CMIP7 CO2 concentrations for I case

[wwieder]

New CMIP7 files with atmospheric CO2 data are available here /glade/campaign/cesm/cesmdata/input4MIPs_raw/input4MIPs/CMIP7/CMIP/CR/CR-CMIP-1-0-0/atmos/

It would be good to use these consistently with what CAM is using for CESM3

Most similar to our current annual, global file would be

• .../yr/co2/gm/v20250228/co2_input4MIPs_GHGConcentrations_CMIP_CR-CMIP-1-0-0_gm_1750-2022.nc
• I'd upvote this option for simplicity

But there are examples with monthly concentrations:

• globally /mon/co2/gm/v20250228/co2_input4MIPs_GHGConcentrations_CMIP_CR-CMIP-1-0-0_gm_175001-202212.nc
• in 2 lat bands mon/co2/gr1z/v20250228/co2_input4MIPs_GHGConcentrations_CMIP_CR-CMIP-1-0-0_gr1z_175001-202212.nc
• in 12 lat bands mon/co2/gnz/v20250228/co2_input4MIPs_GHGConcentrations_CMIP_CR-CMIP-1-0-0_gnz_175001-202212.nc

Issues in cdeps:
ESCOMP/CDEPS#352
ESCOMP/CDEPS#378

PRs:

• cdeps PR b4b: Introduce separate cmip6 and cmip7 co2 stream files keeping cmip6 as default CDEPS#375 will require a CTSM PR updating .gitmodules in b4b-dev
• Follow with an answer-changing pair of PRs (cdeps + CTSM) when ready to make the cmip7 co2 file the default

[wwieder]

A few additional notes on the CMIP6 files that are currently being used:

• In concentration driven B-cases it looks like CO2 is coming from this file, with "diagnostic CO2 at the lowest model level to be sent from the atmosphere to the land and ocean".   I'm assuming something similar is done for F-cases? *NOTE, this file seems to have latitudinal variation and has units of mol fraction (mol/mol).  It was generated by Doug Kinnison, Simone and Mike Mills
  /glade/campaign/cesm/cesmdata/inputdata/atm/waccm/lb/LBC_17500116-20150116_CMIP6_0p5degLat_c180905.nc

• In I-cases, the CO2 time series is coming from datm, as Cecile notes, specifically the files below. I'm assuming that G-cases use something similar?  NOTE this file does not have latitudinal variation has units of PPM. It was generated by Mike Mills  /glade/campaign/cesm/cesmdata/inputdata/atm/datm7/CO2/fco2_datm_global_simyr_1750-2014_CMIP6_c180929.nc

This is slightly more complicated than I'd expected, suggesting we need a bit of coordination across the CESM project, @briandobbins, @cecilehannay, @klindsay28?

[ekluzek]

In talking about this in CSEG we identified @mnlevy1981 as the contact for Ocean. For Ocean only MARBL uses it. He was going to ask Keith Lindsey about it. CICE doesn't use CO2. So it's @mnlevy1981 and I to work on this.

We also want to make sure we are using the same data as CAM but we probably need some reformatting for streams.

I did have a NCL script that did this reformatting for CMIP6.

[ekluzek]

There's a repository here to put scripts to process CMIP7 datasets.

https://github.com/NCAR/CMIP7_inputdata_processing