The following article is abstracted from The Biblical Chronologist Volume 5, Number 1. The science of constructing chronologies from tree rings is called dendrochronology. Modern trees are known to produce one growth ring per year. (The idea that ancient trees grew more than one ring per year will be discussed below.) Therefore, by coring a living tree and counting rings from the present backwards, it is possible to determine the year in which each ring grew. The bristlecone pines in the White Mountains of California live to extremely old ages, some in excess of 4,000 years.
The University of Arizona dendrochronology lab sports a (no longer living) specimen which contains over 6,000 rings.
This is accomplished using wood specimens found preserved, for example, in historic buildings, or on the forest floor, or in peat bogs.
The rings in a non-living specimen can be counted to determine the number of years the specimen spans.
But for the specimen to be useful in extending the tree-ring chronology, the absolute calendar age of its rings must be determined.
The annual growth rings vary in thickness each year depending on environmental factors such as rainfall.
We could discuss the details of pattern-matching technique or the probability of error, but there is another, more quantitative way, to determine if the long tree-ring chronologies are accurate or not.
One can use the amount of radiocarbon in the individual tree rings.
Because radiocarbon is everywhere the same in the atmosphere at any given time, tree rings which grew in the same year should have the same amount of radiocarbon.
By matching ring-width patterns in a specimen of known age (starting with living specimens) to ring-width patterns in an older specimen, the proper placement of the older specimen is determined.
Tree-ring chronologies have been extended to 10,000 years before present in this way.
Some critics of dendrochronology suggest that the process of pattern-matching is highly error-prone.
Are the long tree-ring chronologies inaccurate due to the inability of dendrochronologists to accurately match tree-ring patterns?