diff --git a/components/data_comps/datm/cime_config/namelist_definition_datm.xml b/components/data_comps/datm/cime_config/namelist_definition_datm.xml
index bd30c536205c..f5b666c66521 100644
--- a/components/data_comps/datm/cime_config/namelist_definition_datm.xml
+++ b/components/data_comps/datm/cime_config/namelist_definition_datm.xml
@@ -1944,6 +1944,7 @@
            steps, which is undesirable unless we truly want linear interpolation
            between multiple input values -->
       <value stream="topo.observed">lower</value>
+      <value stream="CORE2_IAF.GISS.SWDN">coszen</value>
     </values>
   </entry>