Аннотация:The effect of solar activity and variability on climatic processes during the last 300 years has been studied by analyzing the tree-ring growth at the northern timber line at Kola Peninsula (Russia) and in Scandinavia (Finnish Lapland). It has been shown that there is a good correlation between the solar activity periodicity (22 and 90 years) and cyclicity of climatic processes whose indicator is the tree-ring growth. The tree-ring growth is also the evidence of variability in climatic processes with periods of about 33 and 18 years. Climatic cyclicity with a period of about 35 years is known as the Bruckner cycle. In the paper the physical interpretation of generation of the climatic Bruckner cycle as resulting from the nonlinear effect of solar activity on atmospheric conditions is given.