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Since the tree ring counts have reliably dated some specimens of wood all the way back to 6200 BC, one can check out the C-14 dates against the tree-ring-count dates.Admittedly, this old wood comes from trees that have been dead for hundreds of years, but you don't have to have an 8,200-year-old bristlecone pine tree alive today to validly determine that sort of date.In the growth-ring analyses of approximately one thousand trees in the White Mountains, we have, in fact, found no more than three or four occurrences of even incipient multiple growth layers. 840) 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.
As Hurley points out: 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. 108) Cosmic rays form beta radiation all the time; this is the radiation that turns N-14 to C-14 in the first place. If we extrapolate backwards in time with the proper equations, we find that the earlier the historical period, the less C-14 the atmosphere had.
However, the amount of C-14 has not been rising steadily as Cook maintains; instead, it has fluctuated up and down over the past ten thousand years. From radiocarbon dates taken from bristlecone pines.
There are two ways of dating wood from bristlecone pines: one can count rings or one can radiocarbon-date the wood.
Even so, the missing rings are a far more serious problem than any double rings.
Other species of trees corroborate the work that Ferguson did with bristlecone pines.
Question: But don't trees sometimes produce more than one growth ring per year? Answer: If anything, the tree-ring sequence suffers far more from missing rings than from double rings.