Variations in atmospheric 14C

The article reviews the calibration of the Radiocarbon timescale. The calibration curve reveals variations of the 14C content in nature for the last 50,000 years. These variations yield crucial information on diverse subjects such as calibration into absolute ages of past human and natural events, but also the past strength of the geomagnetic field, solar fluctuations, and reorganizations in the global Carbon cycle. The observations are discussed for four time periods: the Holocene, the Deglaciation, the Middle/Upper Paleolithic and the Anthropogenic era.