Carbon Dating - Dendrochronology
As we've already seen, in order for Carbon dating to work we need to know what the C-12 to C-14 ratio was at the time of a specimen's death. If the ratio has fluctuated throughout the unobservable past (and we can be sure that it has), how can we determine what the ratio was during the lifetime of a specimen that lived and died before we first began measuring the ratio?
Advocates of the Carbon dating method have turned to "Dendrochronology" (a.k.a. tree-ring dating) to calibrate their timescale (that is, to adjust it to compensate for the C-12 to C-14 ratio fluctuations). By carbon dating a piece of wood which has also been dated by counting its annual tree-rings, scientists can create a table by which they can convert the questionable Carbon-14 years into true calendar years. This is how it works: scientists begin with a living tree or dead wood specimen which can be accurately dated by some reliable means. Then they look for pieces of dead wood which are older than the specimen which they started with and whose tree-ring patterns match up with and overlap those of the first specimen (tree-rings can vary greatly in width due to environmental factors and thus produce a pattern by which we can match specimens which grew in the same environment). Scientists then look for more pieces of dead wood to match and overlap the second specimen and on and on. And finally, they count all of the tree-rings, using the matching patterns to connect all the pieces, and they determine the age of the oldest piece of wood. This is called a "long chronology." By dating the oldest piece of wood using the Carbon dating method and comparing the two dates, scientists can make the necessary adjustments to their calculations.
Unfortunately, this method of calibrating Carbon dating by using tree-ring dating is itself flawed. Dr Walt Brown explains, "…links are established based on the judgment of a tree-ring specialist. Sometimes 'missing' rings are added.1 …Standard statistical techniques could establish how well the dozen supposedly overlapping tree-ring sequences fit. However, tree ring specialists have refused to subject their judgments to these statistical tests and would not release their data so others can do these statistical tests" (Walt Brown, In the Beginning, 2001, p. 246; emphasis in the original). This refusal to submit their work to close scrutiny raises a reasonable concern, especially in light of the apparent circular reasoning employed by the researchers. "Wood specimens considered for 'long chronologies' are first radiocarbon dated. If the date is old enough (perhaps by an erroneous reading), tree-ring specialists look at ring thicknesses for a way to extend the 'long chronology'. This chronology is then used to assure the public that radiocarbon dating has been calibrated by a continuous sequence of tree rings. [This practice is also described by Henry N. Michael and Elizabeth K. Ralph, "Quickee" 14C Dates, Radiocarbon, Vol. 23 No. 1, 1981, pp. 165-166]." (Brown, ibid, p. 246; See also Gerald E. Aardsma, "Myths Regarding Radiocarbon Dating," Impact, No. 189, March 1989.)
Carbon Dating - What Do The Experts Think?
Robert Lee summed up the reasons behind the controversy over the Carbon dating method in his article "Radiocarbon, Ages in Error," published in the Anthropological Journal of Canada: "The troubles of the radiocarbon dating method are undeniably deep and serious. Despite 35 years of technical refinement and better understanding, the underlying assumptions have been strongly challenged, and warnings are out that radiocarbon may soon find itself in a crisis situation. Continuing use of the method depends on a 'fix-it-as-we-go' approach, allowing for contamination here, fractionation here, and calibration whenever possible. It should be no surprise, then, that fully half of the dates are rejected. The wonder is, surely, that the remaining half come to be accepted. …No matter how 'useful' it is, though, the radiocarbon method is still not capable of yielding accurate and reliable results. There are gross discrepancies, the chronology is uneven and relative, and the accepted dates are actually selected dates" (Robert E. Lee, "Radiocarbon, Ages in Error," Anthropological Journal of Canada, Vol. 19, No.3, 1981, pp. 9, 29).