Radiocarbon calibration with tree rings (1960s-1970s)
Hans Suess and others used bristlecone pine tree rings to show that radiocarbon dates needed calibration. The tree rings provided known-age samples that revealed how atmospheric carbon-14 levels had varied over time.
The first calibration curves were created, correcting radiocarbon dates.
Calibration became standard practice, and the IntCal curve is now updated regularly.
Like the Vesuvius benchmark, tree-ring calibration used known-age materials to improve a dating method's accuracy.
