A tree's growth rate changes in a predictable pattern throughout the year in response to seasonal climate changes, resulting in visible growth rings.
Although it is less accurate, the Libby half-life was retained to avoid inconsistencies or errors when comparing carbon-14 test results that were produced before and after the Cambridge half-life was derived.
This was difficult at the time due to a lack of sufficiently long master dating chronology and access to suitable structures.
Not until 1998 was a Boston area master dating chronology developed.
The university holds some information about tree rings (which is important in climate studies and in archaeology).
Following discusses my attempt to obtain that information, using the Act.