Removing the chemistry entirely is not possible (and would not give reasonable results), but you can use Specified Chemistry WACCM (SC-WACCM), which runs significantly faster than WACCM with full interactive chemistry. SC-WACCM uses prescribed forcing datasets that were created from a normal WACCM run, so for many purposes it will provide similar results to a full WACCM run.To use SC-WACCM, just create a case using one of the specified chemistry compsets, and configure it as you would a typical WACCM run. CESM 1.0.5 and CESM 1.2.0 both have bugs in the default SC-WACCM settings, and have very few compsets. Therefore I recommend switching to CESM 1.0.6 or CESM 1.2.2, because these offer many more SC-WACCM compsets, and they also have those known bugs fixed.If you use CESM 1.0.6, note that one of the specified chemistry compsets, FWSC, has the bug mentioned here:https://bb.cgd.ucar.edu/cesm106-fwsc-does-not-run-default-namelist