During the last year of POLARCAT, the findings of the international program shall be published in at least one special issue of a major scientific journal (e.g., J. Geophys. Res.). In addition to the specialized papers on various topics, a synthesis paper shall be written that integrates all the POLARCAT findings and highlights what we have learned during IPY. This paper shall have a review character and will put the POLARCAT results into the proper historical perspective.