CESM1.2 (CAM5) Idealized Single-forcing simulations

These simulations were run with the NCAR CESM1.2, with CAM5 atmosphere, by Michael P. Erb.  The compset is like B1850C5CN, but with land ice model output so mass-balance terms may be analyzed (but glaciers are non-interactive).  These equilibrium simulations are designed to isolate the climate response to individual past climate forcings.  In each simulation, only one forcing is applied, while all other forcings are set to preindustrial.  Each simulation has been run for 500 years, although the half_CO2 simulation is being run longer because it has not yet approached equilibrium.  The forcings for each simulation are given below.  Forcings not listed are set to preindustial levels.

Land surface: The surface dataset has been altered to remove cities and croplands.  Where croplands were <100%, the other non-zero plant types were simply scaled upward proportionally to sum to 100% in the grid cell.  Where croplands covered cells 100% (this does not apply to many cells), the cells were covered with "C3 grass".

Further details are provided in the papers below:

  • Erb, M. P., Jackson, C.S., Broccoli, A.J. et al., Model evidence for a seasonal bias in Antarctic ice cores. Nat Commun 9, 1361 (2018). https://doi-org/10.1038/s41467-018-03800-0.
  •  Bosmans, JHC, Erb, M.P., Dolan, A.M., et al., Response of the Asian summer monsoons to idealized precession and obliquity forcing in a set of GCMs, Quaternary Sci. Rev., 188, 121-135 (2018). https://doi-org/10.1016/j.quascirev.2018.03.025.

We kindly ask that you reference the appropriate papers and acknowledge the PaleoclimateWG and computing resources from NSF / NCAR CISL when presenting results based on these simulations in either oral or written form. 

Project Details

  • Simulations: 
    • Preindustrial: 
      • b.e12.BG1850C5CN.f19_g16.0ka_0urb.001: obliquity=23.44107o, longitude of perihelion=102.7242, eccentricity=0.01670772, CO2=284.7ppm
    • Obliquity (low and high obliquity of the past 600 ka)
      • b.e12.BG1850C5CN.f19_g16.lo_obliq.001: obliquity=22.079o
      • b.e12.BG1850C5CN.f19_g16.hi_obliq.001: obliquity=24.480o
    • Precession (longitude of the perihelion set to solstices and equinoxes, with increased eccentricity
      • b.e12.BG1850C5CN.f19_g16.0_AEQ.001:    longitude of perihelion=0,   eccentricity=0.0493   (perihelion at NH autumnal equinox)
      • b.e12.BG1850C5CN.f19_g16.90_WSOL.001:  longitude of perihelion=90,  eccentricity=0.0493   (perihelion at NH winter solstice)
      • b.e12.BG1850C5CN.f19_g16.180_VEQ.001:  longitude of perihelion=180, eccentricity=0.0493   (perihelion at NH vernal equinox)
      • b.e12.BG1850C5CN.f19_g16.270_SSOL.001: longitude of perihelion=270, eccentricity=0.0493   (pjerihelion at NH summer solstice)
      • b.e12.BG1850C5CN.f19_g16.ECC_0.001:    eccentricity=0   (no perihelion)
    • Half CO2
      • b.e12.BG1850C5CN.f19_g16.half_CO2.001: CO2=142.35ppm
    • Other (please ignore).
      • b.e12.BG1850C5CN.f19_g16.startup.001: A one month simulation preformed for startup purposes. 
  • Model version: CESM1.2 (CAM5) 
  • Resolution: 1.9x2.5_gx1v6 (finite volume 2o atm grid with nominal 1o ocean and sea ice grids)
  • Years: 500 (all but half_CO2)
  • Ensemble Size: one each forcing
  • Time frequencies Saved: Monthly (all components), daily (ocean only).
  • Machine: NWSC Cheyenne

Data Acquisition

The output (with DOI: https://doi.org/10.5065/D6R2106H) from these simulations is available on the NCAR Climate Data Gateway here.

To obtain output from the Climate Data Gateway (https://www.earthsystemgrid.org/) follow these steps:

  1. Register for a login to the CDG.
  2. Navigate to experiment landing page: https://www.earthsystemgrid.org/dataset/ucar.cgd.ccsm4.PaleoIF.html
  3. Scroll down to Child Datasets, click chosen component and time frequency.
  4. Click chosen ‘Child Dataset’ organized by variable.
  5. Login to CDG to access download options. 
  6. Choose files to download from the list.