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FCL and AS were supported by the Swedish Research Council (Vetenskapsrådet, grant no. 2018-01272). FCL conducted the work with this article as a Pro Futura Scientia XIII Fellow funded by the Swedish Collegium for Advanced Study through Riksbankens Jubileumsfond. WT was supported by the German Research Foundation (DFG, TE 613/3-1). AD received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement no. 677152). AH was supported by Riksbankens Jubileumsfond (grant no. IN20-0026). MD-D was funded by the Dutch Research Council (Nederlandse organisatie voor Wetenschappelijk Onderzoek, grant no. 016.Veni.195.502). TK, MR, and UB were supported the SustES project – “Adaptation strategies for sustainable ecosystem services and food security under adverse environmental conditions” (CZ.02.1.01/0.0/0.0/16_019/0000797). LS was supported by Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Germany’s Excellence Strategy – EXC 2150 ROOTS – 390870439. FL was supported by a European Research Council (ERC) Synergy Grant (4-OCEANS; grant agreement no. 951649) under the European Union’s Horizon 2020 research and innovation programme. Although variations in building activity are a useful indicator of societal well-being and demographic development, historical datasets for larger regions and longer periods are still rare. Here, we present 54,045 annually precise dendrochronological felling dates from historical construction timber from across most of Europe between 1250 and 1699 CE to infer variations in building activity. We use geostatistical techniques to compare spatiotemporal dynamics in past European building activity against independent demographic, economic, social and climatic data. We show that the felling dates capture major geographical patterns of demographic trends, especially in regions with dense data coverage. A particularly strong negative association is found between grain prices and the number of felling dates. In addition, a significant positive association is found between the number of felling dates and mining activity. These strong associations, with well-known macro-economic indicators from pre-industrial Europe, corroborate the use of felling dates as an independent source for exploring large-scale fluctuations of societal well-being and demographic development. Three prominent examples are the building boom in the Hanseatic League region of northeastern Germany during the 13th century, the onset of the Late Medieval Crisis in much of Europe c. 1300, and the cessation of building activity in large parts of central Europe during armed conflicts such as the Thirty Years’ War (1618–1648 CE). Despite new insights gained from our European-wide felling date inventory, further studies are needed to investigate changes in construction activity of high versus low status buildings, and of urban versus rural buildings, and to compare those results with a variety of historical documentary sources and natural proxy archives. Publisher PDF

Though tree-ring chronologies are annually resolved, their dating has never been independently validated at the global scale. Moreover, it is unknown if atmospheric radiocarbon enrichment events of cosmogenic origin leave spatiotemporally consistent fingerprints. Here we measure the 14C content in 484 individual tree rings formed in the periods 770–780 and 990–1000 CE. Distinct 14C excursions starting in the boreal summer of 774 and the boreal spring of 993 ensure the precise dating of 44 tree-ring records from five continents. We also identify a meridional decline of 11-year mean atmospheric radiocarbon concentrations across both hemispheres. Corroborated by historical eye-witness accounts of red auroras, our results suggest a global exposure to strong solar proton radiation. To improve understanding of the return frequency and intensity of past cosmic events, which is particularly important for assessing the potential threat of space weather on our society, further annually resolved 14C measurements are needed., Nature Communications, 9, ISSN:2041-1723

Sediment budgeting concepts serve as quantification tools to decipher the erosion and accumulation processes within a catchment and help to understand these relocation processes through time. While sediment budgets are widely used in geomorphological catchment‐based studies, such quantification approaches are rarely applied in geoarchaeological studies. The case of Charlemagne's summit canal (also known as Fossa Carolina) and its erosional collapse provides an example for which we can use this geomorphological concept and understand the abandonment of the Carolingian construction site. The Fossa Carolina is one of the largest hydro‐engineering projects in Medieval Europe. It is situated in Southern Franconia (48.9876°N, 10.9267°E; Bavaria, southern Germany) between the Altmühl and Swabian Rezat rivers. It should have bridged the Central European watershed and connected the Rhine–Main and Danube river systems. According to our dendrochronological analyses and historical sources, the excavation and construction of the Carolingian canal took place in AD 792 and 793. Contemporary written sources describe an intense backfill of excavated sediment in autumn AD 793. This short‐term erosion event has been proposed as the principal reason for the collapse and abandonment of the hydro‐engineering project. We use subsurface data (drillings, archaeological excavations, and direct‐push sensing) and geospatial data (a LiDAR digital terrain model (DTM), a pre‐modern DTM, and a 3D model of the Fossa Carolina] for the identification and sediment budgeting of the backfills. Dendrochronological findings and radiocarbon ages of macro remains within the backfills give clear evidence for the erosional collapse of the canal project during or directly after the construction period. Moreover, our quantification approach allows the detection of the major sedimentary collapse zone. The exceedance of the manpower tipping point may have caused the abandonment of the entire construction site. The spatial distribution of the dendrochronological results indicates a north–south direction of the early medieval construction progress. © 2020 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd, The sediment budgeting concept as erosion and accumulation quantification tool helps in understanding the abrupt backfilling of excavated material in the construction pit, which may have forced the abandonment of the Carolingian canal in southern Germany at the end of the year AD 793. The backfill sediments could be dated precisely through radiocarbon dating of macro remains and dendrochronology of excavated timbers. These timbers recovered in three different archaeological excavation trenches reveal a Carolingian construction progress from North to South., Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659