4.0 CLIMATE CHANGE
The graphs in Chapter 1 (p. 4 of Global Change and Canadians),
showing the relationship between greenhouse gas concentrations and global temperatures provide a useful tool for thinking about the relationship between the concentrations of these gases and the energy budget of the Earth's atmosphere. Figure 12, p.22, shows the steady increase in atmospheric carbon dioxide since the start of the 18th century which saw the beginnings of the Industrial Era when humans began to use significant amounts of fossil fuels, especially coal, to provide energy. Students reading through Chapter 4 of Global Change and Canadians, should note the relationship between the greenhouse gas concentrations and global temperatures. This will provide an introduction to many of the following activities.
[Sidebar
This activity provides an introduction to the other activities under the Air subsection of the guide.]
4.1 THE GREENHOUSE EFFECT
The "greenhouse effect" refers to the similarity between the Earth's atmosphere and the glass of a greenhouse. To illustrate this place one thermometer inside a covered glass terrarium or aquarium outside on a sunny day. Nearby, place the other thermometer which is outside the enclosure, but otherwise which has the same exposure to the sun. Have students compare the temperatures shown on the two thermometers over time. They will soon notice that the thermometer inside the small "greenhouse" shows a higher reading than does the one in the open air. Why is there a difference in the two thermometer readings?
Have the students look at the diagram on p.19. It shows the major energy relationships in the Earth's atmosphere. Students should think about what will happen to the Earth's energy budget if:
- there were lower amounts of greenhouse gases.
- there were higher amounts of greenhouse gases.
[Sidebar
Polls have noted that the majority of Canadians believe that the primary cause of global warming is the thinning of the ozone layer.
While the greenhouse effect is often treated as a problem, the natural greenhouse effect is crucial for life on earth. The problem is not the greenhouse effect but the rate of change or intensity of it.]
4.2 THE "GOLDILOCKS" PLANET
What makes Earth the "Goldilocks" Planet-"just right" for life? The Earth has two nearby neighbouring planets: Venus and Mars. Venus is nearly the same size as the Earth, and is somewhat closer to the sun. At one time it was thought that Venus might well be very similar to Earth, if a little warmer or more tropical. Today, space probes have shown Venus to be the possible victim of a greenhouse effect gone wild. It has a very dense, acidic atmosphere. The temperature at the surface of Venus is very high and it appears to be without water. Three teams of students could compare the atmospheric composition of the Earth, Mars, and Venus, and describe their surface conditions. Mars and Venus appear to be lifeless.
4.3 GREENHOUSE GRAPHING
The graphs on p.4 of Chapter 1 showing greenhouse gas concentrations and global temperature over time suggest that when greenhouse gases are high in concentration, the Earth's atmosphere has a higher average temperature. Ask students to decide whether or not the graphs on p.4 "prove" that greenhouse gases cause the atmosphere's temperature to rise? What other things might cause such a change in atmospheric temperature?
Invite the students to find out:
- how scientists know the temperature of the ancient atmosphere of the Earth, prior
to humans keeping temperature records;
- how reliable the methods to estimate past atmospheric carbon dioxide
concentrations are considered to be; and
- how computer simulations or models are used to test theories about global
warming and how reliable the models are considered to be as means of making
predictions.
Each team could make a brief presentation showing:
- how the research data are gathered or how the computer model is made
- how reliable the data or models are considered to be
- possible weaknesses in the data or models
4.4 GLOBAL WARMING
Pages 22-23 of Global Change and Canadians list some possible outcomes of global warming. Prior to presenting the list to students and discussing it, ask the students to think about the possible consequences (physical, political, economic, etc.) of an average increase of 2.0o C in the total atmospheric temperature. This does not seem to be a very great change: it is, however, a worldwide average. Some regions might show much greater changes than others because solar energy is not equally distributed on the Earth's surface-why?
[Sidebar
The concern is not the greenhouse effect but the projected increase in intensity or magnitude of the greenhouse effect that has garnered the label global warming. It must be stressed that it is the projected rate of change, not just change, that is of concern.]
4.5 GLOBAL WARMING—A GOOD THING?
Ask the students to consider possible positive benefits of global warming, as well as negatives . The students could create a two column table with one column listing possible positive consequences from global warming and the other negative ones. Remind students that all suggestions are valid during brain-storming.
In developing the table of possible positive and negative consequences of global warming ensure students consider the impact of this sort of global change on all life forms. How did plant and animal populations in North America cope with the last ice age when vast ice sheets covered much of Canada? Speculate as to how these populations might respond to global warming? ( See Appendix 1-Sample Lesson Plans for a detailed description of this activity.)
4.6 THE LITTLE ICE AGE
In recent history the northern hemisphere in particular experienced a long period of very cold temperatures, with cool wet summers and cold, snowy winters. This period is known as the Little Ice Age. Assign a team of students to find out as much as possible about life in this period and the effects this short-term, but important climate change had on human life. The team should prepare a presentation outlining their findings. Is anything known about the causes of the Little Ice Age?
4.7 STRATOSPHERIC OZONE MOLECULES
Have students use plasticine or modelling clay and tooth picks or wooden meat skewers to make models of molecules of oxygen gas and ozone. How do they differ? How are these compounds formed in nature? Was there any ozone before humans? The class could create a display using the models and posters to illustrate the environmental importance of oxygen and of ozone at ground level and in the upper atmosphere
4.8 STRATOSPHERIC OZONE DEPLETION
Plan with the teacher-librarian to organize student research into the extent of known ozone depletion in recent years in the upper atmosphere over the Antarctic and Arctic. Find out:
- Why is there a difference in the degree of ozone depletion over the two poles?
