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CESM1.1: CLM affects all WACCM compsets with co2_ppmv=0.00001

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CESM1.1: CLM affects all WACCM compsets with co2_ppmv=0.00001

Bugzilla report:



(COMPSETS - 2012-12-27) CRITICAL PROBLEM with the following (primarily
transient CO2) component sets:

All B_RCP* component sets
All B_1850-2000* component sets
All F_AMIP* component sets
All B_*BPRP* and B_*BDRD* component sets
All B_1850_*WACCM* component sets

The -co2_type flag in the CLM namelist is not set correctly and will result in
an invalid value of co2_ppmv being received by CLM.

BUG FIX for CESM1.1:
In your $CASEROOT/Buildconf/clm.buildnml.csh (and only there) modify the
following line


-glc_nec $GLC_NEC -co2_ppmv $CCSM_CO2_PPMV -co2_type $CLM_CO2_TYPE\


-glc_nec $GLC_NEC -co2_ppmv $CCSM_CO2_PPMV \

This climate-changing bug was introduced to CESM1.1 in beta tag cesm1_1_beta18, and is not present in earlier betas or CESM1.0. It is addressed in the first 1.2 beta, and will also be addressed in the CESM1.1.1 minor update.

The above notice may not cover all affected WACCM compsets. To be sure that you are not affected, either:

1) Check to ensure that the "lnd_in" namelist does not have co2_type="constant" and co2_ppmv << 1.


2) Simply implement the above fix before running the model, regardless of which compset you are using, as it is always safe to do so.

Sean Patrick Santos

CESM Software Engineering Group

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