So we wondered whether the radiocarbon levels relevant to dating organic material might also vary for different areas and whether this might affect archaeological dating." The authors measured a series of carbon-14 ages in southern Jordan tree rings, with established calendar dates between 16 A. They found that contemporary plant material growing in the southern Levant shows an average offset in radiocarbon age of about 19 years compared the current Northern Hemisphere standard calibration curve.
"We know from atmospheric measurements over the last 50 years that radiocarbon levels vary through the year, and we also know that plants typically grow at different times in different parts of the Northern Hemisphere.
The other method is “Relative Dating” which gives an order of events without giving an exact age (1): typically artefact typology or the study of the sequence of the evolution of fossils.
There are three carbon isotopes that occur as part of the Earth's natural processes; these are carbon-12, carbon-13 and carbon-14.
Archaeologist Sturt Manning and colleagues have revealed variations in the radiocarbon cycle at certain periods of time, affecting frequently cited standards used in archaeological and historical research relevant to the southern Levant region, which includes Israel, southern Jordan and Egypt.
These variations, or offsets, of up to 20 years in the calibration of precise radiocarbon dating could be related to climatic conditions.