Well, they really bark, I think. They tell stories about the Earth's past. Oh, you must mean how tree rings tell us what the weather was like a long time ago. This is Kids' Earth and Sky. Trees can't speak, but they can tell a story about Earth's past.
Some trees grow an extra layer of wood every year as the seasons change.
It grows just inside the bark of a tree. The thickness and appearance of this new wood depends on that year's weather and other conditions. So these extra layers of wood are like clues to the riddle of Earth's weather from long ago. If you cut down a tree, you'd see a series of tree rings nestled inside each other. Each ring is made from the wood that grows every year.