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Content Benchmark E.8.A.4
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Earth Science
Atmospheric Process and Water Cycle
Solar System and Universe
Earths Composition and Structure
Content Areas
Nature of Science (NOS)
Life Science
Earth Science
Physical Science

Students understand the composition of Earth’s atmosphere, emphasizing the role of the atmosphere in Earth’s weather and climate. I/S

Life on Earth is supported by the atmosphere, solar energy, and our planet's magnetic fields. The atmosphere absorbs the energy from the Sun, recycles water and other chemicals, to provide a moderate climate. The atmosphere also protects us from high-energy radiation and the frigid vacuum of space. Earth’s atmosphere is a very thin layer of gases that surround a very large planet. An analogy of the relative diameter of the Earth compared to the thickness of the atmosphere would be to exhale onto a billiard ball (from a pool table). The billiard ball represents the Earth and the thin layer of condensation represents the relative thickness of its atmosphere.

The atmosphere makes up less than one millionth of the total mass of the Earth but is critical to life. Two gases make up the bulk of the atmosphere: nitrogen (N2) at 78% and oxygen (O2) at 21%, as indicated in Figure 1. The other one percent includes water vapor, carbon dioxide (CO2), argon, and trace amounts of other gases.

Constant components
(proportions remain the same over time and location)
Nitrogen (N2)
Oxygen (O2)
Argon (Ar)
Neon, Helium, Krypton

Variable components
(amounts vary over time and location)
Carbon dioxide (CO2)
Water vapor (H20)
Methane (CH4)
Sulfur dioxide (SO2)
Ozone (O3)
Nitrogen oxides (NO, NO2)

Figure 1. Average Chemical Composition of Earth’s Atmosphere.

Although both nitrogen and oxygen are essential to life on the planet, they have little effect on weather and other atmospheric processes. The variable components, which make up far less than 1% of the atmosphere, have a much greater influence on both short-term weather and long-term climate. For example, variations in water vapor impact relative humidity. Along with water vapor, CO2, CH4, N2O, and SO2 all have an important property: they absorb heat emitted by the Earth and thus warm the atmosphere, creating what we call the greenhouse effect. This topic is elaborated upon later in this section.

In addition to gases, the atmosphere also contains particulate matter such as dust, volcanic ash, rain, snow, and ice crystals. These are highly variable and are generally less persistent than gas concentrations, but they can sometimes remain in the atmosphere for relatively long periods of time.

Layers of the Atmosphere
Based on thermal properties (temperature trends), chemical composition, movement, and density Earth’s atmosphere is divided into four layers; troposphere, stratosphere, mesosphere, and thermosphere (Figure 2).

Figure 2. Temperature trends and layers of Earth’s atmosphere.

Beginning at Earth’s surface and extending upward to a height of somewhere between 8-16 kilometers (~5 to 10 miles), the troposphere is where almost all the weather takes place – clouds form and precipitation falls, wind blows, humidity varies, and the atmosphere interacts with the Earth below. The depth of this layer varies greatly from place to place and is influenced by unequal heating and energy transfer between Earth’s surface and the atmosphere via conduction, convection, and radiation. Its depth is greatest at the tropics where warm temperatures cause vertical expansion of the lower atmosphere. This layer decreases to a minimum depth in the polar region. The average depth of the troposphere is 11 kilometers, as indicated in Figure 2.

Temperature decreases with height (altitude) in the troposphere at an approximate rate of 6.5 degrees Celsius for every vertical kilometer traveled (known as the environmental lapse rate). As you climb higher, the temperature drops from an average of about 17°C (62°F) at Earth’s surface to -51°C (-60°F) near the top of the troposphere.

For further information on the troposphere and other atmospheric layers, visit

The stratosphere extends from the top of the troposphere (tropopause) to an altitude of 50 kilometers (~30 miles). The temperature trend within this layer is reversed from what is observed in the troposphere. In the stratosphere, as altitude increases temperature increases. The higher temperatures found in this layer occurs because of a localized concentration of ozone gas molecules (O3). These molecules absorb ultraviolet (UV) radiation generating thermal energy that warms the stratosphere. Ozone is primarily found in the atmosphere at varying concentrations between the altitudes of 10 to 50 kilometers. This layer of ozone is also called the ozone layer. The ozone layer is important to organisms at the Earth's surface as it protects them from the harmful effects of the Sun's ultraviolet (UV) radiation by absorbing it before it reaches the Earth’s surface. Without the ozone layer life could not exist on the Earth's surface.

