In other words, those hoping that uncertainties in radiocarbon dating, say in the assumption of constancy of atmospheric carbon-14 levels, will mean that specimens are really much younger than the measured dates, are in for a big disappointment -- it is now clear that specimens are actually somewhat older than the raw, uncalibrated reckonings.
As mentioned above, young-earth creationist writers have cited various anomalies and potential difficulties with radiocarbon dating, and have used these examples to justify their conclusion that the entire scheme is flawed and unreliable.
Radiocarbon dating, which is also known as carbon-14 dating, is one widely used radiometric dating scheme to determine dates of ancient artifacts.
In discussions of the age of the earth and the antiquity of the human race, creationists often assail perceived weaknesses in radiocarbon dating. Morris, for instance, wrote, "Despite its high popularity, [radiocarbon dating] involves a number of doubtful assumptions, some of which are sufficiently serious to make its results for all ages exceeding about 2000 or 3000 years, in serious need of revision." [Morris2000, pg. Radiocarbon dating is based on the fact that the interaction of cosmic rays from outer space with nitrogen atoms in the atmosphere produces an unstable isotope of carbon, namely radiocarbon.
Various factors affect the accuracy of radiometric measurements.
The amount of cosmic rays resulting from the sun’s activity (with decreasing strength of the earth’s magnetic field) affects the production of carbon-14 (C14).
Since it is chemically indistinguishable from the stable isotopes of carbon (carbon-12 and carbon-13), radiocarbon is taken by plants during photosynthesis and then ingested by animals regularly throughout their lifetimes.
When a plant or animal organism dies, however, the exchange of radiocarbon from the atmosphere and the biosphere stops, and the amount of radiocarbon gradually decreases, with a half-life of approximately 5730 years.
Additional background is available in a well-written Wikipedia article on the topic [Radiocarbon2011], and in Richard Wiens' article [Wiens2002].Comparing these counts with a series of 651 radiocarbon-dated samples spanning this record, they obtained a calibration curve that is very close to the 2009 calibration shown above [Callaway2012]. It should be emphasized that the actual calibrated dates are about 10%-20% older than the raw uncorrected radiocarbon dates that were once used.Compare, for example, the uncorrected line (blue dotted line) with the calibration curve (red curve).The oceans are the largest carbon sinks on the planet, and when they covered 100% of the earth (global flood), instead of todays 70%, carbon levels were arguably different.The half-life of C14 is 5,730 years, meaning half of the C14 will decay in that time and the rest in 50,000 years.C14 levels do not remain constant as assumed and requires calibration as far back as reliable historical data exists - about five thousand years.This correction converts “radiocarbon years” to “calendar years,” but beyond 5,000 years, the correction and resulting ages are left to guess work.Because of this relatively short half-life, radiocarbon is useful for dating items of a relatively recent vintage, as far back as roughly 50,000 years before the present epoch.Radiocarbon dating cannot be used for older specimens, because so little carbon-14 remains in samples that it cannot be reliably measured.For instance, creationist Walt Brown has pointed out inconsistencies in some radiocarbon dates of mammoths -- one part was dated to 40,000 years, another to 26,000 years (and wood surrounding it to 10,000 years), and yet another to between 15,000 and 21,000 years before the present epoch [Brown2001].However, in the scientific results mentioned by Brown, the dates come from different mammoth specimens.