Teacher's Guide
Global change is a relatively new area of scientific study using research from many disciplines to determine how Earth systems change, and to assess the influence of human activity on these changes. The Global Change section of the Learning Web consists of an introduction and five activities. In teaching these activities, four themes are important: time, change, cycles, and Earth as home.
The Introduction to Global Change invites students to think about the Earth as a whole and to respect its fragility. The images presented show visible global change.
All poster text and images for the online edition of Global Change are available in PDF format. To view and print the PDF version, you must obtain and install the Acrobat® Reader,, available at no charge from Adobe Systems.
The front of the poster uses metaphor to invite students to think about the Earth as a whole and to respect its fragility. The images presented show visible global change.
The tree-ring image can be used in the "Logs of Straw" activity. Have the students assume the tree was cut down in 1992. Have them calculate the age of the tree and measure the rings to see which years had favorable climate conditions and which had unfavorable conditions.
The Keeling curve relates to the activity, "Where Land, Air, and Water Meet (Change and Cycles)."It shows students how data can be visualized to detect patterns: both the upward trend in the atmospheric concentration of carbon dioxide, and cyclical fluctuations during the growing season.
The greenness maps depict the vigor of vegetation and allow scientists to see how vegetation changes over a growing season and from year to year. Because plants remove carbon dioxide from the atmosphere, such maps may be useful for describing how gases are transferred between the biosphere and the atmosphere.
In the final activity, "An Island Home," (Earth as Home) students can be asked: What happens to an ecosystem when much of the vegetation is removed? Satellite images such as those from the Brazilian rainforest, show human alteration of the landscape. How could the destruction of the rain forest affect the global environment?
Each of the three activities ( "Logs of Straw: Dendrochronology," "Where Land, Air and Water Meet," and "An Island Home") includes background material, an experiment, suggestions for further reading, and extension. Activities can be presented in any order, but "An Island Home" should be used as a summary.
Time
Looking back over the millions of years of the Earth's history, scientists have found evidence of times when climates were very different from today's. Scientists know from fossil records that certain pine trees growing today in Nova Scotia, Canada, once grew more than 1,500 miles farther north on an island near the Arctic Circle. Students will work with simulated tree rings to discover how records of natural phenomena are used to reconstruct past climates
Change
One demonstrable variation in Earth's atmosphere has been the increase in concentration of carbon dioxide (CO,) gas during the past century. "Where Land, Air, and Water Meet" introduces students to measurement in parts per million and concentration. This activity can lead to a discussion of the composition of the atmosphere and of how solar radiation, vegetation, and human activity could influence global warming.
Cycles
Many natural phenomena vary on a regular or periodic basis. An example of this is the changing seasons. Some of the images on the back of the poster demonstrate natural cycles. The concentration of CO, in the atmosphere fluctuates regularly with the seasons. Temperature records reveal a history of thermal cycles in the Earth's climate. Students should be asked to consider cycles and to discuss how cyclical change can be distinguished from change that moves in only one direction.
The Earth as Home
"An Island Home" is an open-ended activity in which students consider how altering part of an ecosystem can cause changes to other parts of the system. This activity uses concepts developed in the other activities to help students look on the Earth as home, and encourage responsible stewardship.
The following books and articles are recommended for more information about global environmental change issues:
de Blij, H.J., editor, 1 988, Earth '88-Changing geographic perspectives: Washington, D.C., National Geographic Society, 392 p.
Jastrow, W., Nierenberg, W., and Seitz, F., 1990, Scientific perspectives on the greenhouse problem Ottawa, Illinois, Jameson Books, 250 p.
Levenson, Thomas, 1989, ice time: New York Harper and Row, 229 p.
Lins, H.F., Sundquist, E.T., and Ager, T.A., 1988, Information on selected climate and climate change issues: U.S. Geological Survey, Open-File Report 88-718, 26 p.
Lovelock, J.E., 1979, Gaia-A new look at life on Earth: Oxford, Oxford University Press, 157 p.
Revelle, Roger, 1982, Carbon dioxide and world climate: Scientific American, v. 247, no. 2, p. 35-43.
Schneider, Stephen H., 1989, Global warming-Are we entering the greenhouse century?: San Francisco, Sierra Club Books, 317 p.
Scientific American, 1989, Managing planet Earth: Scientific American, v. 261, no. 3, p. 47-190.
Stevens, P.R., and Kelley, K.W., 1992, Embracing Earth: San Francisco, Chronicle Books, 176 p.
Weiner, Jonathan, 1968, Planet Earth: New York, Bantam, 370 p.
Zaburunov, Steven A., 1992, As the world breathes-The carbon dioxide cycle: Earth, v.1, no.1, pp. 26-33.
Technical assistance from the following scientists is greatly appreciated: Keith C. Clarke, Hunter College, New York; Richard. S. Williams, Jr., U.S. Geological Survey (USGS), Woods Hole, Massachusetts; and Michael D. Carr, John A. Kelmelis, David A. Kirtland, Harry F. Lins, Robert M. Hirsch, Richard Z. Poore, and Thomas M. Yanosky, USGS, Reston, Virginia.
For information on other USGS products and services, call 1-888-ASK-USGS, use the Ask.USGS fax service, which is available 24 hours a day at 703-648-4888, or visit the general interest publications Web site on mapping, geography, and related topics at http://mac.usgs.gov/mac/isb/pubs/pubslists/index.html .
Please visit the USGS home page at http://www.usgs.gov/.
PDF format reproduces the look of the printed publication. To view and print the PDF version, you must obtain and install the Acrobat® Reader, available at no charge from Adobe Systems. PDF files tend to be of relatively large size and downloading such files from the Internet to your computer via modem may take up to several minutes. Additionally, the quality of illustrations in printed PDF documents will generally be lower than that of the original paper document.
