<Table> <Tr> <Td> </Td> <Td> This article needs additional citations for verification . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed . (November 2014) (Learn how and when to remove this template message) </Td> </Tr> </Table> <Tr> <Td> </Td> <Td> This article needs additional citations for verification . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed . (November 2014) (Learn how and when to remove this template message) </Td> </Tr> <P> Dendrochronology (or tree - ring dating) is the scientific method of dating tree rings (also called growth rings) to the exact year they were formed in order to analyze atmospheric conditions during different periods in history . Dendrochronology is useful for determining the timing of events and rates of change in the environment (most prominently climate) and also in works of art and architecture, such as old panel paintings on wood, buildings, etc . It is also used in radiocarbon dating to calibrate radiocarbon ages . </P> <P> New growth in trees occurs in a layer of cells near the bark . A tree's growth rate changes in a predictable pattern throughout the year in response to seasonal climate changes, resulting in visible growth rings . Each ring marks a complete cycle of seasons, or one year, in the tree's life . As of 2013, the oldest tree - ring measurements in the Northern Hemisphere are a floating sequence extending from about 12,580 to 13,900 years . Dendrochronology derives from Ancient Greek: δένδρον (dendron), meaning "tree", χρόνος (khronos), meaning "time", and - λογία (- logia), "the study of". </P>

Age of tree by counting the annual ring