Using a consistency factor for detection and attribution of anthropogenic impacts on phenological phases in Germany

1 An important consequence of climate change is the impact on the seasonal 2 cycle of vegetation flora and fauna. Although it is generally understood that 3 anthropogenic mechanisms play a major role in the warming trend of the 4 climate and that the timing of such phases, especially spring timing events, 5 depends largely on the temperature, the link has yet to be quantitatively 6 shown for different kind of areas on a regional scale, due to high intrinsic 7 noise. 8 In this study, an end-to-end analysis to external forcings was carried out, 9 linking the earlier timing of phenological spring timing events to changed 10 climate conditions (increasing temperature) and this change in the environ11 ment to anthropogenic forcing, for the region of interest: Germany. 12 Besides a large ensemble originating from six different General Circulation 13 Models (GCMs), driven with various kinds of forcings, the E-OBS data set 14 was used as observational reference for near-surface air temperature and the 15 PEP725 for phenological observations. The latter contains over 100 differ16 ent phenological phases, from which after quality checking 12 phases are 17 evaluated. 18 To overcome the scale differences, a quantile mapping bias correction ap19 proach was used to downscale the GCM data. The generation of simulated 20 phenological time series was done with a temperature-day-sum model, which 21 had to be calibrated and optimised beforehand. 22 The signal-to-noise ratio was increased by generating samples of 50-year run23 ning trends, which make up the basis for the statistical evaluation. U-values 24 from the Mann-Whitney U-Test represent the foundation, on which the null 25