To learn more about stratospheric ozone and the ozone layer, go to

The mesosphere (literally “middle sphere”) is the third highest layer of Earth’s atmosphere, spanning the region from 50 kilometers to 80 kilometers above the surface. The gases continue to become thinner and thinner (in other words, less dense) with height. However, the gases in the mesosphere are concentrated enough to slow down meteorites plunging toward Earth’s surface. Here is where most meteorites (shooting stars) burn up, leaving a fiery trail in the night sky. The temperature trend in this layer is reversed from what was seen in the stratosphere. Temperature decreases as altitude increases in the mesosphere. In fact, this is the coldest layer of Earth’s atmosphere where temperatures are colder than Antarctic’s lowest recorded temperature!

The thermosphere extends from the top of the mesosphere (the mesopause, at 80 kilometers) to an altitude of approximately 600 kilometers (375 miles). The temperature trend here is similar to what is observed in the stratosphere – as altitude increases, temperature increases. This is the hottest layer of our atmosphere which occurs due to the absorption of intense solar radiation by the limited amount of remaining atmospheric gases. However, in spite of the high temperature, this layer of the atmosphere would still feel very cold to our skin because of the extremely thin air (very low density of gas). The total amount of energy from the very few molecules in this layer is not adequate enough to heat our skin.

Pressure and the Atmosphere
Atmospheric pressure can be imagined as the weight of the overlying column of air. Unlike temperature, pressure decreases exponentially with altitude. Traces of the atmosphere can be detected as far as 500 km above the surface of the earth, but 80 percent of the atmosphere’s mass is contained within the 18 km closest to the surface. Atmospheric pressure is generally measured in millibars (mb); this unit of measurement is equivalent to 1 gram per centimeter squared (1 g/cm2). Other units are occasionally used, such as kilopascals, atmospheres, or millimeters of mercury (see
for a Pressure Unit Conversion Calculator).

At sea level, pressure ranges from about 960 to 1,050 mb, with an average of 1,013 mb. Fifty percent (50%) of all the molecules that make-up the atmosphere lie within the first 5.5 kilometers (18,000 feet) of Earth’s surface, and 99% lies within 30 kilometers of the ground. At the top of Mt. Everest (elevation 8,848 meters or 29,028 feet), pressure is as low as 300 mb. Because gas pressure is related to density, this low pressure means that there are approximately one-third as many gas molecules inhaled per breath on top of Mt. Everest as at sea level – which is why climbers experience ever more severe shortness of breath the higher they go, as less oxygen is inhaled with every breath.

Figure 3. Pressure and layers of atmosphere

For additional information related to Earth’s atmosphere visit

An animated diagram that allows you to investigate the height, temperature, pressure, composition, and layers of the atmosphere can be accessed at,

Atmospheric Gases and the Greenhouse Effect
In the atmospheric greenhouse effect, the type of surface that sunlight first encounters is the most important factor. Forests, grasslands, ocean surfaces, ice caps, deserts, and cities all absorb, reflect, and radiate radiation differently. Sunlight falling on a white glacier surface strongly reflects back into space, resulting in minimal heating of the surface and lower atmosphere. Sunlight falling on a dark desert soil is strongly absorbed, on the other hand, and contributes to significant heating of the surface and lower atmosphere. Cloud cover also affects greenhouse warming by both reducing the amount of solar radiation reaching the Earth's surface and by reducing the amount of radiation energy emitted into space.

For more information on the Greenhouse Effect, visit

Like the greenhouse covering, our atmosphere also serves to retain heat at the surface of the Earth. Much of the sun's energy reaches Earth as visible light. Of the visible light that enters the atmosphere, about 30% is reflected back out into space by clouds, snow and ice-covered land, water surfaces, and atmospheric dust. The rest is absorbed by the liquids, solids, and gases that constitute our planet. The energy absorbed is eventually reemitted, but not as visible light. Instead, it's emitted as longer-wavelength light called infrared radiation. This is also called "heat" radiation, because although we cannot see in infrared, we can feel its presence as heat. This is what you feel when you put your hand near the surface of a hot skillet. Certain gases in our atmosphere (known as "trace" gases because they make up only a tiny fraction of the atmosphere) can absorb this outgoing infrared radiation, in effect trapping the heat energy. This trapped heat energy makes the Earth warmer than it would be without these trace gases.

