¹⁴C Trends: Going Backwards in Time

Measured ¹⁴C/C in atmospheric CO₂ over 1950-2015 from a compilation[1] and from individual samples over 2014-2021 from sites[2] in the Northern Hemisphere (La Jolla at 32°N and Mauna Loa at 20°N) and the Southern Hemisphere (Samoa at 14°S and South Pole at 90°S). The compilation combines various data sources and is representative of tropical regions[1]. Data are reported with typical normalization and correction[3]. Preliminary data from individual samples are shown for 2014-2021, data are publicly available at https://scrippsco2.ucsd.edu/ after quality control.

Please cite as: Graven, H, R Keeling and X Xu, 2022. Radiocarbon dating: Going back in time. Nature.

Acknowledgments
The Scripps CO₂ program has been supported by a series of grants from U.S. NSF, DOE, NOAA, and NASA, most recently by OPP-1922922, NNX17AE74G, and the Schmidt Futures Program. These 14C measurements were supported by NASA and the Leverhulme Trust.

References

1. Graven, H., et al., Compiled records of carbon isotopes in atmospheric CO2 for historical simulations in CMIP6. Geosci. Model Dev., 2017. 10(12): p. 4405-4417.
2. Graven, H.D., T.P. Guilderson, and R.F. Keeling, Observations of radiocarbon in CO2 at seven global sampling sites in the Scripps flask network: Analysis of spatial gradients and seasonal cycles. J Geophys Res, 2012. 117(D2): p. D02303.
3. Stuiver, M. and H.A. Polach, Discussion: Reporting of 14C Data. Radiocarbon, 1977. 19(3): p. 355-363.