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. This activity uses concepts developed in the other activities to help students look on the Earth as home, and encourage responsible stewardship. 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. This teacher packet was originally published and printed in 1993.