NDC CO2 Price: do not allow co2 price to drop after first target year

main.gms

@@ -1470,7 +1470,7 @@ $setglobal cm_NDC_postTargetDevelopment  constant    !! def = "constant"
 *' *  (zero):                         no minimum carbon price after first NDC target year, i.e. carbon price can decrease to zero after first NDC target year
 *' *  (NPi):                          carbon price cannot fall below carbon price of NPi run as this represent the development of current policies
 *' *  (NonDecreasing):                carbon price cannot decrease after first NDC target year, but can increase or remain constant 
-$setglobal cm_NDC_CO2PriceMinimum  NPi     !! def = "NPi"  !! regexp = zero|NPi|NonDecreasing
+$setglobal cm_NDC_CO2PriceMinimum  NonDecreasing     !! def = "NonDecreasing"  !! regexp = zero|NPi|NonDecreasing
 *' cm_NDC_TargetCheckConv            "choose whether iterations should go on until all NDC emissions targets are fullfilled" [requires 45_carbonprice = NDC]
 *' This setting determines whether compliance with NDC emissions targets should be a criterion for convergence of REMIND. 
 *' *  (on):                         runs only converges if all NDC emissions targets are met within the tolerance defined by cm_NDC_target_DevTol

modules/45_carbonprice/NDC/postsolve.gms

@@ -113,13 +113,17 @@ $elseif.cm_NDC_CO2PriceMinimum "%cm_NDC_CO2PriceMinimum%" == "NPi"
 pm_taxCO2eq(t,regi) = max(  pm_taxCO2eq(t,regi),
                             p45_taxCO2eq_bau(t,regi)  );
 $elseif.cm_NDC_CO2PriceMinimum "%cm_NDC_CO2PriceMinimum%" == "NonDecreasing"
-*** CO2 price cannot decrease after first NDC target year, but can increase or remain constant
+*** As above CO2 price should not fall below NPI run
+pm_taxCO2eq(t,regi) = max(  pm_taxCO2eq(t,regi),
+                            p45_taxCO2eq_bau(t,regi)  );
+*** In addition, CO2 price cannot decrease after first NDC target year, but can increase or remain constant
 loop(regi,
-  loop( t2$( t2.val eq p45_lastNDCyear(regi) ) ,
+  loop( t2$( t2.val eq p45_firstNDCyear(regi) ) ,
     pm_taxCO2eq(t,regi)$(t.val gt t2.val) = max(  pm_taxCO2eq(t,regi), 
                                                   pm_taxCO2eq(t2,regi)  );
   );
 );
+
 $endif.cm_NDC_CO2PriceMinimum
 
 display pm_taxCO2eq;