Impacts of climate variability, trends and NAO on 20th century European plant phenology

We provide here a brief overview of the impacts of climate variability and recent climate change on the European plant phenology across the 20th century. Facing recent climate changes, phenology has two major functions. Firstly, it reveals measurable impacts of climate change on nature, which at the same time clearly demonstrate global climate change in people’s backyards. Secondly, long-term phenological data allow the reconstruction of temperature and its variability in the last centuries. The most prominent temperature driven changes in plant phenology are an earlier start of spring in the last three to five decades of, on average, 2.5 days/decade, mainly observed in midlatitudes and higher latitudes of the northern hemisphere. More heterogeneous changes in autumn are not as pronounced as in spring and cannot be linked to climate factors. A marked spatial and temporal variability of spring and summer onset dates and their changes can be mainly attributed to regional and local temperature. In this context, we discuss the temperature responses of the growing season and other phenological phases and their relation to the North Atlantic Oscillation. These results illustrate main feedbacks in biogeochemical cycles and land-surface interactions of the climate system.