Articles | Volume 9, issue 8
Geosci. Model Dev., 9, 2853–2880, 2016

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

Geosci. Model Dev., 9, 2853–2880, 2016

Model experiment description paper 25 Aug 2016

Model experiment description paper | 25 Aug 2016

C4MIP – The Coupled Climate–Carbon Cycle Model Intercomparison Project: experimental protocol for CMIP6

Chris D. Jones1, Vivek Arora2, Pierre Friedlingstein3, Laurent Bopp4, Victor Brovkin5, John Dunne6, Heather Graven7, Forrest Hoffman8, Tatiana Ilyina5, Jasmin G. John6, Martin Jung9, Michio Kawamiya10, Charlie Koven11, Julia Pongratz5, Thomas Raddatz5, James T. Randerson12, and Sönke Zaehle9 Chris D. Jones et al.
  • 1Met Office Hadley Centre, Exeter, EX1 3PB, UK
  • 2Canadian Centre for Climate Modelling and Analysis, Climate Research Division, Environment and Climate Change, Victoria, Canada
  • 3College of Engineering, Mathematics and Physical Sciences, University of Exeter, Exeter, EX4 4QE, UK
  • 4Laboratoire des Sciences du Climat et de l'Environnement, LSCE/IPSL, CEA-CNRS-UVSQ, Université Paris-Saclay, 91191 Gif-sur-Yvette, France
  • 5Max Planck Institute for Meteorology, Hamburg, Germany
  • 6NOAA/GFDL, Princeton, NJ, USA
  • 7Department of Physics and Grantham Institute, Imperial College London, London, UK
  • 8Oak Ridge National Lab., Oak Ridge, TN, USA
  • 9Biogeochemical Integration Department, Max Planck Institute for Biogeochemistry, 07745 Jena, Germany
  • 10Japan Agency for Marine-Earth Science and Technology, Kanagawa, Japan
  • 11Earth Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
  • 12Department of Earth System Science, University of California, Irvine, CA USA

Abstract. Coordinated experimental design and implementation has become a cornerstone of global climate modelling. Model Intercomparison Projects (MIPs) enable systematic and robust analysis of results across many models, by reducing the influence of ad hoc differences in model set-up or experimental boundary conditions. As it enters its 6th phase, the Coupled Model Intercomparison Project (CMIP6) has grown significantly in scope with the design and documentation of individual simulations delegated to individual climate science communities.

The Coupled Climate–Carbon Cycle Model Intercomparison Project (C4MIP) takes responsibility for design, documentation, and analysis of carbon cycle feedbacks and interactions in climate simulations. These feedbacks are potentially large and play a leading-order contribution in determining the atmospheric composition in response to human emissions of CO2 and in the setting of emissions targets to stabilize climate or avoid dangerous climate change. For over a decade, C4MIP has coordinated coupled climate–carbon cycle simulations, and in this paper we describe the C4MIP simulations that will be formally part of CMIP6. While the climate–carbon cycle community has created this experimental design, the simulations also fit within the wider CMIP activity, conform to some common standards including documentation and diagnostic requests, and are designed to complement the CMIP core experiments known as the Diagnostic, Evaluation and Characterization of Klima (DECK).

C4MIP has three key strands of scientific motivation and the requested simulations are designed to satisfy their needs: (1) pre-industrial and historical simulations (formally part of the common set of CMIP6 experiments) to enable model evaluation, (2) idealized coupled and partially coupled simulations with 1 % per year increases in CO2 to enable diagnosis of feedback strength and its components, (3) future scenario simulations to project how the Earth system will respond to anthropogenic activity over the 21st century and beyond.

This paper documents in detail these simulations, explains their rationale and planned analysis, and describes how to set up and run the simulations. Particular attention is paid to boundary conditions, input data, and requested output diagnostics. It is important that modelling groups participating in C4MIP adhere as closely as possible to this experimental design.

Short summary
How the carbon cycle interacts with climate will affect future climate change and how society plans emissions reductions to achieve climate targets. The Coupled Climate Carbon Cycle Model Intercomparison Project (C4MIP) is an endorsed activity of CMIP6 and aims to quantify these interactions and feedbacks in state-of-the-art climate models. This paper lays out the experimental protocol for modelling groups to follow to contribute to C4MIP. It is a contribution to the CMIP6 GMD Special Issue.