Chapter 10 takes a closer look at the “clocks” (tree rings, ice cores, ocean and lake sediment), historical accounts, and agricultural production documents historians and climate scientists use to track climate in the past. At the American Museum of Natural History in New York City, there is a 16-foot-diameter slab taken from a 1,400-year-old California Giant Sequoia tree. Every tree ring represents one year of growth, and the widths of the rings signal rainfall in the area where they were growing.