| Summary: | The regional climate of the Greater Baltic Area is complex and varies at a multitude of scales in space and time. This thesis contributes to increased understanding of climate change and climate variability in this area focusing on four significant research topics. Droughts have a considerable ecological and socio-economic impact. The occurrence of rainfall is strongly controlled by large-scale atmospheric circulation. The observed summer North Atlantic Oscillation (SNAO) was correlated to a gridded dataset of the self-calibrating Palmer Drought Severity Index. A more positive circulation index is strongly linked to dry conditions over large parts of Southern Fennoscandia and northern Central Europe. Less distinct but still significant is the coupling to wetter conditions in the eastern Mediterranean. Using tree-ring based SNAO and precipitation reconstructions over 550 a, the relationship was investigated back in time in a multicentury perspective. Prior to the instrumental period the coupling is generally less pronounced but holds for distinct periods of drought. A database of up to 121 daily more than century-long instrumental records of precipitation and temperature over Europe was analyzed for trends in climate extremes. Over the 20th century a clear increase of warm extremes and a decreasing trend in cold extremes could be detected. Precipitation extremes became slightly more frequent and precipitation amounts increased, especially during winter. The ongoing warming resulted in a significantly extended thermal growing season in the Greater Baltic Area has extended significantly during the last century. An analysis of 48 long-term daily mean temperature records over this area revealed an overall lengthening of about one week between 1951-2000 mostly contributed by an earlier start in spring. The strongest change was observed at stations adjacent to the Baltic Sea in the South and the weakest in the North East. The 100-year records at Danish stations reveal a maximum shift in start (-22.8 d), end (12.6 d) ...
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