Lesson 1

Environmental Change - Or Not?


Lesson Overview:

Lesson 1 discusses: 1) global climate patterns over time; 2) indications of possible climate change; 3) anthropogenic contributions to climate change.


Learning Objectives:

Students will:

  • Define vocabulary words from the lesson.
  • Name at least two indications Earth's climate may be changing.
  • Recall one natural influence on climate.
  • Identify one or more human activities that may contribute to climate change.


Content Standards Addressed:

Common Core State Standards



Albedo - percentage of light reflected from a surface.
Anthropogenic - caused by humans.
Geologist - scientist who studies the earth's history, formation, etc.
Glacial epoch - a period characterized by expanses of ice that grow and reduce in size in cycles.
Greenhouse effect - the trapping of heat in Earth's atmosphere due to naturally present gases like CO2.
Interglacial - relatively warmer period of time between two glacial periods.
Saline - containing salt.
Special Note: Young children are very impressionable. If presenting Lesson 1 to children who are younger than middle school age, please spotlight the following:
  • There is a debate as to whether climate change is a serious problem. We can all agree, however, that protecting our environment is important.
  • Scientists and others who believe climate change is occurring are now taking steps to battle the problems associated with it, so worst-case scenarios do not occur.
  • It's OK to be concerned about climate change. When people are concerned, they may take needed steps to change their behaviors and may be motivated to persuade others to change as well.
  • Young people are not responsible for taking the most critical steps to combat climate change; however, people of every age have parts to play. Making changes to our personal lives at home, school, and in our communities, and persuading others to make lifestyle changes as well are important, positive steps.


Imagine Earth as a lifeless, cold ball of rock. What makes our planet so livable?

Scientists tell us Earth's atmosphere supports life as we know it because of the "greenhouse effect." The sun warms our planet during the day. At night some of this solar energy is radiated back into the atmosphere as infrared waves. The gases naturally found in the atmosphere, including carbon dioxide, methane and nitrous oxide, absorb some of the energy, helping to keep heat in. Without them, the earth's temperature would be about 60 degrees cooler.
Some experts say the greenhouse effect is misnamed. A greenhouse is a glass-enclosed room or building that keeps outside air from coming in and inside air from escaping so plants may be grown in any season. If the earth's atmosphere only trapped heat, we would observe rising temperatures, but in reality they are rather steady.
For hundreds of years, "greenhouse gases" have been accumulating in increasing amounts, which has enabled Earth's atmosphere to retain even more solar energy, causing what is termed "global warming" by some. Scientists prefer "climate change" or "climate disruption" over "global warming," because those terms also include precipitation, extreme weather, etc.
Geologists (scientists who study the earth's history, formation and other qualities) tell us that climate, like the Earth itself, is always changing. Scientists can estimate what the global climate was like long ago by examining tree rings, ice cores, coral skeletons and other sources. Over time, climate changes force species to adapt or face extinction.

FYI: What's the difference between weather and climate?

Weather refers to day-to-day changes in temperature, humidity and precipitation over days, months or even years.

Climate takes note of temperature, humidity and precipitation in a longer time frame - over decades or centuries.

Unusual weather shouldn't be interpreted as climate change unless it occurs consistently for more than a decade or longer.


Special note: Scientists have attempted to date the earth by various means, and opinions vary as to its age. You may choose to share or skip the brief section below. 


Climate change is not unique to the 20th and 21st centuries. If you could somehow rewind more than four billion years of Earth history, you would notice that much of the time our planet has had no ice. But at times large expanses of ice known as glaciers have covered the earth, increasing and decreasing in area in cycles. These periods of time are known as glacial epochs.

The Pleistocene glacial epoch began more than 2.5 million years ago. During the Pleistocene, ice-covered, or glaciated, areas of the earth grew or receded in cycles of hundreds of thousands of years. The southernmost reach of the glaciers here in the U.S. has at times covered nearly all of Illinois and Iowa. Thousands of years from now, Earth may once again return to an "ice age" like the one that ended about 10,000 B.C.

  • The NOAA (National Oceanic and Atmospheric Administration) website shows how the earth's ice fields have changed over time. Keep the first world map "Modern," but change the second map using the drop-down menu. The greatest extent of the glaciated (ice-covered) areas in recent times occurred about 21,000 years ago.

The earth entered the Holocene Epoch about 12,000 years ago and is in the midst of a relatively warmer stage called an interglacial. Interglacials were once thought to have a fairly stable climate but, by sampling deep-sea cores, scientists have discovered warming and cooling also occurs in cycles during these periods of reduced ice cover. In the last thousand years, the earth has experienced a "Medieval Warm Period" (1000-1350 A.D.), a "Little Ice Age" (1400-1860 A.D.), and "Industrial Age Global Warming (from the late 1800s to present day). Scientists say as long as the South Pole's ice cap remains, the earth will continue cycling through glacial and interglacial periods of time.

