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Boreal regions are sensitive to modifications in climatic conditions especially when the climate mode is changing fundamentally like in the middle to late Pliocene. This was the time when the N Hemisphere experienced a major cooling which lead into an extended glaciation. The environmental reorganisation apparently coincides with Eurasian orographic reorganisations, which to some extent caused adaptations in the atmospheric circulation. Lake Baikal, in the interior of a large landmass, has been shown to record continuously environmental changes at least for the last 10 Ma. The age models for all sediment cores are based on palaeomagnetic records. The sediments provide the basis for assessing vegetation changes and detritus discharge from the hinterland and allow highlighting the limnological changes for critical time windows. During the late Pliocene climatic oscillations started step-by-step with arid phases and lowered temperature some 3.5 Ma ago. Aridification and growing seasonality was progressing until about 2,6 Ma when Central Siberia, possibly already a key location for the N Hemisphere atmospheric system by this time, has definitely entered into a new mode.
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