Climate in Nordic historical research – a research review and future perspectives

This article assesses the development and current state of climate history research conducted in the five Nordic countries and Estonia. The possible societal impacts of past climatic changes already interested a handful of Nordic historians in the early twentieth century, but the lack of data on past climate fluctuations constrained scholarship in this field until recently. The data availability has increased fundamentally over the past decades due to the advances of palaeoclimatology. However, these advances have created new challenges, related to the ability to utilize data from the natural sciences in historical research as well as acquiring a basic knowledge on climatology. In many European countries, climate history has established itself as a strong academic subfield and consequently has created approaches as to how to overcome some main pitfalls, like climate determinism, related to the early works in the field. These epistemological advances are just beginning to gain a foothold in Nordic historical research. Thus, the article concludes with ten recommendations to improve future research in Nordic climate history

Bannlyst kung av Guds nåde

This article investigates how Sverrir Sigurðarson, ruler of Norway between 1177 and 1202, is ideologically legitimised as king in the biography Sverris saga. In previous research, the perception that Sverrir is portrayed as a Christian rex iustus has competed with the perception that Sverrir is depicted as a traditional Old Norse warrior king, who gains his legitimacy through his military successes. This article demonstrates that the rex iustus idea is central in the saga when it comes to legitimising Sverrir, and that his seizure of power is also placed in the salvation-historical worldview of the time. Fully in accordance with the way contemporary continental European kings legitimised their claims to power, Sverrirââ¬â¢s royal power is justified in the saga through a combination of the notion that God has chosen Sverrir as king and the notion of a line of succession to the throne through paternal blood ties. The article also demonstrates that the saga, like the polemic pamphlet A Speech against the Bishops (Ett tal mot biskoparna), propagates against the perception that the Church is above the royal power and dismisses the Churchââ¬â¢s excommunication of Sverrir as unjust and invalid

Climate and society in European history

This article evaluates 165 studies from various disciplines, published between 2000 and 2019, which in different ways link past climate variability and change to human history in medieval and early modern Europe (here, c. 700–1815 CE). Within this review, we focus on the identification and interpretation of causal links between changes in climate and in human societies. A revised climate–society impact order model of historical climate–society interactions is presented and applied to structure the findings of the past 20 years' scholarship. Despite considerable progress in research about past climate–society relations, partly expedited by new palaeoclimate data, we identify limitations to knowledge, including geographical biases, a disproportional attention to extremely cold periods, and a focus on crises. Furthermore, recent scholarship shows that the limitations with particular disciplinary approaches can be successfully overcome through interdisciplinary collaborations. We conclude the article by proposing recommendations for future directions of research in the climatic change–human history nexus

A millennium-long reconstruction of damaging hydrological events across Italy.

Damaging hydrological events are extreme phenomena with potentially severe impacts on human societies. Here, we present the hitherto longest reconstruction of damaging hydrological events for Italy, and for the whole Mediterranean region, revealing 674 such events over the period 800-2017. For any given year, we established a severity index based on information in historical documentary records, facilitating the transformation of the data into a continuous time-series. Episodes of hydrological extremes disrupted ecosystems during the more severe events by changing landforms. The frequency and severity of damaging hydrological events across Italy were likely influenced by the mode of the Atlantic Multidecadal Variability (AMV), with relatively few events during the warm Medieval Climate Anomaly dominated by a positive phase of the AMV. More frequent and heavier storms prevailed during the cold Little Ice Age, dominated by a more negative phase of the AMV. Since the mid-19th century, a decreasing occurrence of exceptional hydrological events is evident, especially during the most recent decades, but this decrease is not yet unprecedented in the context of the past twelve centuries

Author Correction: A millennium-long reconstruction of damaging hydrological events across Italy

An amendment to this paper has been published and can be accessed via a link at the top of the paper

Causes of East Asian temperature multidecadal variability since 850 CE

The drivers of multidecadal to centennial‐scale variability in East Asian temperature, apparent in temperature reconstructions, are poorly understood. Here, we apply a multivariate regression analysis to distinguish the influences of large‐scale modes of internal variability (Atlantic Multidecadal Oscillation, AMO; and Pacific Multidecadal Oscillation, PMO), and external natural (orbital, solar and volcanic) and anthropogenic (greenhouse gas concentrations, aerosols, and land use changes) forcings on East Asian warm‐season temperature over the period 850–1999 AD. We find that ~80% of the temperature change on timescales longer than 30 years can be explained including all drivers over the full‐length period. The PMO was the most important driver of multidecadal temperature variability during the Medieval Climate Anomaly (here, 950–1250), while solar contribution was important during the Little Ice Age (here, 1350–1850). Since 1850, two‐thirds of temperature change can be explained with anthropogenic forcing, whereas one‐third was related mainly to the AMO and volcanic forcing

