14 September 2015

CESM1(BGC) Historical Carbon Cycle Characterized

Time series of 20th century (a) 2-m air temperature anomalies and (b) surface net carbon dioxide tracer compared to observations.
Science

Characterize the fidelity of the Community Earth System Model (CESM1) carbon cycle with terrestrial carbon–nitrogen dynamics and an ocean biogeochemical model.

Approach

Two sets of preindustrial-control and 20th century experiments were initialized and forced with prescribed CO2 emissions (PROG) and CO2 mole fractions (PRES).

Impact
  •  CESM1(BGC) configuration used for CMIP5 experiments was introduced and described.
  • Model broadly reproduced observed 20th century carbon cycle, but exhibited notable biases.
  • Model exhibited excessive increase in atmospheric CO2 due to weak land and ocean carbon uptake.
  • Model had a weak seasonal cycle of atmospheric CO2 in the Northern Hemisphere due to seasonal biases in land-to-air CO2 fluxes.
  • Model response of atmospheric CO2 to El Niño Southern Oscillation was too weak.
Contact
Forrest M. Hoffman
Lawrence Berkeley National Laboratory (LBNL)
Acknowledgments

We thank the editor and three anonymous reviewers for helpful comments and suggestions. The CESM project is supported by the National Science Foundation and the Office of Science (BER) of the U.S. Department of Energy. Computing resources were provided by the Climate Simulation Laboratory at NCAR’s Computational and Information Systems Laboratory (CISL), sponsored by the National Science Foundation and other agencies. This research was enabled by CISL compute and storage resources.  SCD acknowledges support from the National Science Foundation (NSF AGS-1048827). This research is supported in part by the U.S. Department of Energy (DOE), Office of Science, Biological and Environmental Research. Oak Ridge National Laboratory is managed by UT-Battelle for DOE under contract DE-AC05-00OR22725.