There are concerns that recent climate change is altering the frequency and magnitudes of river floods in an unprecedented way 1 . Historical studies have identified flood-rich periods in the past half millennium in various regions of Europe 2 . However, because of the low temporal resolution of existing data sets and the relatively low number of series across Europe, it has remained unclear whether Europe is currently in a flood-rich period from a long term perspective. We analyze how recent decades compare with the flood history of Europe, using a new database composed of more than 100 high-resolution (sub-annual) historical flood series based on documentary evidence covering all major regions of Europe. Here we show that the past three decades were among the most flood-rich periods in Europe in the last 500 years, and that this period differs from other floodrich periods in terms of its extent, air temperatures and flood seasonality. We identified nine floodrich periods and associated regions. Among the periods richest in floods are 1560-1580 (Western and Central Europe), 1760-1800 (most of Europe), 1840-1870 (Western and Southern Europe), and 1990. In most parts of Europe previous flood-rich periods occurred during cooler than usual phases, however the current flood-rich period has been much warmer. In the past, the dominant flood seasons in flood-rich periods were similar to those during the intervening (interflood) periods, but flood seasonality is more pronounced in the recent period. For example, during previous flood and interflood periods, 41% and 42% of Central European floods occurred in summer respectively, compared to 55% of floods in the recent period. The uniqueness of the present-day flood-rich period calls for process-based flood risk assessment tools and flood risk management strategies that can incorporate these changes.
Abstract. Weather diaries constitute an important source of data
for historical climatology, employed in the analysis of weather patterns for
both the pre-instrumental and the early instrumental periods. Among the many
weather diaries that exist in Europe, the daily records kept by the Reverend
Šimon Hausner from Buchlovice in south-east Moravia (Czech Republic),
covering the 1803–1831 period, are particularly useful. His qualitative
daily weather descriptions enable the construction of series for
temperature, precipitation, cloudiness, wind, and other weather phenomena
(particularly thunderstorms and fogs), supplemented by a number of
phenological and agricultural work records. His data related to temperature
and precipitation patterns were quantified into a series of weighted
temperature and precipitation indices on 7-degree scales, which were
subsequently compared with standard meteorological observations from the
secular meteorological station in Brno. This comparison indicates that
Hausner's observations are highly reliable and confirms the importance of
his data for a better understanding of the variability in the regional
climate in the period of early instrumental measurements in Moravia. At the
same time, it reveals the importance of weather-related documentary data in
the overlap period with instrumental meteorological observations.
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