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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 (δ 13 C and δ 18 O) isotopes from 21 living and 126 relict oaks ( Quercus spp.) used to reconstruct central European summer hydroclimate from 75  bce to 2018  ce . We find that the combined inverse δ 13 C and δ 18 O 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  ce and 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  ce is 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. European summer droughts in recent years are anomalously severe compared with those of the previous 2,000 years, according to a synthesis of annually resolved tree-ring carbon and oxygen isotope records.

Les sites gallo-romains du nord des Alpes sont peu nombreux à avoir livré autant de bois de construction que celui du boulevard Dr Henri-Henrot à Reims, surtout dans un tel état de conservation. Pour obtenir une datation précise des pièces de bois employées, la méthode utilisée ici, connue sous le nom de dendrochronologie, se fonde sur l’examen des cernes. La réponse aux questions d’ordre chronologique forme la base de cette analyse, qui se prolonge avec la mise en relation des informations recueillies et des questionnements archéologiques. Les datations ainsi obtenues fournissent des points d’ancrage pour l’histoire de l’occupation de la périphérie méridionale de la ville antique de Reims. Le nombre exceptionnel de bois sur le site permet également d’informer non seulement sur l’état de la forêt à cette époque, mais aussi sur sa gestion, qui peuvent être tous deux liés à l’évolution des conditions environnementales et aux processus socio-économiques. By virtue of being located partially within the former river bed of the Vesle’s right bank, as well as its being situated closely to the water table, the excavation, in Reims, of the boulevard Dr. Henri-Henrot provided an excellent quality of preservation for perishable materials, including construction wood dating back to Antiquity. The material culture includes piles, planks, beams and staves, that were used in wall foundations, riverbank development, quays, dikes and formwork for gutters, basins, wells or pits. Few Gallo-Roman sites north of the Alps have yielded such large quantities of wooden remains and, even fewer presenting such an excellent a state of preservation. The method used here, known as dendrochronology, allows for the precise dating of wooden remains by examining the tree-rings. Seeking answers to chronological questions form the basis of this analysis, which seeks the comparison of the information collected with archaeological hypotheses. Of the 1,192 timbers collected and analyzed in context, 301 timber remains from 41 structures were dated. The dates obtained provide anchor points for the occupation history of the southern periphery of the ancient city of Reims. The first building was established around 13 BC and the last in 307 AD. During the first two centuries of our era, continuous building activity in this area was revealed through dendrochronological analysis. The 3rd c., however, demonstrated more punctual activity and only toward the beginning of the 4th c. did these activities resume with their prior intensity. The exceptional number of wooden elements recovered on site not only provides information on the state of the forest at that time, but also on its management, both of which may be related to changing environmental conditions and socio-economic processes. Furthermore, the wooden constructions, the applied techniques, as well as the extremely complex wooden assemblages documented through this approach provide an excellent account of carpentry and woodworking techniques in use during the Roman period. Thus, this study also provides a relevant and significant contribution to the history of these techniques.

Climate variations influenced the agricultural productivity, health risk, and conflict level of preindustrial societies. Discrimination between environmental and anthropogenic impacts on past civilizations, however, remains difficult because of the paucity of high-resolution paleoclimatic evidence. We present tree ring—based reconstructions of central European summer precipitation and temperature variability over the past 2500 years. Recent warming is unprecedented, but modern hydroclimatic variations may have at times been exceeded in magnitude and duration. Wet and warm summers occurred during periods of Roman and medieval prosperity. Increased climate variability from ∼250 to 600 C.E. coincided with the demise of the western Roman Empire and the turmoil of the Migration Period. Such historical data may provide a basis for counteracting the recent political and fiscal reluctance to mitigate projected climate change.

Societal upheaval occurred across Eurasia in the sixth and seventh centuries. Tree-ring reconstructions suggest a period of pronounced cooling during this time associated with several volcanic eruptions. Climatic changes during the first half of the Common Era have been suggested to play a role in societal reorganizations in Europe 1 , 2 and Asia 3 , 4 . In particular, the sixth century coincides with rising and falling civilizations 1 , 2 , 3 , 4 , 5 , 6 , pandemics 7 , 8 , human migration and political turmoil 8 , 9 , 10 , 11 , 12 , 13 . 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.  14 ), which was probably sustained by ocean and sea-ice feedbacks 15 , 16 , as well as a solar minimum 17 . 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 7 , 8 , transformation of the eastern Roman Empire and collapse of the Sasanian Empire 1 , 2 , 5 , movements out of the Asian steppe and Arabian Peninsula 8 , 11 , 12 , spread of Slavic-speaking peoples 9 , 10 and political upheavals in China 13 .

An important question for our understanding of Roman history is how the Empire's economy was structured, and how long-distance trading within and between its provinces was organised and achieved. Moreover, it is still unclear whether large construction timbers, for use in Italy, came from the widespread temperate forests north of the Alps and were then transported to the sparsely-wooded Mediterranean region in the south. Here, we present dendrochronological results from the archaeological excavation of an expensively decorated portico in the centre of Rome. The oak trees (Quercus sp.), providing twenty-four well-preserved planks in waterlogged ground, had been felled between 40 and 60 CE in the Jura Mountains of north-eastern France. It is most likely that the wood was transported to the Eternal City on the Saône and Rhône rivers and then across the Mediterranean Sea. This rare dendrochronological evidence from the capital of the Roman Empire gives fresh impetus to the ongoing debate on the likelihood of transporting timber over long distances within and between Roman provinces. This study reconstructs the administrative and logistic efforts required to transport high-quality construction timber from central Europe to Rome. It also highlights an advanced network of trade, and emphasises the enormous value of oak wood in Roman times.

