Changes in climate affected human societies throughout the last millennium. While European cold periods in the 17th and 18th century have been assessed in detail, earlier cold periods received much less attention due to sparse information available. New evidence from proxy archives, historical documentary sources and climate model simulations permit us to provide an interdisciplinary, systematic assessment of an exceptionally cold period in the 15th century. Our assessment includes the role of internal, unforced climate variability and external forcing in shaping extreme climatic conditions and the impacts on and responses of the medieval society in north-western and central Europe. Climate reconstructions from a multitude of natural and anthropogenic archives indicate that the 1430s were the coldest decade in north-western and central Europe in the 15th century. This decade is characterised by cold winters and average to warm summers resulting in a strong seasonal cycle in temperature. Results from comprehensive climate models indicate consistently that these conditions occurred by chance due to the partly chaotic internal variability within the climate system. External forcing like volcanic eruptions tends to reduce simulated temperature seasonality and cannot explain the reconstructions. The strong seasonal cycle in temperature reduced food production and led to increasing food prices, a subsistence crisis and a famine in parts of Europe. Societies were not prepared to cope with failing markets and interrupted trade routes. In response to the crisis, authorities implemented numerous measures of supply policy and adaptation such as the installation of grain storage capacities to be prepared for future food production shortfalls
Abstract. Heavy precipitation on the south side of the central Alps produced a catastrophic flood in October 1868. We assess the damage and societal impacts, as well as the atmospheric and hydrological drivers using documentary evidence, observations and novel numerical weather and runoff simulations. The greatest damage was concentrated close to the Alpine divide and Lago Maggiore. An atmospheric reanalysis emphasizes the repeated occurrence of streamers of high potential vorticity as precursors of heavy precipitation. Dynamical downscaling indicates high freezing levels (4000 m a.s.l.), extreme precipitation rates (max. 270 mm 24 h−1) and weather dynamics that agree well with observed precipitation and damage, and with existing concepts of forced low-level convergence, mid-level uplift and iterative northeastward propagation of convective cells. Simulated and observed peak levels of Lago Maggiore differ by 2 m, possibly because the exact cross section of the lake outflow is unknown. The extreme response of Lago Maggiore cannot be attributed to low forest cover. Nevertheless, such a paradigm was adopted by policy makers following the 1868 flood, and used to implement nationwide afforestation policies and hydraulic structures. These findings illustrate the potential of high-resolution, hydrometeorological models – strongly supported by historical methods – to shed new light on weather events and their socio-economic implications in the 19th century.
Abstract. Droughts derive from a precipitation deficit and can also be temperature driven. They are dangerous natural hazards for human societies. Documentary data from the pre-modern and early modern times contain direct and indirect information on precipitation that allow for the production of reconstructions using historical climatology methods. For this study, two drought indices – the drought index of Bern (DIB) and the drought index of Rouen (DIR) – have been created on the basis of documentary data produced in Bern, Switzerland, and Rouen, France, respectively for the period from 1315 to 1715. These two indices have been compared to a third supra-regional drought index (SDI) for Switzerland, Germany, France, the Netherlands, and Belgium that was synthesised from precipitation reconstruction based on historical climatology. The results of this study show that the documentary data from Bern mainly contain summer droughts, whereas the data from Rouen rather allow for the reconstruction of spring droughts. The comparison of the three above-mentioned indices shows that the DIB and the DIR most probably do not contain all of the actual drought events; however, they detect droughts that do not appear in the SDI. This fact suggests that more documentary data from single locations, such as historical city archives, should be examined in the future and should be added to larger reconstructions in order to obtain more complete drought reconstructions.
Abstract. Heavy precipitation on the south side of the central Alps produced a catastrophic flood in October 1868. We assess the damage and societal impacts, as well as the atmospheric and hydrological drivers using documentary evidence, observations, and novel numerical weather and runoff simulations. The greatest damage was concentrated close to the Alpine divide and Lago Maggiore. An atmospheric reanalysis emphasizes the repeated occurrence of streamers of high potential vorticity as precursors of heavy precipitation. Dynamical downscaling indicates high freezing levels (4000 m a.s.l.), extreme precipitation rates (max. 270 mm/24 h), and weather dynamics that agree well with observed precipitation and damage, and with existing concepts of forced low-level convergence, mid-level uplift and iterative northeastward propagation of convective cells. Simulated and observed peak levels of Lago Maggiore differ by 2 m, possibly because the exact cross-section of the lake outflow is unknown. The extreme response of Lago Maggiore cannot be attributed to low forest cover. Nevertheless, such a paradigm was adopted by policy makers following the 1868 flood, and used to implement nationwide afforestation policies and hydraulic structures. These findings illustrate the potential of high-resolution, hydro-meteorological models – strongly supported by historical methods – to shed new light on weather events and their socio-economic implications in the 19th century.
