Relation between the true age and that according to carbon-14 dating, from 9,000 to 15,000 years before present, according to measurements in Cariaco (connected points). The straight line is the line of unity. If the atmospheric concentration of carbon-14 had remained fixed, the correspondence would have been perfectly diagonal. Nevertheless, serious deviations are observed. For example, the time of 11 ky according to carbon-14 (on the ordinate), corresponds to a true age of almost 13 ky (on the abscissa).

ref: Hughen K. et al., 1998, Deglacial changes in ocean circulation from an extended radiocarbon calibration, Nature, 391, 65-68

Approximate difference of atmospheric carbon-14 in the last 50,000 years with respect to the present, according to measurements in Cariaco (see detail for the last 10,000 years)

fuente: Hughen K. et al., 2004, 14C Activity and global carbon cycle changes over the past 50,000 years, Science, 303, 202-207

Positive anomaly in the 20th century (decades of 60 and 70) due to the nuclear explosions in the atmosphere.

fuente: Levin I. et al., 2003, A novel approach for independent budgeting of fossil fuel CO2 over Europe by 14CO2 obsevations, Geophysical Research Letters, 1-Dec-2003