The ability of certain trace gases to be relatively transparent to incoming visible light from the sun yet opaque to the energy radiated from Earth is one of the best-understood processes in atmospheric science. This phenomenon has been called the "greenhouse effect" because the trace gases trap heat similar to the way that a greenhouse's transparent covering allows light to pass into the green house but traps heat by not letting it pass out of the greenhouse. Without our atmospheric greenhouse effect, Earth's surface temperature would be far below freezing. On the other hand, an increase in atmospheric trace gases could result in increased trapped heat and rising global temperatures. The greenhouse effect is defined as the process which causes the surface of the Earth to be warmer than it would have been in the absence of an atmosphere. If Earth’s atmosphere were removed, average temperatures would be about 30°C (50°F) lower than present.

Visit “What is a greenhouse?” for further information

Figure 4. The Greenhouse Effect.

Carbon dioxide (CO2), water vapor (H2O), methane (CH4), nitrous oxide (N2O), and a few other gases are greenhouse gases. They all are molecules composed of more than two component atoms, bound loosely enough together to be able to vibrate with the absorption of heat. The major components of the atmosphere (N2 and O2) are two-atom molecules too tightly bound together to vibrate and thus they do not absorb heat and contribute to the greenhouse effect.

For greater detail on Earth’s greenhouse gases, their source, and function in the atmosphere see

Greenhouse effect background information and links to classroom-ready activities can be found at

For an animated simulation of the Greenhouse Effect, go to

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Content Benchmark E.8.A.4

Students understand the composition of Earth’s atmosphere, emphasizing the role of the atmosphere in Earth’s weather and climate. I/S

Common misconceptions associated with this benchmark

1.Students incorrectly believe that air is not the same everywhere and that Earth’s atmosphere extends far into space.

Earth’s atmosphere is a very thin layer wrapped around a very large planet. An analogy of the relative diameter of the Earth compared to the thickness of the atmosphere would be to exhale onto a billiard ball (from a pool table). The billiard ball represents the Earth and the thin layer of condensation represents the relative thickness of its atmosphere. The actual thickness of Earth’s atmosphere is approximately 550 kilometers (350 miles), but over 99% of all gas molecules are found within the first 30 miles from the planet’s surface! Air is composed of several gases and varies in relative abundance from place to place. However, two gases make up a bulk of the Earth’s atmosphere; nitrogen (~78%) and oxygen (~21%), with much smaller amounts of water vapor, carbon dioxide (CO2), and others.

To learn more about this misconception visit

2.Students inaccurately think gases make things lighter.

Gas has mass. Gas is a phase of matter and therefore has mass and takes up space. How much something weighs depends upon how much and what kind of matter is present. Density of the material also matters. Having gas inside something does not make it lighter – although it can change its density. A possible source of this misconception is gases that students have experience with (balloons – air or helium) tend to be light. Many things that float have gas or air trapped in them (a large ship) – rather than focusing on the density of the object, which changes when the volume changes, students often focus on the air trapped inside.

Additional information related to this and other Atmosphere and Gases misconceptions visit

3.Students incorrectly think that the greenhouse effect is caused when gases in the atmosphere behave as a blanket and trap radiation which is reradiated to the Earth.

To begin with; the greenhouse effect and global warming is not the same thing. There is a greenhouse effect, which to a point is a very good thing for life on our planet; as without it the temperatures would be too cold and life could not exist (as we know it). The greenhouse effect is defined as the process which causes the surface of the Earth to be warmer than it would have been in the absence of an atmosphere. If Earth’s atmosphere were removed, average temperatures would be about 30°C (50°F) lower than present. Conversely, global warming is the term given to an expected increase in the magnitude of the greenhouse effect, whereby the surface of the Earth will almost inevitably become hotter than it is now – and occur because of the action of humans.

Our atmosphere has a profound effect on Earth’s surface temperature as seen above. The best explanation to provide students is “the surface of the Earth is warmer than it would be in the absence of an atmosphere because it receives energy from two sources: the sun and the atmosphere”.

