We can only make assumptions about past atmospheric carbon nuclide regimes, which introduces a significant unknown variable.
Even attempts to compensate for the routine misuses of dating results have been misguided. carbon isotope ‘dates’ is misleading, in that it elicits a false sense of security in practitioners.
For instance, the introduction of once fashionable terms such as ‘absolute dates’ and ‘relative dates’, or the use of ‘calibrated’ radiocarbon dates have only provided cures worse than the disease; rather than correcting the problem they tried to conceal it. Reference to a calibration curve proposed for bristlecone pine in some part of California does not compensate for the numerous inherent qualifications of radiocarbon results, it merely compounds interpretational confusion.
Very few methods are known of absolute dating, such as dendrochronology (analysing the annual growth rings of sectioned tree trunks) and counting of annual ice layers (particularly in Greenland and Antarctica).
Another possibility might be the annual luminescence banding in carbonate speleothems (Baker et al. All other methods used in dating yield results that cannot be expressed in calendar years, sidereal time or absolute historical time, irrespective of any ‘calibration’ used.
In the case of radiocarbon, the remnant content of an unstable and thus radioactive isotope of carbon is determined to estimate the time when its decay to nitrogen commenced.