Indicators: How do Scientists Gather Clues to Climates of the Past? (page 2)

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   1. Trees can also give clues to the weather of the past. The growth rings of trees reveal good and bad growing seasons of past years. Contact your local parks department or a tree-trimming company and request a slice from a tree trunk or limb to be used as part of your science display. Find out more about the growth rings of trees. How do the rings indicate the age of the tree? What differences appear in growth rings during good and bad growing seasons? Display the tree slice, and label rings from these good and bad seasons. Note the age of the tree from which the slice was taken.
   2. Examine the slice and use a pictograph similar to the diagram to represent the good and bad growing seasons during the life of the tree.
   3. If possible, collect different tree slices and compare growth seasons during the same years. Prepare a pictograph of growing seasons for each tree slice.
   4. If one is available, use a measuring instrument called calipers to more accurately determine the width of the growth rings in a cross section of a tree branch or trunk. Compare the width of each ring to the average rainfall and temperature during the year that the ring was formed. Ask a local media meteorologist for information about the average rainfall and temperature in the area where the tree grew.

Check It Out!

Core samples taken in ice layers contain bubbles of air. These tiny trapped air bubbles show which gases were present in the atmosphere when falling snow trapped the air. Find out more about other clues left by nature that reveal information about past climates. How are fossil plants, pollen, and animals used as past climate indicators? How do rocks give clues to the presence and size of glaciers?

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