To satisfy the increasing demand for wood in central Europe during medieval times, a new system of forest management was developed, one far superior to simple coppicing. The adoption of a sophisticated, Coppice-with-Standards (CWS) management practice created a two-storey forest structure that could provide fuelwood as well as construction timber. Here we present a dendrochronological study of actively managed CWS forests in northern Bavaria to detect the radial growth response to cyclical understorey harvesting in overstorey oaks ( Quercus sp.), so-called standards . All modern standards exhibit rapid growth releases every circa 30 years, most likely caused by regular understorey management. We further analyse tree-ring width patterns in 2120 oak timbers from historical buildings and archaeological excavations in southern Germany and north-eastern France, dating between 300 and 2015 CE, and succeeded in identifying CWS growth patterns throughout the medieval period. Several potential CWS standards even date to the first millennium CE, suggesting CWS management has been in practice long before its first mention in historical documents. Our dendrochronological approach should be expanded routinely to indentify the signature of past forest management practices in archaeological and historical oak wood.

The European Neolithization ~6000-4000 BC represents a pivotal change in human history when farming spread and the mobile style of life of the hunter-foragers was superseded by the agrarian culture. Permanent settlement structures and agricultural production systems required fundamental innovations in technology, subsistence, and resource utilization. Motivation, course, and timing of this transformation, however, remain debatable. Here we present annually resolved and absolutely dated dendroarchaeological information from four wooden water wells of the early Neolithic period that were excavated in Eastern Germany. A total of 151 oak timbers preserved in a waterlogged environment were dated between 5469 and 5098 BC and reveal unexpectedly refined carpentry skills. The recently discovered water wells enable for the first time a detailed insight into the earliest wood architecture and display the technological capabilities of humans ~7000 years ago. The timbered well constructions made of old oak trees feature an unopened tree-ring archive from which annually resolved and absolutely dated environmental data can be culled. Our results question the principle of continuous evolutionary development in prehistoric technology, and contradict the common belief that metal was necessary for complex timber constructions. Early Neolithic craftsmanship now suggests that the first farmers were also the first carpenters.

This study was supported by the projects “SustES - Adaptation strategies for sustainable ecosystem services and food security under adverse environmental conditions” (CZ.02.1.01/0.0/0.0/16_019/0000797) and “Výzkum proměn geografických procesů a vztahů v prostoru a čase (Progeo)” (MUNI/A/1356/2019).

The effects of climate change on Arctic ecosystems can range between various spatiotemporal scales and may include shifts in population distribution, community composition, plant phenology, primary productivity and species biodiversity. The growth rates and age structure of tundra vegetation as well as its response to temperature variation, however, remain poorly understood because high‐resolution data are limited in space and time. Anatomical and morphological stem characteristics were recorded to assess the growth behaviour and age structure of 871 dwarf shrubs from 10 species at 30 sites in coastal East Greenland at ˜70°N. Recruitment pulses were linked with changes in mean annual and summer temperature back to the 19th century, and a literature review was conducted to place our findings in a pan‐Arctic context. Low cambial activity translates into estimated average/maximum plant ages of 59/204 years, suggesting relatively small turnover rates and stable community composition. Decade‐long changes in the recruitment intensity were found to lag temperature variability by 2 and 6 years during warmer and colder periods, respectively (r = 0.85₁₉₆₁–₂₀₀₀ ₐₙd ₁₈₈₁–₁₉₂₀). Synthesis. Our results reveal a strong temperature dependency of Arctic dwarf shrub reproduction, a high vulnerability of circumpolar tundra ecosystems to climatic changes, and the ability of evaluating historical vegetation dynamics well beyond the northern treeline. The combined wood anatomical and plant ecological approach, considering insights from micro‐sections to community assemblages, indicates that model predictions of rapid tundra expansion (i.e. shrub growth) following intense warming might underestimate plant longevity and persistence but overestimate the sensitivity and reaction time of Arctic vegetation.

The new IntCal20 radiocarbon record continues decades of successful practice by employing one calibration curve as an approximation for different regions across the hemisphere. Here we investigate three radiocarbon time-series of archaeological and historical importance from the Mediterranean-Anatolian region, which indicate, or may include, offsets from IntCal20 (~0–22 14 C years). While modest, these differences are critical for our precise understanding of historical and environmental events across the Mediterranean Basin and Near East. Offsets towards older radiocarbon ages in Mediterranean-Anatolian wood can be explained by a divergence between high-resolution radiocarbon dates from the recent generation of accelerator mass spectrometry (AMS) versus dates from previous technologies, such as low-level gas proportional counting (LLGPC) and liquid scintillation spectrometry (LSS). However, another reason is likely differing growing season lengths and timings, which would affect the seasonal cycle of atmospheric radiocarbon concentrations recorded in different geographic zones. Understanding and correcting these offsets is key to the well-defined calendar placement of a Middle Bronze Age tree-ring chronology. This in turn resolves long-standing debate over Mesopotamian chronology in the earlier second millennium BCE. Last but not least, accurate dating is needed for any further assessment of the societal and environmental impact of the Thera/Santorini volcanic eruption.