For a complete discussion on this misconception visit

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Content Benchmark E.8.A.4

Students understand the composition of Earth’s atmosphere, emphasizing the role of the atmosphere in Earth’s weather and climate. I/S

Sample Test Questions

1st Item Specification: Understand how temperature and altitude change in the different layers of the atmosphere.

Depth of Knowledge Level 1

  1. Use the diagram below to answer the question.

Temperature Trends in Earth’s Atmosphere


  1. Which statement most accurately describes the temperature trend in the Troposphere? Temperatures
    1. rise with increasing altitude above the Earth.
    2. rise then fall with increasing altitude above the Earth.
    3. decrease with increasing altitude above the Earth.
    4. remain constant with increasing altitude above the Earth.
  1. The layers of the atmosphere are defined by
    1. altitude.
    2. temperature.
    3. gaseous composition.
    4. air pressure

Depth of Knowledge Level 2

  1. Use the diagram below to answer the question.

Temperature Trends in Earth’s Atmosphere


  1. Which list shows atmospheric temperature trends, for Earth’s four layers of atmosphere, in the correct order upward from the Earth’s surface? Temperatures
    1. decrease, increase, decrease, and increase.
    2. decrease, increase, decrease, and decrease
    3. increase, decrease, increase, and decrease.
    4. increase, increase, decrease, and increase
  1. Use the diagram below to answer the question.

Temperature Trends in Earth’s Atmosphere


  1. What do the Tropopause, Stratopause, and Mesopause all have in common? Each is a
    1. point of maximum temperature in its layer of the atmosphere.
    2. region of increasing pressure in its layer of the atmosphere.
    3. zone where both temperature and pressure fall in the atmosphere.
    4. boundary where temperature trends reverse in the atmosphere

2nd Item Specification: Recognize that the Earth’s atmosphere contains different gases and particulate matter, and is mostly nitrogen, and oxygen.

Depth of Knowledge Level 1

  1. The two most abundant gases in Earth’s atmosphere are
    1. nitrogen and carbon dioxide.
    2. oxygen and water vapor.
    3. carbon dioxide and water vapor.
    4. nitrogen and oxygen.
  1. Which gas is most abundant in Earth’s atmosphere?
    1. Carbon Dioxide
    2. Oxygen
    3. Nitrogen
    4. Ozone

Depth of Knowledge Level 2

  1. Use the graphs below to answer the question.
Diagram 1 Diagram 3
Diagram 2 Diagram 4
  1. Which pie graph best represents the relative percentage of gases in the troposphere?
    1. Diagram 1
    2. Diagram 2
    3. Diagram 3
    4. Diagram 4

3rd Item Specification: Understand the role of atmospheric gases related to the greenhouse effect.

Depth of Knowledge Level 1

  1. Carbon dioxide (CO2) in the atmosphere is most important as a(n)
    1. filter for ultraviolet radiation.
    2. absorber of heat.
    3. reflector of sunlight.
    4. shield for meteors.
  1. Carbon dioxide concentration within Earth’s atmosphere were approximately 315 parts per
    million (ppm) in 1960 and steadily rose to 355 parts per million (ppm) by 1990. The most likely cause of the overall change in the level of carbon dioxide from 1960 to 1990 is an increase in the
    1. number of violent storms.
    2. number of volcanic eruptions.
    3. use of nuclear power.
    4. use of fossil fuels.
  1. Which of the following is the most prevalent greenhouse gas?
    1. Water Vapor (H2O)
    2. Nitrogen (N2)
    3. Oxygen (O2)
    4. Hydrogen (H2)

Depth of Knowledge Level 2

  1. Use the graph below to answer the question.


  1. Provided that the current trend in atmospheric carbon dioxide (CO2) continues, what will most likely be the parts per million (ppm) in 2020?
    1. 380 ppm
    2. 395 ppm
    3. 410 ppm
    4. 425 ppm
  1. Use the graph below to answer the question.


  1. Compared to the rate at which atmospheric concentrations of carbon dioxide increased between 1850 and 1900, the rate of the increase from 1950 to 2000 has been
    1. faster, due to an increase in violent storms within the atmosphere.
    2. faster, due to an increase in the use of fossil fuels for energy.
    3. slower, as the output of solar energy from the sun has decreased.
    4. slower, due to the conservation efforts of an energy conscience population.