What evidence do some experts use to point to climate change occurring?
  • Changing hardiness zone maps. Hardiness zone maps are designed for use by gardeners and show the lowest extremes of temperature in various locations of a country. Some plants that were formerly not recommended for a certain area of a country may in some cases now be successfully grown in those areas.
  • Earlier seasonal events. Egg-laying and leaf-unfolding are observed to be happening earlier.
  • Shifting migration patterns. Birds and butterflies are traveling less further south and to higher altitudes to spend winters. (See the National Audubon Society's bird migration map.)
  • Abnormal precipitation. Bouts of heavy precipitation have increased in some vulnerable areas. (Warmer temperatures increase the amount of water vapor in the atmosphere, leading to more precipitation.) Drought (including bouts of extreme drought) has increased in some drought-prone areas.
  • Increase in record-setting temperatures. Record highs and warmest years are happening more often in some areas.
  • Longer growing season. In some areas, spring warming is happening earlier and first frost dates are occurring later in the fall.
  • Rising incidence of disease. Diseases that thrive in warmer temperatures, like malaria, have increased in some areas not usually associated with them.
  • Increase in ice melting. Glacial ice is melting, causing sea levels to rise slightly. (Sea ice is also melting, but this does not affect sea levels.) As water levels rise, some coastlines are changing due to beach erosion, and salt water is threatening some freshwater sources.
  • Changes in water. Carbon dioxide dissolves in water, becoming carbonic acid. Oceans and organisms that live in them can absorb much more carbon dioxide than the atmosphere contains, but increases in levels of carbon dioxide are causing oceans to become more acidic. 


Reproducible: Simple Science: Melting Ice 

Students may wonder why melting glacier ice causes sea levels to rise, but melting sea ice does not. They can do a simple experiment illustrating this curiosity. Make copies of the reproducible. You'll also need one or multiple sets of the following:

  • A large, flat-bottomed, clear plastic or glass measuring cup (or similar container).
  • Two large chunks of ice.
  • An unopened soup can with label removed (size will depend on measuring cup/container used).

Students will note the water level rose in the second experiment, but not the first. Why? The ice chunk that floated in the water is like sea ice, which moves (or displaces) the water in which it floats. When the ice melts, there is no change in the level of water.

The ice chunk resting on the soup can is like glacier ice. Since the ice is on the land (the soup can, in the experiment), not in the water, no water is displaced. When the ice melts into the water, it increases the amount of water in the ocean (the container), causing the water level to rise.



As a follow-up to the experiment, have students research the potential impact of rising sea levels here in the United States. How might this affect:

  • Ecosystems?
  • Agriculture?
  • The economy?
  • Water quality and supplies?


Reproducible: Simple Science: Arctic Amplification

The percentage of sunlight reflected from a surface is known as its albedo. Glaciated (ice-covered) surfaces have high albedo. Light-colored, they reflect more solar energy and keep surrounding areas cooler. Dark surfaces have low albedo. They absorb more solar energy and warm the surrounding area. Because areas of melted ice are darker within a landscape, they absorb, rather than reflect, the sun's warming rays, and actually accelerate the melting of glaciated areas nearby. This is called arctic amplification. Make copies of the reproducible and allow the students to observe arctic amplification by conducting the experiment.

  • How might a knowledge of albedo help city planners as they prepare for climate change and a warmer future? Are any steps being taken in the city area nearest you? Possible answers may include providing additional green space (shade trees, etc.) and mandating solar-reflecting roofs and light-colored pavements. How effective would these steps be, in the students' opinions?


Reproducible: Simple Science: Saline Levels and Plant Growth

For many reasons, soils are becoming more saline. How do commonly-grown crops like beans react to increasingly saline conditions? Your students can find out by doing this experiment.

Make copies of the reproducible. You'll also need: 

  • Pinto or other dried beans (at least one per student).
  • Water.
  • Paper towels.
  • Plastic zip bag.
  • Small plastic or clay pots, one per student.
  • Potting soil.
  • Measuring spoons.
  • Salt.
  • 2-liter plastic bottles, emptied and cleaned.

Divide the students into five groups, according to the type of solution they'll use to water their plants:

  • Group A: plain  tap water.
  • Group B: 1/2 teaspoon salt/1 quart tap water.
  • Group C: 1 teaspoon salt/1 quart tap water.
  • Group D: 2 teaspoons salt/1 quart tap water.
  • Group E: 4 teaspoons salt/1 quart tap water.

Follow up:

  • What conclusions about salinity and plant growth can be drawn from the experiment's results? Invite students to do research. Does the research support their conclusions? Be sure to mention salinity interferes with plant osmosis, if students don't uncover the fact.
  • If time permits, repeat the experiment with sorghum, sugar beet or pearl millet seeds. Did the experiment results differ? How? Invite students to research the types of plants that were used in order to understand why the outcomes were different. (Hint: Use keywords glycophytes and halophytes.)
  • What agricultural changes are experts predicting in the next century for the United States? Which geographical areas in particular may be affected? What crops may be at risk?
  • Agricultural researchers are exploring alternative crops that can be grown under saline conditions. Have students research which seem most promising for future livestock and human use.

