Radio carbon dating stone tools
These standard calibration curves assume that at any given time radiocarbon levels are similar and stable everywhere across each hemisphere. "We went looking to test the assumption behind the whole field of radiocarbon dating," Manning said.
"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.
"There has been much debate for several decades among scholars arguing for different chronologies sometimes only decades to a century apart -- each with major historical implications. may all be inaccurate since they are using the wrong radiocarbon information," Manning said.
This is how carbon dating works: Carbon is a naturally abundant element found in the atmosphere, in the earth, in the oceans, and in every living creature.
If the ratio is a quarter of what it should be (one in every four trillion) we can assume the creature has been dead for 11,460 year (two half-lives).
Plants and animals naturally incorporate both the abundant C-12 isotope and the much rarer radiocarbon isotope into their tissues in about the same proportions as the two occur in the atmosphere during their lifetimes.
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.
Manning noted that "scholars working on the early Iron Age and Biblical chronology in Jordan and Israel are doing sophisticated projects with radiocarbon age analysis, which argue for very precise findings. But our work indicates that it's arguable their fundamental basis is faulty -- they are using a calibration curve that is not accurate for this region." Applying their results to previously published chronologies, the researchers show how even the relatively small offsets they observe can shift calendar dates by enough to alter ongoing archaeological, historical and paleoclimate debates.
It takes about 5,730 years for half of a sample of radiocarbon to decay back into nitrogen.
It takes another 5,730 for half of the remainder to decay, and then another 5,730 for half of what's left then to decay and so on.