Constructed Response E.8.A.4

Most scientists believe the glaciers are melting because of global warming – the gradual temperature increase that has been observed with increasing urgency during the past decades. A panel of the nation’s top scientists, the National Research Council, concluded definitively that the average global surface temperatures are rising and will continue to do so.

The photos below show changes in the Qori Kalis Glacier, Quelccaya Ice Cap, Peru. The top photo was taken in 1978, and the bottom photo was taken in 2002. The glacier retreat during this time was 1,100 meters.

(Photo credit: Professor L. Thompson, Source: ScrippsNews at

  1. Explain in detail a potential cause for the significant change in the Qori Kalis Glacier during such a short time span.
  2. Describe two actions that could limit the impact humans are having on the cause listed in response A. Provide evidence as to why these actions would limit human impact.

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Content Benchmark E.8.A.4

Students understand the composition of Earth’s atmosphere, emphasizing the role of the atmosphere in Earth’s weather and climate. I/S

Answers to Sample Test Questions

  1. C, DOK Level 1
  2. B, DOK Level 1
  3. A, DOK Level 2
  4. D, DOK Level 2
  5. D, DOK Level 1
  6. C, DOK Level 1
  7. D, DOK Level 2
  8. B, DOK Level 1
  9. D, DOK Level 1
  10. A, DOK Level 1
  11. C, DOK Level 2
  12. B, DOK Level 2

Constructed Response E.8.A.4 Score Rubric:

3 points

Response addresses all parts of the question clearly and correctly.

A. The glacier has become much smaller. Rising average temperatures around the world, known as global warming, are causing many glaciers and parts of the polar ice caps to melt faster than expected. As the glacier melts, the increased amount of melt water combined with the rising temperatures will continue to accelerate the melting and retreating process.
B. Greenhouse gasses are responsible for global warming, the majority of which such as water vapor, are in the atmosphere naturally. Humans are contributing to this and can limit their impact by limiting the actions that place additional greenhouse gas emissions into the atmosphere: Reducing the burning of fossil fuels, reducing the burning of tropical rainforests, using more alternative energy sources, such as solar collectors, wind turbines, or hydroelectric, recycling more materials. Reducing the emission of greenhouse gases would decrease the concentration of heat absorbing molecules in the atmosphere; thereby diminishing heat retained cooling Earth by not absorbing or retaining as great an amount.

2 points

Response addresses all parts of the question and includes only minor errors.

1 point

Response does not address all parts of the question.

0 points

Response is totally incorrect or no response provided.

Content Benchmark E.8.A.4

Students understand the composition of Earth’s atmosphere, emphasizing the role of the atmosphere in Earth’s weather and climate. I/S

Intervention Strategies and Resources

The following is a list of intervention strategies and resources that will facilitate student understanding of this benchmark.

1.Introduction to the Atmosphere Activities

Sponsored by the National Science Foundation (NSF) and University Corporation for Atmospheric Research (UCAR), this on-line teaching module is targeted for middle school science teachers. The site provides background information and supporting classroom teaching materials. The content focus is climate change and issues related to both stratospheric and tropospheric ozone.

The Goldilocks Principle: A Model of Atmospheric Gases
Teacher’s guide to what atmospheric scientists call The Goldilocks Principle: "Venus is too hot, Mars is too cold, but Earth is just right!" Students will use similarities and differences in the atmospheres of these planets to develop an appreciation and importance of the greenhouse effect on Earth. A link to the student guide is contained within the top menu bar.

To access this activity, visit:

How High Does the Atmosphere Go?
This two-part activity demonstrates the relative thickness of the thin layer that includes the troposphere and stratosphere. Students will be able to explain how relatively thin the atmosphere is, compared to the size of the planet and will understand the relative extent of the four major atmospheric layers. A link to the student guide is contained within the top menu bar.

To access this activity, visit:

What is a Greenhouse? and What Factors Impact a Greenhouse?
These activities are designed to have students become familiar with how a greenhouse retains heat by building simple models and then exploring several factors that influence the amount of heating and cooling. A link to the student guide is contained within the top menu bar.

To access this activity, visit:

What Do Concentrations Mean? Comparing Concentrations of
Gases in our Atmosphere

In this activity, students will use a dilution experiment to understand the concept of part-per-million (ppm) and part-per-billion (ppb) measurements. Through discussion, they will be able to relate these dilutions to concentrations of gases in our atmosphere.

