Equable climates with mild winters and summers are more likely to maintain snow or ice cover in high latitudes than extreme climates having colder winters and hotter summers. A simplified version of the Milankovitch cycles can be used to develop a model instructors can use in their classes to illustrate the orbital variations producing either equable or extreme climatic conditions. This model, suitable for high school or college use, uses sinusoidal, linear, and hand-drawn representations rather than sophisticated calculations and constructions to convey an understanding of how the earth's orbital variations affect climate. The model encourages students to think about the complex interactions of a few of the climate inputs and to experiment to match the known climate record. An appendix contains diagrams of the earth's rotation and its effects on climate. (Author/LP)