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Europe’s recent summer droughts have had devastating ecological and economic consequences, but the severity and cause of these extremes remain unclear. Here we present 27,080 annually resolved and absolutely dated measurements of tree-ring stable carbon and oxygen (δ13C and δ18O) isotopes from 21 living and 126 relict oaks (Quercusspp.) used to reconstruct central European summer hydroclimate from 75 bceto 2018 ce. We find that the combined inverse δ13C and δ18O values correlate with the June–August Palmer Drought Severity Index from 1901–2018 at 0.73 (P< 0.001). Pluvials around 200, 720 and 1100 ce, and droughts around 40, 590, 950 and 1510 ceand in the twenty-first century, are superimposed on a multi-millennial drying trend. Our reconstruction demonstrates that the sequence of recent European summer droughts since 2015 ceis unprecedented in the past 2,110 years. This hydroclimatic anomaly is probably caused by anthropogenic warming and associated changes in the position of the summer jet stream.

ABSTRACTAs the worldwide standard for radiocarbon (14C) dating over the past ca. 50,000 years, the International Calibration Curve (IntCal) is continuously improving towards higher resolution and replication. Tree-ring-based 14C measurements provide absolute dating throughout most of the Holocene, although high-precision data are limited for the Younger Dryas interval and farther back in time. Here, we describe the dendrochronological characteristics of 1448 new 14C dates, between ~11,950 and 13,160 cal BP, from 13 pines that were growing in Switzerland. Significantly enhancing the ongoing IntCal update (IntCal20), this Late Glacial (LG) compilation contains more annually precise 14C dates than any other contribution during any other period of time. Thus, our results now provide unique geochronological dating into the Younger Dryas, a pivotal period of climate and environmental change at the transition from LG into Early Holocene conditions.

A recent archaeological discovery of a Late Bronze Age cartwheel in north eastern France (Erstein, Alsace) has shed important new light on the technical development of wheels in Europe. The well-preserved wooden fragments were discovered at the base of a water well and were in secondary use as wedges to adjust a well lined with a hollowed tree trunk. Dendrochronological and radiocarbon results gave a chronological classification to the Late Bronze Age in 13th century BCE. Although the discovered wheel was not complete, these fragments provide a clear picture of the overall wheel design and allow a detailed reconstruction. The wheel disc comprises three parts that are held together by stump tenon joints and two mutually curved insertion strips with dovetail profiles that are located on opposite sides. The two outer boards have crescent-shaped cut-outs. The planks for the disc wheel were crafted from sycamore maple (Acer pseudoplatanus), and the strips and tenons were crafted from hazel (Corylus avellana) and ash (Fraxinus excelsior), respectively. The results of wood identification indicate that the selection and processing of wood were predominantly based on specific knowledge and supra-regional traditions. The recent find from Erstein is also compared with what is currently known from other Bronze Age sources from Europe. Together, these results clearly demonstrate that there were almost no regional variations in construction techniques from south of the Alps to northern Europe.

Climatic changes during the first half of the Common Era have been suggested to play a role in societal reorganizations in Europe and Asia. In particular, the sixth century coincides with rising and falling civilizations, pandemics, human migration and political turmoil. Our understanding of the magnitude and spatial extent as well as the possible causes and concurrences of climate change during this period is, however, still limited. Here we use tree-ring chronologies from the Russian Altai and European Alps to reconstruct summer temperatures over the past two millennia. We find an unprecedented, long-lasting and spatially synchronized cooling following a cluster of large volcanic eruptions in 536, 540 and 547 AD (ref. ), which was probably sustained by ocean and sea-ice feedbacks, as well as a solar minimum. We thus identify the interval from 536 to about 660 AD as the Late Antique Little Ice Age. Spanning most of the Northern Hemisphere, we suggest that this cold phase be considered as an additional environmental factor contributing to the establishment of the Justinian plague, transformation of the eastern Roman Empire and collapse of the Sasanian Empire, movements out of the Asian steppe and Arabian Peninsula, spread of Slavic-speaking peoples and political upheavals in China.

AbstractRecent findings indicated spruce from North America and larch from eastern Siberia to be the dominating tree species of Arctic driftwood throughout the Holocene. However, changes in source region forest and river characteristics, as well as ocean current dynamics and sea ice extent likely influence its spatiotemporal composition. Here, we present 2556 driftwood samples from Greenland, Iceland, Svalbard, and the Faroe Islands. A total of 498 out of 969 Pinussylvestrisring width series were cross-dated at the catchment level against a network of Eurasian boreal reference chronologies. The central Siberian Yenisei and Angara Rivers account for 91% of all dated pines, with their outermost rings dating between 1804 and 1999. Intensified logging and timber rafting along the Yenisei and Angara in the mid-20th century, together with high discharge rates, explain the vast quantity of material from this region and its temporal peak ca. 1960. Based on the combined application of wood-anatomical and dendrochronological techniques on a well-replicated data set, our results question the assumption that Arctic driftwood mainly consists of millennial-old larch and spruce. Nevertheless, data from other species and regions, together with longer boreal reference chronologies, are needed for generating reliable proxy archives at the interface of marine and terrestrial environments.