The underlying premise of our paper (McCreadie and Men- vielle, 2010, hereafter referred to as MM2010) and the corri- gendum (McCreadie and Menvielle, 2011, hereafter referred to as Corrigendum) was stated in the Abstract as “What is in doubt is the methodology of the derivation of the index by different groups. The Polar Cap index (PC: PCN, north- ern; PCS, southern) described in Troshichev et al. (2006) and Stauning et al. (2006), both termed the “unified PC index”, and the PCN index routinely derived at DMI are inspected using only available published literature.”. What we mean by “only available published literature” is peer reviewed pa- pers, PhD theses and governmental scientific reports. We showed that the derivation procedures for all three PC indices are different. We argue that the term “unified” cannot be used because the value of the PC index depends upon the chosen derivation procedure. In order to avoid having too long a pa- per we decided not to reproduce developments whenever we found it not necessary in the line of the objective of the paper. We are aware that the choices we made in this respect may be challenged. We should stress the fact that our objective was to make a critical analysis of the differences between the methods and of the points that are not fully described in the litera- ture in order that these points will be addressed in future dis- courses. Our paper is not a critical analysis of the methods. We should also stress the fact that our main objective was not to provide an extensive description of the consequences of the errors that have occurred in the course of the PC index development, but to make clear the differences between the various derivative schemes that have been proposed in order to give the basis for the discussion on a “unified PC index”. In this perspective, we don’t think that a change of institute is an important development in the methodology of the index derivation.