CESM2 SSP5-8.5 Ensemble

This is a 15 member ensemble of simulations with CESM2 under the SSP5-8.5 forcing scenario from 2015 to 2100. These simulations can be compared with the CESM2 Large Ensemble and provide the opportunity to compare and contrast climate change under a lower forcing scenario. One difference from the official CMIP6 SSP5-8.5 forcing is that slightly modified biomass burning emissions are used at the beginning of the simulation. As is discussed in the CESM2 Large Ensemble reference paper (Rogers et. al. 2021), the second 50 members of the CESM2 Large Ensemble use smoothed biomass burning emissions over the GFED era of the late 20th/early 21st centuries. While the GFED emissions were not prescribed in the SSP scenario, there is a minor effect of the smoothing into the first years of the SSP scenario and these simulations have been branched from historical simulations that used the smoothed biomass burning emissions. As such, this medium ensemble is complementary to the second 50 member of the CESM2 Large Ensemble. Specific information of which member is initialized from which historical member of the CESM2 Large Ensemble is provided below.

We kindly ask that you acknowledge the CVCWG when presenting results based on the CESM2 SSP5-8.5 Ensemble in either oral and written form.

A note about a small discontinuity in biomass burning emissions at the beginning of these simulations:  In the CESM2 large ensemble a smoothed version of the biomass burning emissions were used in the second 50 members to avoid discontinuities in the variance of emissions at the beginning of the GFED satellite era and at the end of the historical period.  In this SSP5-8.5 ensemble, the same approach was used.  The smoothed biomass burning emissions were derived by concatenating the historical and SSP emissions and smoothing with an 11-year running mean filter between the years 1990 and 2020.  Since these SSP5-8.5 simulations are initialized in January 2015 from members of the large ensemble, they are initialized from simulations where the biomass burning emissions were determined by smoothing the concatenation of historical and SSP3-7.0 emissions.  However, the biomass burning emissions that are used in the SSP5-8.5 ensemble were derived from smoothing the concatenation of historical and SSP5-8.5.  In the SSP5-8.5 scenario, there is a small increase in biomass burning emissions between 2015 and 2020 (Figure below, right).  As a result, when the smoothing is performed, the biomass burning emissions at the beginning of 2015 are slightly higher than in the counterpart derived by smoothing the historical into SSP3-7.0 emissions (Figure below, left).  The result is a small jump in the biomass burning emissions at the beginning of these simulations compared to the end of the historical simulations from which they were branched.  This is apparent in a small drop in the globally averaged top of atmosphere shortwave fluxes at the beginning of these simulations. 

Figure comparing smoothed and unsmoothed biomass burning emissions.

Global biomass burning emissions of black carbon for the historical period and the subsequent scenarios.  Left shows the smoothed biomass burning emissions and right shows the unsmoothed emissions.

Project Details

  • Simulation Names:
    • b.e21.BSSP585smbb.f09_g17.CESM2-LE.0XX, XX = 01-15
  • Model Version: CESM2.1.2 Codebase | Documentation
  • Resolution: 0.9x1.25_gx1v6 (CESM nominal 1o grid)
  • Years: 2015-2100
  • Ensemble Size: 15 members
  • Time Frequencies Saved: Monthly, Daily
  • Machine: NCAR:Cheyenne
  • Compset: BSSP585smbb
  • Initial Conditions: Started from the end of: 
    b.e21.BHISTsmbb.f09_g17.LE2-1011.001 (run 001) 
    b.e21.BHISTsmbb.f09_g17.LE2-1031.002 (run 002) 
    b.e21.BHISTsmbb.f09_g17.LE2-1051.003 (run 003) 
    b.e21.BHISTsmbb.f09_g17.LE2-1071.004 (run 004) 
    b.e21.BHISTsmbb.f09_g17.LE2-1091.005 (run 005) 
    b.e21.BHISTsmbb.f09_g17.LE2-1111.006 (run 006) 
    b.e21.BHISTsmbb.f09_g17.LE2-1131.007 (run 007) 
    b.e21.BHISTsmbb.f09_g17.LE2-1151.008 (run 008) 
    b.e21.BHISTsmbb.f09_g17.LE2-1171.009 (run 009) 
    b.e21.BHISTsmbb.f09_g17.LE2-1191.010 (run 010) 
    b.e21.BHISTsmbb.f09_g17.LE2-1251.011 (run 011) 
    b.e21.BHISTsmbb.f09_g17.LE2-1251.012 (run 012) 
    b.e21.BHISTsmbb.f09_g17.LE2-1251.013 (run 013) 
    b.e21.BHISTsmbb.f09_g17.LE2-1251.014 (run 014) 
    b.e21.BHISTsmbb.f09_g17.LE2-1251.015 (run 015) 
  • Additional Notes: CMIP6 time-varying external, natural and anthropogenic forcings from SSP5-8.5 were specified in this ensemble, with the exception that smoothed biomass burning emissions were specified in place of the CMIP6 SSP5-8.5 biomass burning estimates.

Data Acquisition

This data is available on both the NCAR Climate Data Gateway (Web Access) and NCAR's casper system (NCAR Internal).

  • NCAR Internal

    Location on NCAR's campaign store or on the NCAR machine casper:/glade/campaign/cesm/development/cvcwg/cvwg/b.e21.BSSP585smbb.f09_g17.CESM2-LE/

  • Web Access

    The following are step by step directions on how to download this data from the Climate Data Gateway.

    1. Proceed to the CESM2 SSP5-8.5 with Modified Biomass Burning Emissions page.
    2. Scroll to the bottom of that page under Child Datasets, and click on the component and time frequency you are interested in.
    3. The files are organized by variable, listed at the end of each link. Click on the variable you are interested in.
    4. Click on the Download Options button. At this point, if you have not logged into the Climate Data Gateway you can do so now. If you have not registered before, registration is free and quick.
    5. Upon logging in you will see a file listing. Once you have identified a file that you would like to download, click on the check box to the left of the file name. Note that you can select multiple files on this page at once. (However, one cannot select/download multiple files across variables at once.) When you are finished selecting files, scroll to the top (or bottom) of the page and click on the Download Options for Selection box.
    6. Click the Request File Transfer from Archive, and choose whether to use a curl, wget or python script to download your selected data.