just right for life? One
important reason is that it has water. If
Earth were too far from or too close to the
Sun, it would not have liquid water.
Another
reason is that
Why might
the atmosphere
people call Earth
works like a
a “Goldilocks planet”?
greenhouse.
A real greenhouse is a glass building that lets
in light and then traps heat. The Sun’s energy
passes through the atmosphere. Earth’s land
and oceans absorb the solar energy. This
energy warms up the land and oceans, which
warms up the air. The atmosphere traps some
of the heat, keeping it from escaping into
space. This process is the greenhouse effect.
It allows Earth to
stay warm enough
for things to live
here. (See diagram
on page 20.)
a greenhouse
9
Mars
Earth
Venus
–60ºC (–80ºF)
10˚C (50˚F)
482ºC (900ºF)
Atmospheres not to scale
The amount of heat energy trapped by
Earth’s atmosphere is just right for life. The
average temperature on Earth is 10ºC (50ºF).
Compare this to other planets. Venus is closer
to the Sun than Earth is. Its atmosphere traps
even more CO2 than Earth, so it is hot. Mars
is farther from the Sun than Earth is. Its thin
atmosphere traps very little CO2 , so it is very
cold. As far as we know, Venus is too hot for
life, and Mars is too cold.
The Moon has almost no atmosphere. The
lunar surface temperature soars to 123ºC
(253ºF) when the Sun shines on it. At night,
the Moon cools to a cold –233ºC (–387ºF) because
there is nothing to trap the Sun’s heat energy.
10
The Atmosphere and Weather
THE WATER
CYCLE
Weather happens in the layer closest
to Earth’s surface. Air in the troposphere
is always moving. It can move in every
direction. Warm and cool air mix. Areas of
high and low air pressure meet. As air moves
and mixes, it causes the weather to change.
condensation
precipitation
evaporation
snow
river
lake
ocean
aquifer
As this warm air moves away from the
warmth of Earth, it gets cooler. The molecules
move closer together. The air becomes heavier
and denser. Then the air sinks to the surface,
where it warms up again. Air rises and sinks
over and over. At
MOVING AIR CREATES WIND
the same time,
cooler
warm air
cool air
Earth is turning
cools
sinks
and pushing the
warm
cool air
air
rises
warms
air along. All this
warmer
moving air is wind.
11
respiration
surface water
Wind’s Driving Force
Air heats up as it passes over Earth’s warm
surface. The air molecules move farther apart,
meaning they are less dense. The air expands
and becomes lighter, so it rises.
water
vapor
runoff
transpiration
percolation
groundwater
Water and Weather
The water cycle begins when heat energy
from the Sun warms up lakes, rivers, and
oceans. Water molecules, like air molecules,
move apart when they are warmed. When this
happens, liquid water molecules evaporate,
or turn into water vapor. When water vapor
enters the air, it cools.
The water molecules
begin to collect on dust
When salt water
particles and condense,
evaporates from
the oceans, the salt
or form small water
is left behind. Only
droplets. Millions
the freshwater
of droplets gather
vapor rises.
together to form clouds.
12
Humidity is the amount
of water vapor in the
air at a certain location.
Tiny water droplets in the clouds join
together to become bigger droplets. Gravity
pulls these larger droplets to Earth. They can
fall as rain, snow, sleet, or hail. These are all
forms of precipitation.
A Balancing Act
Moving air and water help keep Earth
just right for living things. Air gets warmer
and cooler, but not too hot or cold for plants
and animals. Air provides a good balance of
gases, which living things need. Plants and
animals need enough water to live and grow.
Weather, the water cycle, and the greenhouse
effect are all important. They make our planet
a great home.
As moist air warms and rises over land, it cools and forms
clouds. The clouds may produce precipitation.
13
14
The Atmosphere and Climate
North Pole
Sun’s rays
Weather is what happens in the atmosphere
each day. But climate is the weather over many
years. Think about the climate where you live.
How does the temperature change over months
and seasons? How much precipitation usually
falls in a year?
WEATHER
Sun
Equator
Sunlight reaches the equator directly.
Sunlight reaches the poles less directly.
Not to scale
Climate Zones
Earth has three main climate zones. Each
climate zone is made up of several climate
types. The strength of sunlight reaching the
surface determines each climate.
The equator is a made-up line around the
middle of Earth. Near the equator, sunlight
hits Earth’s surface directly. More sunlight
gets soaked up and
changed into heat. As
a result, the climate is
warmer. The tropical zone
is warm all the time. It
often gets a lot of rain.
Rainforest climates are
found in the tropical zone.
They get rain all year long.
CLIMATE
15
16
Near the North and South Poles, sunlight
reaches the surface at a less direct angle. As
the energy passes through a lot of atmosphere,
it gets weaker.
As a result, the
climate in the
polar zones is
much colder
than in other
zones. Some
polar climates
are very cold
and dry. They
only get a little snow, and it does not melt.
All this snow has formed ice sheets over
many, many years. Another polar climate
is called tundra. It is not as cold, and its
ice sometimes melts.
North and south of the tropical zone are
the temperate zones. During summer, sunlight
hits the surface more directly, so the weather
is warmer. During winter, the Sun’s rays strike
less directly, so it is cooler. The temperate zones
are warm during the summer and cold in the
winter. But not all temperate climates are the
same. They can be dry or humid, warm or cold.
17
The coldest temperature
ever recorded on Earth
was in Antarctica,
near the South Pole.
That temperature was
–89.2ºC (–128.6ºF).
