Calculating Anomalies By Using Climatology. Python code.
The issue: Drift makes the comparison of the nuclear war run to a climatology not 100% accurate for some variables in the ocean. We test this out with Ocean Heat Content (OHC) variations globally within the first 1000 meters of the water column during nw_cntrl_03 (the control run) and nw_ur_150_07 (150 Tg soot injection). The trend in the control run compared to the change in the nuclear war run is minimal.

Actual OHC during the control run shows evidence of a small amount of drift in global ocean temperatures:

Differences Between Both Methods in the Equatorial Pacific Ocean

Comparison of two anomaly methods for equatorial Pacific temperature anomalies during nw_ur_150_07.

Method 1: nw_ur_150_07 yyyy-mm - nw_cntrl_03 yyyy-mm (crude climatology)
vs.
Method 2: nw_ur_150_07 yyyy-mm - nw_cntrl_03 mm climatology

Comparison of control (nw_cntrl_03) vs nw_ur_150_07 equatorial Pacific temperature anomalies using method 2.