- What are the seasonal variations of ozone depletion over the two poles and in other areas of the atmosphere?
Present the findings on colored maps or overhead projector transparencies.
[Sidebar
There are grounds for confusion when dealing with this subject because of the role that ozone plays in the lower and upper atmosphere. In the lower atmosphere increases in ozone are considered harmful because it is a serious atmospheric pollutant but in the upper atmosphere its abundance is crucial for life. The dual role of ozone should be noted in the display and modelling exercise.]
4.9 OZONE DISPLAY
Create a dislay showing the technologies which are responsible for ozone depletion. Consider CFCs and HCFCs, which were formerly or are now used in various technologies. Try to identify those technologies as well as substitutes for CFCs and HCFCs. Remember supersonic flight!
4.10 Entrevues sur l'ozone
What are the potential results of upper atmosphere ozone depletion? Students can interview some of the following source people:
- a dermatologist regarding the hazards of sun exposure
- a plant scientist regarding crop damage from UV exposure
- a geneticist concerning UV damage to developing larvae
- a local retailer regarding sales of sun screen and hats
- an ecologist regarding predator-prey relationships
[Sidebar
There are grounds for confusion when dealing with this subject because of the role that ozone plays in the lower and upper atmosphere. In the lower atmosphere increases in ozone are considered harmful because it is a serious atmospheric pollutant but in the upper atmosphere its abundance is crucial for life. The dual role of ozone should be noted in the display and modelling exercise.]
4.11 THE MONTREAL PROTOCOL
Students should prepare a presentation on the Montreal Protocol. The class might brainstorm possible topics for inclusion in such a presentation by asking questions after reading the description of the protocol on p.25 of Global Change and Canadians. Some suggestions are:
- define the Montreal Protocol
- list the nations which have signed it; which have not signed it, and why
- provide some alternatives to CFCs and explain why they were not used earlier
- there are different timetables for compliance with the Montreal Protocol for
developed versus developing nations-why?
- what progress has Canada made?
Assign a pair of students to address each question and present their findings to the class or use a method of sharing from cooperative learning techniques.
4.12 AIR MODELS
Students can use drawings or models to illustrate the major components of air pollution, specifically nitrogen and sulphur oxides. How are these compounds produced in the burning of coal, fuel oil, or gasoline? Use models to show how they react with water in the air.
4.13 HOW ACIDIC IS THE RAIN?
Students can test a sample of distilled water for its acidity using pH paper. Set up a large jar on the roof of the school, window ledge of the classroom, or some other spot which is open to the rainfall but where the jar will not be disturbed. After rain water has collected in the jar test the rainfall with pH paper. What is the pH of the rainfall in your area? Test the pH of vinegar, Coke, etc. and compare to the collected rainwater.
4.14 EXHAUST pH
Tape a filter paper or coffee machine filter over the exhaust pipe of a car. Do this when the car is not running and when the exhaust pipe is cool. Also be sure to do it in an open, well ventilated area. When the filter is in place, have the driver start the car and run the engine for 3-5 minutes. Remove the filter after the engine has been turned off and the exhaust pipe has cooled. Spread out the filter and observe any materials trapped by it.
Next fill a large beaker or jar with distilled water. Place a clean filter paper or coffee filter in the water and shake well. Take the pH of the water after the shaking using pH paper. Record the pH reading. Now fill another clean jar or beaker with distilled water and immerse the filter paper removed from the exhaust pipe in the water. Shake well. Then take a pH reading from the water in which the exhaust filter has been shaken. How do the two results compare? What causes the difference?
4.15 WHAT'S IN THE AIR?
Get some small pieces of window glass or ordinary microscope slides. Spread Vaseline in a thin film on the surface of the glass. Place the glass on the classroom window ledge, or on the school roof, preferably where the glass is open to the air but is not directly exposed to rainfall. Leave the Vaseline coated glass exposed for 1-2 days. Bring the glass into the classroom and use a large hand lens or microscope under low power magnification to examine the coated surface. What sorts of things are trapped in the greasy film? Repeat this trial inside the classroom. How does the air in the classroom compare with that outside?
4.16 ALTERNATIVE FUELS
Hydrogen has been proposed as an alternative to fossil fuels. Some auto manufacturers are experimenting with hydrogen-powered cars but they are not commercially available. Battery power has also been proposed as a way to reduce or eliminate air pollution from cars. Have several student teams do research to find out as much as possible about
alternative auto fuels or power sources. The teams should present their findings and try to create a table showing the plus and minus features of the various alternatives. (See Appendix 1-Sample Lesson Plans for a detailed description of this activity.)
4.17 THE UNLEADED STORY
For many years tetraethyl lead was added to gasoline to improve auto engine performance. In much of the developed world this is no longer done. Why was the lead taken out of gasoline? Find out which countries in the world still permit the use of lead in auto fuels-why do they still permit lead additives? What is known about the movement of lead in the ecosystem? Is lead from past years still being transported in the biological system? What consequences has this had for human health? Create a display or group presentation on the results of your inquiry.P>
Invite class discussion around the idea that the lead-in-gasoline case is a good illustration of the need for much better assessment of the potential environmental consequences of new technologies. What did the scientific community know about the possible hazards of adding lead to gas at the time that this was first done?
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