To access this activity, visit:

2.Atmosphere Lessons by Astrophysics Science Project Integrating Research & Education (ASPIRE)
What is this atmosphere that surrounds the Earth? This instructional tutorial, part of an interactive laboratory series, introduces students to the structure, effects, and components of the atmosphere. Here students investigate the composition of the atmosphere; effects of temperature, pressure, and ozone; the greenhouse effect; and how Earth compares with other planets. Interactive activities present students with opportunities to explore ideas and answer questions about the atmosphere, including its structure, the making of ozone, rocket launching, and measuring the atmosphere. Pop-up boxes provide additional information on topics such as dust, rain, and atmospheric composition.

Atmosphere homepage of modules is located at

Measuring the Atmosphere: Temperature, Pressure, and Ozone
In this activity you have the opportunity to ride a balloon operated by the premier hot air balloon company of the West! Today you’ve been invited to come on board with a bunch of scientists who are studying the Earth’s atmosphere. It’s not the same at different altitudes you know! You have been assigned a job by the head scientist: Measure temperature and pressure readings as the hot air balloon rises. This lesson has three main objectives; 1) Determine the relationship between atmospheric pressure and altitude. 2) Determine the relationship between temperature and altitude. 3) Determine the location of ozone in the Earth’s atmosphere.

Access this activity at

3.Weather Scope by the Center for Innovation in Engineering and Science Education (CIESE)
Weather Scope: An Investigative Study of Weather and Climate is an Internet-based multidisciplinary project which will enrich a student's learning experience through "unique and compelling" applications of instructional technology. This project is broken up into five (5) core lessons and additional supplementary and enrichment activities. These core lessons are; 1) Make a weather station 2) Using the internet to observe weather 3) Track weather like a meteorologist 4) How does the weather change? 5) Are weather forecasts always right?

To access the entire Weather Scope project including teacher guides and student activities, visit

4.The Ozone Hole Tour
This resource was created by the Centre for Atmospheric Science from the University of Cambridge, UK. The Ozone Hole Tour is a multimedia overview of the current scientific understanding of the dynamics of the hole in the ozone layer. There are four components to this tour; 1) The discovery of the ozone hole, 2) Recent ozone loss over Antarctica, 3) The science of the ozone hole, 4) Latest ozone hole research at Cambridge.

To access this resource, go to

5.Earth’s Atmosphere: Composition and
Structure Article from Vision Learning

This 5 page article provides a review of Earth’s atmospheric composition including both constant and variable components. Instruments and techniques for measuring atmospheric variables are explored including temperature and pressure trends. Several related modules and external resources are provided at the end of the article along with links for further exploration.

To access this article and supplementary resources, visit

6.Fundamentals of Physical Geography Chapter 7:
Introduction to the Atmosphere

The Fundamentals of Physical Geography (2nd Edition) online textbook describes an area of knowledge within Geography known as Physical Geography created by Dr. Michael Pidwirny at the University of British Columbia Okanagan. The Fundamentals of Physical Geography online textbook contains over three hundred pages of information and more than four hundred 2-D illustrations, photographs, and animated graphics organized into ten chapters. Important key terms in the text are linked to an interactive glossary of terms. Nested within the pages of this online textbook are links to study guide pages and additional reading pages for each chapter. Chapter 7 focuses on Earth’s atmosphere, composition and layers, greenhouse effect and global warming, and many other topics related to Earth’s weather and climate.

To explore this resource, go to

7.Encyclopedia of the Atmospheric Environment,
part of the Awesome Library

Information from this Encyclopedia focuses on nine core topic areas; Acid Rain, Air Quality, Global Warming and Ozone Depletion study the impact of mankind's pollution on the atmosphere. The Atmosphere, The Weather and The Climate investigate some of the basic physical and chemical processes which take place in the atmosphere. Climate Change looks further at natural influences on the global climate beyond man-made global warming. Finally, Sustainability is concerned with some of the solutions mankind is adopting to reduce environmental pollution, in particular the pollution of the atmosphere.

To survey this resource, visit

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Benchmark Related Vocabulary

Average precipitation
Average temperature
Cold front
Stationary front
Warm front