abstract: The article's goal is to assess the rate of acidification of the Black sea upper layer in XX century using historical data since 1924. It is shown that statistically significant century-scale acidification cannot be extracted, while decadal-scale reduction of pH has been really observing in 1960's and between 1980 and 2000 in spite of high noise level and intense interannual pH variability. The rate of acidification for these periods reached 0.4 (0.2) pH units per decade at the surface (10 m dep
journal: Turkish Journal of Fisheries and Aquatic Sciences