Multi-proxy dating of Iceland's major pre-settlement Katla eruption to 822-823 CE

Investigations of the impacts of past volcanic eruptions on climate, environment, and society require accurate chronologies. However, eruptions that are not recorded in historical documents can seldom be dated exactly. Here we use annually resolved radiocarbon ($^{14}$C) measurements to isolate the 775 CE cosmogenic $^{14}$C peak in a subfossil birch tree that was buried by a glacial outburst flood in southern Iceland. We employ this absolute time marker to date a subglacial eruption of Katla volcano at late 822 CE to early 823 CE. We argue for correlation between the 822–823 CE eruption and a conspicuous sulfur anomaly evident in Greenland ice cores, which follows in the wake of an even larger volcanic signal (ca. 818–820 CE) as yet not attributed to a known eruption. An abrupt summer cooling in 824 CE, evident in tree-ring reconstructions for Fennoscandia and the Northern Hemisphere, suggests a climatic response to the Katla eruption. Written historical sources from Europe and China corroborate our proposed tree ring–radiocarbon–ice core linkage but also point to combined effects of eruptions occurring during this period. Our study describes the oldest precisely dated, high-latitude eruption and reveals the impact of an extended phase of volcanic forcing in the early 9$^{th}$ century. It also provides insight into the existence of prehistoric woodland cover and the nature of volcanism several decades before Iceland's permanent settlement began.U. Büntgen received funding from the Ministry of Education, Youth and Sports of CR within the National Sustainability Program I (NPU I; GN LO1415), and additional support was provided by NSF grant 0909541. We are particularly thankful to the NEEM project and its participants

A risk society? Environmental hazards, risk and resilience in the later Middle Ages in Europe

Modern society is said to have restructured in reaction to contemporary hazards with the aim of improving its management of risk. This implies that pre-industrial societies were somehow fundamentally different. In this paper, we challenge that hypothesis by examining the ways in which risks associated with environmental hazards were managed and mitigated during the Middle Ages (defined here as the period from 1000 to 1550 AD). Beginning with a review of the many case studies of rapid onset disasters across Europe, we draw upon both historical and archaeological evidence and architectural assessments of structural damage for what is a pre-instrumental period. Building upon this, the second part of the paper explores individual outlooks on risk, emphasising the diversity of popular belief and the central importance of Christianity in framing attitudes. Despite their religious perspectives, we find that medieval communities were not helpless in the face of serious environmental hazards. We argue instead that the response of society to these threats was frequently complex, considered and, at times, surprisingly modern