Multiannual changes in atmospheric column transparency based on measurements of direct solar radiation allow us to assess various tendencies in climatic changes. Variability of the atmospheric integral (broadband) transparency coefficient, calculated according to the Bouguer‐Lambert law and transformed to a solar elevation of 30°, is used for two Russian locations, Pavlovsk and Moscow, one Ukrainian location, Feodosiya, and three Estonian locations, Tartu, Tõravere, and Tiirikoja, covering together a 102‐year period, 1906–2007. The comparison of time series revealed significant parallelism. Multiannual trends demonstrate decrease in transparency during the postwar period until 1983/1984. The trend ends with a steep decline of transparency after a series of four volcanic eruptions of Soufriere (1979), Saint Helens (1980), Alaid (1981), and El Chichón (1982). From 1984/1985 to 1990 the atmosphere remarkably restored its clarity, which almost reached again the level of the 1960s. Following the eruption of Mount Pinatubo (June 1991), there was the most significant reduction in column transparency of the postwar period. However, from the end of 1990s, the atmosphere in all considered locations is characterized with high values of transparency. The clearing of the atmosphere (from 1993) evidently indicates a decrease in the content of aerosol particles and, besides the decline of volcanic activity, may therefore be also traced to environmentally oriented changes in technology (pollution prevention), to general industrial and agricultural decline in the territory of the former USSR and Eastern Europe after deep political changes in 1991, and in part to migration of some industries out of Europe.

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The field research reported here contributes to the documentation on the effect of stratospheric aerosols produced by the 1991 eruption of Mount Pinatubo. Using ground‐based data obtained at 2 radiometric stations, located at very different latitudes (Estonia and Spain), we have studied the evolution of the Pinatubo eruption effects. Following the eruption of Mount Pinatubo there is a significant reduction in direct solar radiation, of about 10% in Almeria (Spain) and 7% in Tiirikoja (Estonia). The maximum reduction, of about 15% and 9% respectively, is measured during the 1991‐1992 winter. The aerosol optical depth in Almeria presents, aside from the seasonal dependence, evident influences due to the volcanic aerosol cloud. We have tried to isolate this last effect. As a result, we have found that the 1991/1992 winter presented the maximum volcanic effects, with a decay along 1992 and a recovery in the 1992/1993 winter. These results are in agreement with more sophisticated studies of the aerosol cloud effects. By the 1993‐1994 winter, our analysis shows evidence of a recovery of pre‐eruption conditions confirmed by the aerosol optical depth behaviour during 1994. The analysis of Tiirikoja data set using an atmospheric integral transparency coefficient leads to similar results. The volcanic aerosol effect shows an exponential decay in both locations estimated at 8.6 ± 1.9 months for Almeria and 8.9 ± 3.5 months for Tiirikoja.