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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A comprehensive investigation on the performance of aerosol optical depth at 500 nm (AOD500) predictions using broadband physical and statistical models is detailed here. Seven simple models and one more complicated model were selected. A special database with more than 26 000 broadband (direct solar beam) and spectral (AODλ) instantaneous observations at clear solar disc during 10 years (2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010)(2011) at Tõravere (Estonia) was compiled for the intercomparison. The database allows analysing the variability and climatological behaviour of several column parameters: coefficient of broadband transparency, precipitable water, AOD500, and the Ångström wavelength exponent (α). A statistical AOD500 model is finally recommended. It uses only two input parameters: coefficient of column broadband transparency and precipitable water. Two models from the set enabled variation of Ångström α. However, consideration of a priori known instantaneous α values did not improve predictions.