Initiation of a Stable Convective Hydroclimatic Regime in Central America Circa 9000 Years BP

Many Holocene hydroclimate records show rainfall changes that vary with local orbital insolation. However, some tropical regions display rainfall evolution that differs from gradual precessional pacing, suggesting that direct rainfall forcing effects were predominantly driven by sea-surface temperature thresholds or inter-ocean temperature gradients. Here we present a 12,000 yr continuous U/Th-dated precipitation record from a Guatemalan speleothem showing that Central American rainfall increased within a 2000 yr period from a persistently dry state to an active convective regime at 9000 yr BP and has remained strong thereafter. Our data suggest that the Holocene evolution of Central American rainfall was driven by exceeding a temperature threshold in the nearby tropical oceans. The sensitivity of this region to slow changes in radiative forcing is thus strongly mediated by internal dynamics acting on much faster time scales

Regional Patterns of Late Medieval and Early Modern European Building Activity Revealed by Felling Dates

Fredrik Charpentier Ljungqvist, Andrea Seim, Willy Tegel, Paul J. Krusic, Claudia Baittinger, Christelle Belingard, Mauro Bernabei, Niels Bonde, Paul Borghaerts, Yann Couturier, Anne Crone, Sjoerd van Daalen, Aoife Daly, Petra Doeve, Marta Domínguez-Delmás, Jean-Louis Edouard, Thomas Frank, Christian Ginzler, Michael Grabner, Friederike M. Gschwind, Kristof Haneca, Anton Hansson, Franz Herzig, Karl-Uwe Heussner, Jutta Hofmann, David Houbrechts, Ryszard Jerzy Kaczka, Tomáš Kolář, Raymond Kontic, Tomáš Kyncl, Vincent Labbas, Per Lagerås, Yannick Le Digol, Melaine Le Roy, Hanns Hubert Leuschner, Hans Linderson, Francis Ludlow, Axel Marais, Coralie M. Mills, Mechthild Neyses-Eiden, Kurt Nicolussi, Christophe Perrault, Klaus Pfeifer, Michal Rybníček, Andreas Rzepecki, Martin Schmidhalter, Mathias Seifert, Lisa Shindo, Barbara Spyt, Josué Susperregi, Helene Løvstrand Svarva, Terje Thun, Felix Walder, Tomasz Ważny, Elise Werthe, Thorsten Westphal, Rob Wilson, Ulf BüntgenAlthough 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

New perspective on spring vegetation phenology and global climate change based on Tibetan Plateau tree-ring data

Phenological responses of vegetation to climate, in particular to the ongoing warming trend, have received much attention. However, divergent results from the analyses of remote sensing data have been obtained for the Tibetan Plateau (TP), the world's largest high-elevation region. This study provides a perspective on vegetation phenology shifts during 1960-2014, gained using an innovative approach based on a well-validated, process-based, tree-ring growth model that is independent of temporal changes in technical properties and image quality of remote sensing products. Twenty composite site chronologies were analyzed, comprising about 3,000 trees from forested areas across the TP. We found that the start of the growing season (SOS) has advanced, on average, by 0.28 d/y over the period 1960-2014. The end of the growing season (EOS) has been delayed, by an estimated 0.33 d/y during 1982-2014. No significant changes in SOS or EOS were observed during 1960-1981. April-June and August-September minimum temperatures are the main climatic drivers for SOS and EOS, respectively. An increase of 1 °C in April-June minimum temperature shifted the dates of xylem phenology by 6 to 7 d, lengthening the period of tree-ring formation. This study extends the chronology of TP phenology farther back in time and reconciles the disparate views on SOS derived from remote sensing data. Scaling up this analysis may improve understanding of climate change effects and related phenological and plant productivity on a global scale

Higher groundwater levels in western Europe characterize warm periods in the Common Era.

Funder: Projekt DEALHydroclimate, the interplay of moisture supply and evaporative demand, is essential for ecological and agricultural systems. The understanding of long-term hydroclimate changes is, however, limited because instrumental measurements are inadequate in length to capture the full range of precipitation and temperature variability and by the uneven distribution of high-resolution proxy records in space and time. Here, we present a tree-ring-based reconstruction of interannual to centennial-scale groundwater level (GWL) fluctuations for south-western Germany and north-eastern France. Continuously covering the period of 265-2017 CE, our new record from the Upper Rhine Valley shows that the warm periods during late Roman, medieval and recent times were characterized by higher GWLs. Lower GWLs were found during the cold periods of the Late Antique Little Ice Age (LALIA; 536 to ~ 660 CE) and the Little Ice Age (LIA; between medieval and recent warming). The reconstructed GWL fluctuations are in agreement with multidecadal North Atlantic climate variability derived from independent proxies. Warm and wet hydroclimate conditions are found during warm states of the Atlantic Ocean and positive phases of the North Atlantic Oscillation on decadal scales