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DANGENDORF ET AL. 
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source for investigating surges and hence storminess. 
For Europe, tide gauges located in Liverpool, Amsterdam, 
and Brest provide readings of tidal high and/or low 
water levels back into the seventeenth century. Addi 
tionally, Talke and Jay (2013) recently pointed to the 
availability of records in the Pacific and western Atlantic 
region going back to the mid-nineteenth century with 
more than 50 records available from 1900 onward. The 
analysis of these valuable and more or less robust ocean 
ographic measurements could be of high importance for 
the analysis of storms going into times for which only 
a few conventional proxies for storminess exist. 
Despite the fact that surges measure changes in wind 
speed and direction, the analysis of high annual per 
centiles of surges at Cuxhaven confirms earlier observa 
tional studies on storminess over the European-Atlantic 
region with conventional proxies (Schmidt and von 
Storch 1993; Alexandersson et al. 1998, 2000; Barring 
and von Storch 2004; Matulla et al. 2008; Hanna et al. 
2008; Wang et al. 2009) in terms of both variability and 
trends. Consistent with the different pressure-based 
storm indices of the last up to 150 yr, periods of in 
creased storminess with higher occurrence of extreme 
storm surges prevailed at the end of the nineteenth 
and twentieth century, with very low levels in the 1970s. 
While we could identify a considerable interannual-to- 
multidecadal variability, which is significantly correlated 
to large-scale atmospheric variability over the North 
Atlantic and European region, no robust long-term 
trend could be detected in surges since 1843 at the tide 
gauge of Cuxhaven. The absence of any robust long 
term trends in annual storminess in observations of the 
last up to 170 yr over the Euro-Atlantic region seems to 
support global modeling results of externally forced 
coupled atmosphere-ocean general circulation models 
(AOGCM). They indicate no long-term changes in 
storminess (Fischer-Bruns et al. 2005) or cyclone char 
acteristics (Xia et al. 2012) for the Northern Hemisphere 
through the last millennium, although most AOGCM's 
point to an increase in storminess under enhanced green 
house gas emission in a future climate (e.g., Gastineau and 
Soden 2009; Pinto et al. 2007; Donat et al. 2011a). 
By applying a simple statistical model to reanalysis 
(20CRv2) winds and SLP over the North Sea, we have 
further reconstructed storm surges in the German Bight 
over the entire reanalysis period since 1871. Based on 
the ensemble mean as well as the ensemble spread, we 
demonstrated that the re analysis data have a high pre 
dictive skill back to the 1910s, while previously the 
model skill decreases considerably leading to lower oc 
currence of extreme storm surges in the first four to five 
decades of the reanalysis. This decrease in storminess is 
visible in neither surge observations at Cuxhaven nor 
different pressure-based storm indices (Krueger et al. 
2013a,b) over the European-Atlantic region. Hence, the 
significant positive trends detected in 20CRv2 stormi 
ness by Donat et al. (2011b) appears to be less a result of 
the large decadal trends in storminess in the last decades 
but rather reflects the lower occurrences of extreme 
winds in the early decades of the reanalysis. In contrast 
to the results from Krueger et al. (2013b), which are 
partly from a different region, our study points to in 
creasing inconsistencies between reanalysis and obser 
vation data before the 1910s. The inconsistencies and 
their dating are supported by each ensemble member as 
well as the ensemble mean. As the link of surge levels at 
Cuxhaven with the fully independent NSCI remains 
stationary back to 1850, the discrepancies with 20CRv2 
are unlikely to be explained with inconsistencies in the 
surge record. Thus, we conclude that the 20CRv2 rep 
resents a useful database for the North Sea region from 
the beginning of the twentieth century, but one has to be 
careful by computing linear trends, particularly when 
periods before 1910 are included in the analysis. 
We further recommend the presented methods as an 
independent quality check of reanalysis and tide gauge 
data in other regions of the world. Especially in regions 
where meteorological observations are sparse, the cross 
validation with homogeneous tide gauge data might 
provide information on the consistency of reanalysis 
data on longer time scales. In turn, in regions where the 
tide gauge network is sparse, homogenous reanalysis 
data may provide information on the homogeneity of 
sea level measurements. In case of inconsistencies in the 
long-term variations between reanalysis and sea level 
observations, an independent pressure index like the 
NSCI for the German Bight can be established from 
observations to study the robustness of the local obser 
vations or reanalysis data relative to this index. Whether 
a similar link between large-scale forcing (pressure and 
wind) and local surges can be also established (e.g., in 
tropical regions) needs to be evaluated. The homoge 
neity of observations and reanalysis data are indispens 
able for oceanographers and meteorologists to study 
multidecadal variations or trends in storminess or ex 
change processes between the atmosphere and the ocean, 
which is in turn an important step in understanding the 
predictability of the system. 
Acknowledgments. We highly acknowledge four anon 
ymous reviewers for their valuable comments. We further 
thank the Twentieth Century Reanalysis team for pro 
viding the dataset without any charge. Support for the 
Twentieth Century Reanalysis Project dataset is pro 
vided by the U.S. Department of Energy, Office of 
Science Innovative and Novel Computational Impact