Graven et al. (2020)
Also: Graven et al. 2020
Changes to Carbon Isotopes in Atmospheric CO2 Over the Industrial Era and Into the Future
Graven H., Keeling R.F., Rogelj, J., 2020, Changes to Carbon Isotopes in Atmospheric CO2 Over the Industrial Era and Into the Future, Global Biogeochemical Cycles, 34. Link to article.
http://dx.doi.org/10.1029/2019GB006170
References
All IPCC definitions taken from Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Annex I, Glossary, pp. 941-954. Cambridge University Press.