Add sub-categories for novel-CDR variables by method

definitions/variable/variables.yaml

@@ -204,6 +204,12 @@
     unit: Gt CO2/yr
     note: For statistical indicators, the scenario-name column in the IAMC format should
       refer to the scenario ensemble or selection criteria of scenarios
+- Carbon Removal|Novel|{Novel CDR Method}:
+    description: Carbon removal using {Novel CDR Method}
+    unit: Gt CO2/yr
+- Carbon Removal|Novel|Other:
+    description: Carbon removal using other novel methods
+    unit: Gt CO2/yr
 - Carbon Removal|Conventional:
     description: Carbon removal using conventional methods (on land), excluding shifting
       cultivation
@@ -214,6 +220,7 @@
     unit: Gt CO2/yr
     note: For statistical indicators, the scenario-name column in the IAMC format should
       refer to the scenario ensemble or selection criteria of scenarios
+
 - AR6 Climate Diagnostics|Infilled|Emissions|CO2 [{Percentile}]:
     description: Carbon dioxide (CO2) emissions after "infilling" during the AR6 climate
       diagnostics, given as the {Percentile} of a scenario ensemble