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How can scientists use tree-ring widths to study past climates?

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temperate softwoods and hardwoods selected to show variations — wood Temperate softwoods (left column) and hardwoods (right column), selected to highlight natural variations in colour and figure: (A) Douglas fir, (B) sugar pine, (C) redwood, (D) white oak, (E) American sycamore, and (F) black cherry. Each image shows (from left to right) transverse, radial, and tangential surfaces. Click on an individual image for an enlarged view.

Scientists use tree-ring widths to study past climates through the field of dendroclimatology. Because many trees produce annual growth rings, the width of these rings serves as a biological record of environmental conditions during the growing season.12

The process works because radial growth is closely tied to the weather conditions of a specific year. In many species, ring width varies in direct proportion to the amount of available precipitation or prevailing temperatures. For instance, a cold spring or a period of drought can significantly decrease the amount of growth, resulting in narrower rings. By measuring these variations and correlating sequences from different trees—including living specimens, dead wood, and ancient structures—scientists can reconstruct climatic trends extending back thousands of years.2134

Beyond simple width, researchers also analyze the thickness and composition of cell walls and the diameter of the lumen to extract more detailed information about past weather patterns. While factors like soil quality and tree age can influence growth, the consistent, climate-sensitive nature of these rings makes them invaluable for understanding historical environmental changes.23