The main objective is to establish a scientific basis for the detection of the earliest signs of ozone recovery due to Montreal protocol and its amendments. To achieve this we will select the best long-term ozone and meteorological data sets available (by ECMWF and NCEP). Ozone data will be studied by using advanced multiple regression methods developed in this project. Meteorological data would allow to determine the dynamical changes and trends and assess their role in re-distribution of stratospheric ozone in recent decades and in order to force the Chemical Transport Models to assess the relative roles of chemistry and transport in ozone changes. Finally, the synthesis of the key objectives will improve the attribution of observed ozone changes to anthropogenic influences and to the variations in a natural atmosphere.