Now if the magnetic field several thousand years ago was indeed many times stronger than it is today, there would have been less cosmic radiation entering the atmosphere back then and less C would have been produced. In years of severe drought, a bristlecone pine may fail to grow a complete ring all the way around its perimeter; we may find the ring if we bore into the tree from one angle, but not from another. These scrolls are of great significance in the study of Biblical texts because many of them contain the earliest known version of books of the Hebrew bible. Other materials can present the same problem: Now researchers could accurately calculate the age of any object made of organic materials by observing how much of a certain form of carbon remained, and then calculating backwards to determine when the plant or animal that the material came from had died.
Other species of trees corroborate the work that Ferguson did with bristlecone pines.
Facts about radiocarbon dating !
When we know the age of a sample through archaeology or historical sources, the C method as corrected by bristlecone pines agrees with the age within the known margin of error. Without rather special developmental work, it is not generally practicable to measure ages in excess of about twenty thousand years, because the radioactivity of the carbon becomes so slight that it is difficult to get an accurate measurement above background radiation. The answer changes based on the assumptions. Unfortunately, we aren't able to reliably date artifacts beyond several thousand years. Before this can be done, the sample must be treated to remove any contamination and any unwanted constituents.