Many experts agree the global climate is changing. However, it's difficult to determine how current changes compare with those of the past because dependable weather records are not available for earlier periods. Scientists don't know all the reasons climate change occurs, but they do know climate is influenced by:

  • Tectonic changes, changes in the earth's structure. This includes the movement of the continents and the sea floors, which cause changes in ocean currents.
  • Astronomic changes, like changes in Earth's orbit, the tilt of its axis (it has a slight "wobble"), its gravitational and magnetic fields, and solar activity.
  • Atmospheric changes, changes in the gases that surround Earth. These changes include increases in carbon dioxide and methane, clouds, dust from volcanoes, and changes in the ice caps at the earth's poles.

A heated debate has arisen as to why climate change is happening now and in such a short time frame. On one side of the debate are those who claim the observed changes are occurring naturally, as they have for billions of years. (Increases and decreases in solar activity - which happen in cycles - volcanic eruptions and climate patterns over the ocean can all affect temperatures.)
On the other side of the debate are those who say the changes are anthropogenic - caused by humans. (Anthropo- means "human"; - -genic means "produced or caused by.") Scientists who believe anthropogenic climate change is now occurring are alarmed about how quickly the observed changes seem to be happening. They say previous climate change occurred over thousands of years. (Some experts, however, point climate change can happen rapidly, for instance, when ocean currents are disrupted.) Though it's difficult to fully understand how much human activities influence climate, some experts say the following have most contributed to climate change.
  • Generating electricity. Most power plants still use coal, which is more polluting than natural gas or oil. There is also an environmental cost of retrieving these fossil fuels from the earth: the emission of carbon dioxide into the atmosphere. Fossil fuels provide 85 percent of our total energy needs.
  • Farming and raising livestock. Field machinery operation, fertilizer production and emissions from livestock and their waste all contribute. In addition, farming and raising livestock requires clearing the land of trees and other vegetation, which would normally absorb and store about 2,700 pounds of carbon dioxide and other harmful gases per acre, per year.
  • Transportation. Gasoline-burning cars, and diesel trucks and buses, all contribute carbon dioxide to the atmosphere. Land developers now create residential areas that force people to rely on private autos instead of public transportation like commuter trains and buses. Also, newer residential areas may not have sidewalks; this discourages walking.
  • Manufacturing. Since the mid- to late-1700s, beginning with textile manufacturing and iron making, people have used machines to do work previously done by hand. The Industrial Revolution was powered, not by wind, water and wood as in the past, but by the plentiful and cheap (but polluting) fossil fuel coal. Iron production is still a major contributor to greenhouse gas emissions, along with steel, cement, paper and chemical manufacturing.


Reproducible: Movie Critique

If time allows, watch one or more movies about climate change. Three of the most well-known are "An Inconvenient Truth" (running time: 100 min.), "Cool It" (running time: 89 min.), and "The 11th Hour" (running time: 91 min.). Make copies of the reproducible to distribute ahead of time so students are prepared to watch the film(s) with a critical eye. Have students complete the worksheet independently. Or have students pair up to write and stage a mock thumbs-up/thumbs-down film critic program. If students watch more than one movie, they can compare and contrast the messages. Offer students an opportunity to informally debate their choice of movie.

Special note: The following information may help you determine if the suggested films are appropriate for your students. It is recommended you view the films ahead of time.

"An Inconvenient Truth":

  • Is rated PG.
  • Contains one very vague reference to drinking alcohol.

"Cool It":

  • Is rated PG.
  • Contains one mild profanity.
  • Contains a brief gory scene involving polar bears.

"The 11th Hour":

  • Is rated PG.
  • Contains one profanity, used casually by an interviewee.
  • Makes several passing references to evolution.
  • Is prefaced by a preview of "Darfur Now," which contains disturbing images that may impact sensitive students. It is recommended you cue up to "The 11th Hour" beforehand.


Independent Research:


  • Using a class email address, sign up for a search engine's "alerts" service on the topic of climate change. Divide students into five groups and assign each a day a week to investigate the emailed alerts. Provide a couple of minutes each day to share important updates with the larger group. Remind students that websites with domain names of .edu or .gov are often safer and more reliable sources of information.
  • Has your region's hardiness zone changed? The Arbor Day Foundation's website reveals recent changes.
  • Using the NOAA's website, invite students to look specifically at their own state's and/or nearest city's temperature and precipitation data since 1900. Is there a pattern of below- or above-normal temperatures or precipitation? The data may reveal cycles of cold and warm years, wet and dry years. If time allows, ask students to plot the data on a graph. Can they draw any conclusions about their state's or nearest city's climate over the past century?
  • What is your state bird? How has its population or migration pattern changed, if at all? What theories, if any, are given to explain this change?
  • Pick one piece of climate change evidence. What reasons - aside from anthropogenic ones - could be given to explain it?
  • Is your state showing signs of climate change? If so, what actions, if any, are being taken at the state level? The local level? (Are there upcoming events in which the group can participate?)

Is anthropogenic global warming really occurring, or are we witnessing the effects of inevitable climate change? Time will tell. All changes, including future changes to climate, force species to adapt or face extinction. A different approach to the climate change issue is to focus on the effect the observed changes are having or could have on humans and take necessary steps. Lesson 2 discusses the impact future environmental changes could have on humans.​ ​