Title : Solar influence on winter severity in central Europe

The last two winters in central Europe were unusually cold in comparison to the years before. Meteorological data, mainly from the last 50 years, and modelling studies have suggested that both solar activity and El Niño strength may influence such central European winter coldness. To investigate the mechanisms behind this in a statistically robust way and to test which of the two factors was more important during the last 230 years back into the Little Ice Age, we use historical reports of freezing of the river Rhine. The historical data show that 10 of the 14 freeze years occurred close to sunspot minima and only one during a year of moderate El Niño. This solar influence is underpinned by corresponding atmospheric circulation anomalies in reanalysis data covering the period 1871 to 2008. Accordingly, weak solar activity is empirically related to extremely cold winter conditions in Europe also on such long time scales. This relationship still holds today, however the average winter temperatures have been rising during the last decades. Main text: The last two winters in central Europe were relatively cold [Cattiaux et al., 2010; Guirguis et al., 2011], major rivers like the Rhine were near to freezing, and smaller rivers froze down to the riverbed. Synoptic analyses of these two winters have shown that the cold temperatures in Europe were caused by anomalous atmospheric circulation patterns [Cattiaux et al., 2010; Guirguis et al., 2011], in particular the persistent negative phase of the Arctic Oscillation (AO) and the North Atlantic Oscillation (NAO). This negative NAO phase implies a reduced pressure gradient between