Articles | Volume 10, issue 12
Geosci. Model Dev., 10, 4405–4417, 2017

Special issue: Coupled Model Intercomparison Project Phase 6 (CMIP6) Experimental...

Geosci. Model Dev., 10, 4405–4417, 2017

Model experiment description paper 05 Dec 2017

Model experiment description paper | 05 Dec 2017

Compiled records of carbon isotopes in atmospheric CO2 for historical simulations in CMIP6

Heather Graven1, Colin E. Allison2, David M. Etheridge2, Samuel Hammer3, Ralph F. Keeling4, Ingeborg Levin3, Harro A. J. Meijer5, Mauro Rubino6, Pieter P. Tans7, Cathy M. Trudinger2, Bruce H. Vaughn8, and James W. C. White8 Heather Graven et al.
  • 1Department of Physics, Imperial College London, London, UK
  • 2CSIRO Climate Science Centre, Oceans and Atmosphere, Aspendale, Australia
  • 3Institut für Umweltphysik, Heidelberg University, Heidelberg, Germany
  • 4Scripps Institution of Oceanography, University of California, San Diego, USA
  • 5Centre for Isotope Research, University of Groningen, Groningen, the Netherlands
  • 6Dipartimento di Matematica e Fisica, Università della Campania “Luigi Vanvitelli”, Caserta, Italy
  • 7National Oceanic and Atmospheric Administration, Boulder, USA
  • 8Institute of Arctic and Alpine Research, University of Colorado, Boulder, USA

Abstract. The isotopic composition of carbon (Δ14C and δ13C) in atmospheric CO2 and in oceanic and terrestrial carbon reservoirs is influenced by anthropogenic emissions and by natural carbon exchanges, which can respond to and drive changes in climate. Simulations of 14C and 13C in the ocean and terrestrial components of Earth system models (ESMs) present opportunities for model evaluation and for investigation of carbon cycling, including anthropogenic CO2 emissions and uptake. The use of carbon isotopes in novel evaluation of the ESMs' component ocean and terrestrial biosphere models and in new analyses of historical changes may improve predictions of future changes in the carbon cycle and climate system. We compile existing data to produce records of Δ14C and δ13C in atmospheric CO2 for the historical period 1850–2015. The primary motivation for this compilation is to provide the atmospheric boundary condition for historical simulations in the Coupled Model Intercomparison Project 6 (CMIP6) for models simulating carbon isotopes in the ocean or terrestrial biosphere. The data may also be useful for other carbon cycle modelling activities.

Short summary
Modelling of carbon isotopes 13C and 14C in land and ocean components of Earth system models provides opportunities for new insights and improved understanding of global carbon cycling, and for model evaluation. We compiled existing historical datasets to define the annual mean carbon isotopic composition of atmospheric CO2 for 1850–2015 that can be used in CMIP6 and other modelling activities.