Abstract. Throughout the last millennium, mankind was affected by prolonged deviations from the climate mean state. While periods like the Maunder Minimum in the 17th century have been assessed in greater detail, earlier cold periods such as the 15th century received much less attention due to the sparse information available. Based on new evidence from different sources ranging from proxy archives to model simulations, it is now possible to provide an end-to-end assessment about the climate state during an exceptionally cold period in the 15th century, the role of internal, unforced climate variability and external forcing in shaping these extreme climatic conditions, and the impacts on and responses of the medieval society in Central Europe. Climate reconstructions from a multitude of natural and human archives indicate that, during winter, the period of the early Spörer Minimum (1431–1440 CE) was the coldest decade in Central Europe in the 15th century. The particularly cold winters and normal but wet summers resulted in a strong seasonal cycle that challenged food production and led to increasing food prices, a subsistence crisis, and a famine in parts of Europe. As a consequence, authorities implemented adaptation measures, such as the installation of grain storage capacities, in order to be prepared for future events. The 15th century is characterised by a grand solar minimum and enhanced volcanic activity, which both imply a reduction of seasonality. Climate model simulations show that periods with cold winters and strong seasonality are associated with internal climate variability rather than external forcing. Accordingly, it is hypothesised that the reconstructed extreme climatic conditions during this decade occurred by chance and in relation to the partly chaotic, internal variability within the climate system.
Abstract. Droughts derive from a deficit of precipitation and belong to the most dangerous natural hazards for human societies. Documentary data of the pre-modern and early modern times contain direct and indirect information on precipitation that allow the production of reconstructions with the methods of historical climatology. For this study, two drought indices have been created on the basis of documentary data produced in Bern, Switzerland (DIB) and in Rouen, France (DIR) for the period from 1315 to 1715. These two indices have been compared to a third supra-regional drought index for Switzerland (SDI), Germany, France, the Netherlands, and Belgium synthesised from precipitation reconstruction based on historical climatology. The results of the study show that the documentary data from Bern mainly contain summer droughts, whereas the data from Rouen rather allow the reconstruction of spring droughts. The comparison of the three indices shows that the DIB and the DIR most probably do not contain all actual drought events, but they also detect droughts that do not appear in the SDI. This fact suggests that more documentary data from single places, such as historical city archives, should be examined in the future and added to larger reconstructions in order to obtain more complete drought reconstructions.
Das im Süden der Stadt Bern liegende Gürbetal ist aufgrund der naturräumlichen Gegebenheiten eine stark hochwassergefährdete Gegend. Immer wieder trägt die Gürbe viel Wasser und Geschiebe ins Tal und verursacht Überschwemmungen. Über viele Jahrhunderte konnten die Anwohner nur punktuelle Schutzmassnahmen vornehmen. Der Talboden versumpfte und war kaum nutzbar. Dies änderte sich um die Mitte des 19. Jahrhunderts, als sich ein tiefgreifender Wandel im Umgang mit der Hochwassergefahr vollzog. Durch Fortschritte in Wissenschaft und Technik, Veränderungen der politischen Gegebenheiteun und des Naturverständnisses rückten nun umfassende Flusskorrektionen in den Bereich des Möglichen. Eine Häufung von schweren Überschwemmungen und der Landhunger der wachsenden Bevölkerung verstärkten das Bedürfnis nach einer Bändigung des Flusses. Im Zuge der Grossen Gürbekorrektion (1855–1881) wurde das Gewässer im Unterlauf kanalisiert und im Oberlauf durch Wildbachverbauungen gesichert. Obwohl sich die Lage dadurch verbesserte, konnten die häufigen Überschwemmungen nicht wie gewünscht verhindert werden. In zahlreichen Projekten wurde das Verbauungswerk nach und nach erweitert. Bis heute werden an der Gürbe umfangreiche Hochwasserschutzprojekte umgesetzt.
Die Studie untersucht die Entwicklung des Hochwasserschutzes an der Gürbe im Zeitraum von 1855 bis 2010 aus breiter Perspektive. Da aufgrund der stets wiederkehrenden schadenbringenden Überschwemmungen seit 1855 ununterbrochen grosse Präventionsprojekte umgesetzt wurden, kann beispielhaft aufgezeigt werden, wie sich der Hochwasserschutz veränderte. Hierbei sind nicht nur die technischen Entwicklungen, sondern vor allem auch der Philosophiewandel interessant. Die Autorin zeigt auf, wie die vorherrschenden Schutzkonzepte auf der lokalen Ebene umgesetzt wurden, welche Erwartungen und Hoffnungen mit den Massnahmen verbunden waren, welche Konflikte sich ergaben und welche Auswirkungen die Hochwasservorkehrungen hatten.
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