18
Climate Change
CLIMATE ZONE MAP
60˚N
30˚N
Equator 0˚
30˚S
60˚S
Key
Tropical Zone
Temperate Zone
Polar Zone
Some kinds of climates are found in more
than one climate zone. For example, deserts
can be found in all three climate zones. Deserts
are very dry. Most people think all deserts are
hot, but some deserts are cold. Even in hot
deserts, the temperature at night can be very
cold, especially in winter. The deserts with the
least rain are called arid. Other deserts, which
get more rain, are called semi-arid.
If the whole Earth were covered
with desert sand, it would actually
be cold, not hot. A sandy surface
reflects most of the Sun’s energy
instead of absorbing it.
Changes in the atmosphere can cause
changes in the climate. Until recently, the
atmosphere had just the right amount of gases
and dust to trap the heat energy reflected from
Earth. But in recent years, more heat is being
trapped. During this time, people have been
burning lots of coal, gas, and oil. We use these
fuels to heat buildings, run vehicles, and make
products. Burning these fuels adds certain gases,
called greenhouse gases, to the atmosphere.
Are these gases making the planet warmer?
energy emitted
into space
trapped energy
Sun
solar energy
Earth
atmosphere
Not to scale
More solar energy is trapped by Earth’s atmosphere now
than in the past.
19
20
Consequences of Climate Change
When coal burns, it gives off carbon dioxide
(CO2). We mainly use coal to make electricity.
Oil is another fuel that people burn. It doesn’t
give off as much CO2 as coal. But it still adds
greenhouse gases to the atmosphere.
Temperature in °F
During digestion,
cows, sheep, and
goats release
methane, a
greenhouse gas.
58.0°
360
57.5°
340
57.0°
320
Temperature
56.5°
300
56.0°
280
CO2
55.5°
1000
260
1200
1400
1600
1800
2000
Year (AD)
In recent years, there has been a sharp rise in greenhouse
gases in the atmosphere. During the same time, average global
temperatures have risen.
21
22
CO2 Concentration in PPM (parts per million)
Scientists have
found that the recent
rise in CO2 is causing
the atmosphere to trap
more heat. As a result,
temperatures are rising
all around the planet.
This change is called
global warming.
The world’s average temperature has only
risen a little bit (about 0.6°C or 1°F). But this
change has made a big difference. Global
warming is making the weather change in
some places. More and more huge storms have
happened, causing flooding and erosion. Heat
waves that cause drought are more common.
Places that used to be green are now dry and
bad for farming. In the polar zones, ice is
melting, and some polar animals may not
survive. Many huge glaciers have melted to a
much smaller size. Others are completely gone.
Conclusion
Polar bears depend on sea ice for hunting and raising their
babies. If the sea ice keeps melting, polar bears might not survive.
Scientists say we cannot fix the mixture of
gases in the atmosphere. But we may be able
to slow down the change. We can use wind
and solar power to make electricity. We can
drive hybrid and electric cars instead of using
so much oil and gas. We can build buildings
that use less energy to heat and cool. We can
carpool, walk, ride bikes, and use buses and
trains to avoid burning so much fuel. All these
actions can help limit the amount of harmful
gases we put into the atmosphere.
23
Look up at the sky again. Do you think
about our atmosphere in a new way?
Scientists are trying to understand how
Earth’s shield forms. They are also studying
how it is changing. They suggest how people
can help keep climate change from getting
worse. Even small
changes can be very
harmful for our planet.
The future of Earth and
everything that lives on
it depends on a healthy
atmosphere.
Take Action!
Here are a few things people are doing to cause
less climate change. Think about how
each action might help.
• Waste less electricity.
• Use reusable shopping bags.
•D
rive less.
•R
educe waste
and reuse and
recycle products.
24
Glossary
atmospherethe mass of air around Earth (p. 4)
temperate zonesEarth’s climate zones located
between the tropical and polar
zones, where the sunlight angle
causes warmer summers and
cooler winters (p. 17)
climatethe weather conditions in an area
over a long period of time (p. 15)
temperaturethe measurement of how hot
or cold something is (p. 10)
gasesmatter that can freely change shape
and size; often can’t be seen (p. 5)
tropical zoneEarth’s warmest climate zone,
located near the equator, where
sunlight strikes the planet’s
surface most directly (p. 16)
air pressurethe force that air puts on an object
(p. 6)
global warmingan increase in the average
temperature of Earth’s atmosphere
and oceans, especially one great
enough to change the climate (p. 21)
greenhouse effectthe process by which heat is trapped
inside Earth’s atmosphere by gases
(p. 9)
moleculesthe smallest parts of substances
that can exist by themselves,
made of two or more atoms (p. 6)
ozone layera layer of the atmosphere that
protects life on Earth by filtering
out ultraviolet radiation from the
Sun (p. 8)
polar zonesEarth’s coolest climate zones,
located near the poles, where
sunlight strikes the planet’s surface
at a low, slanting angle (p. 18)
precipitationwater that falls from clouds in the
form of rain, snow, sleet, or hail
(p. 13)
stratospherethe layer of Earth’s atmosphere
located beyond the troposphere;
the layer that protects Earth from
solar radiation (p. 8)
25
tropospherethe layer of Earth’s atmosphere
closest to the planet’s surface;
the layer in which weather takes
place (p. 8)
water cyclethe path water takes, and the
changes it goes through, as it
moves on, above, and below
Earth’s surface (p. 12)
weathera description of the temperature,
clouds, rain, wind, and other
conditions in the air at a certain
time (p. 4)
Index
carbon dioxide (CO2),
5, 10, 21, 22
desert, 19
gravity, 6, 13
rainforest, 16
Sun, 4, 8–10, 12,
16–19
methane, 21
water vapor,
5, 12, 13
nitrogen, 5
wind, 11, 23
oxygen, 5, 7
26