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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.

In many parts of the world, especially in the temperate regions of Europe and North-America, accelerated tree growth rates have been observed over the last decades. This widespread phenomenon is presumably caused by a combination of factors like atmospheric fertilization or changes in forest structure and/or management. If not properly acknowledged in the calibration of tree-ring based climate reconstructions, considerable bias concerning amplitudes and trends of reconstructed climatic parameters might emerge or low frequency information is lost. Here we present a simple but effective, data-driven approach to remove the recent non-climatic growth increase in tree-ring data. Accounting for the no-analogue calibration problem, a new hydroclimatic reconstruction for northern-central Europe revealed considerably drier conditions during the medieval climate anomaly (MCA) compared with standard reconstruction methods and other existing reconstructions. This demonstrates the necessity to account for fertilization effects in modern tree-ring data from affected regions before calibrating reconstruction models, to avoid biased results.

The African baobab, Adansonia digitata L., has great paleoclimatological potential because of its wide distributional range and millennial length life span. However, dendroclimatological approaches are hampered by dating uncertainties due to its unique, parenchyma-dominated stem anatomy. Here, securely dated time series of annual wood increment growth and intra-ring stable isotopes of carbon and oxygen of cellulose for a baobab tree from Oman covering 1941 to 2005 were established and tested for relationships to hydroclimate variability. Precise dating with the atomic bomb peak (ABP) using highly resolved 14C measurements confirmed the annual character of the baobab's growth rings. F14C values of tree-ring cellulose were found up to 8.8 % lower than in the corresponding atmospheric CO2 for the period around the ABP, which in conjunction with a considerable autocorrelation of the δ13C series points to the incorporation of previous year's carbon contributing to the average age of intra-ring wood samples. F14C of terminal parenchyma bands, marking the tree-ring boundaries, were found to be considerably younger than their corresponding tree ring, indicating that parenchyma tissue is alive for many years, probably undergoing cell division and structural reorganization and contributing to secondary growth. In contrast to the δ13C time series, no significant autocorrelation was found in the δ18O series of tree-ring cellulose despite the enormous water storage potential of this stem-succulent tree species. Year-to-year variability in tree-ring width and stable isotope ratios revealed radial stem growth and the geochemistry of wood cellulose are influenced by fluctuations in the hydroclimate. In particular, δ18O was found to be a good climate proxy, followed by tree-ring width and δ13C. Tree-ring width and intra-ringδ18Omin correlated well with each other and with precipitation amount for the period from pre-monsoon May to the end of the monsoon season in September/October. Intra-annual stable isotope courses were found to be rather similar for both δ13C and δ18O. Years with particularly low monsoon rain were reflected by increased stable isotope values in the mid-section of intra-annual courses. Distinct patterns with low subseasonal isotope values seem indicative for years with heavy rainfall events from pre-monsoonal cyclones. Rain events from post-monsoonal cyclones may also be recorded; however, only 2 years of observation prevented a more conclusive evaluation.

Tree ring–based temperature reconstructions form the scientific backbone of the current global change debate. Although some European records extend into medieval times, high-resolution, long-term, regional-scale paleoclimatic evidence is missing for the eastern part of the continent. Here we compile 545 samples of living trees and historical timbers from the greater Tatra region to reconstruct interannual to centennial-long variations in Eastern European May–June temperature back to 1040 AD. Recent anthropogenic warming exceeds the range of past natural climate variability. Increased plague outbreaks and political conflicts, as well as decreased settlement activities, coincided with temperature depressions. The Black Death in the mid-14th century, the Thirty Years War in the early 17th century, and the French Invasion of Russia in the early 19th century all occurred during the coldest episodes of the last millennium. A comparison with summer temperature reconstructions from Scandinavia, the Alps, and the Pyrenees emphasizes the seasonal and spatial specificity of our results, questioning those large-scale reconstructions that simply average individual sites.

The carved wooden object uncovered from the Shigir peat bog in the Sverdlovsk region towards the end of the nineteenth century remains one of the oldest, known examples of monumental anthropomorphic sculpture from anywhere in the world. Recent application of new analytical techniques has led to the discovery of new imagery on its surface, and has pushed the date of the piece back to the earliest Holocene. The results of these recent analyses are placed here in the context of local and extra-local traditions of comparable prehistoric art. This discussion highlights the unique nature of the find and its significance for appreciating the complex symbolic world of Early Holocene hunter-gatherers.

Forest decline played a pivotal role in motivating Europe's political focus on sustainability around 35 years ago. Silver fir ( Abies alba ) exhibited a particularly severe dieback in the mid-1970s, but disentangling biotic from abiotic drivers remained challenging because both spatial and temporal data were lacking. Here, we analyze 14 136 samples from living trees and historical timbers, together with 356 pollen records, to evaluate recent fir growth from a continent-wide and Holocene-long perspective. Land use and climate change influenced forest growth over the past millennium, whereas anthropogenic emissions of acidic sulfates and nitrates became important after about 1850. Pollution control since the 1980s, together with a warmer but not drier climate, has facilitated an unprecedented surge in productivity across Central European fir stands. Restricted fir distribution prior to the Mesolithic and again in the Modern Era, separated by a peak in abundance during the Bronze Age, is indicative of the long-term interplay of changing temperatures, shifts in the hydrological cycle, and human impacts that have shaped forest structure and productivity.

Two tree-ring series, one from a high-latitude pine tree (located in northern Scandinavia) and one from a mid-latitude oak tree (located in eastern Germany) were analyzed for radiocarbon (14C) at annual resolution. The new records cover the calendar date ranges 290–460 AD and 382–486 AD, respectively, overlapping by 79 yr. The series show similar trends as IntCal13. However, some significant deviations around 400 AD are present with lower Δ14C (higher 14C ages). An average offset between the two new series and IntCal13 of about 20 years in conventional 14C age is observed. A latitudinal 14C offset between the tree sites in central and northern Europe, as would be expected due to the relatively large spatial distance, is not recorded, however. Periodic changes in the 14C records are resolved that can be attributed to the “11-year” solar cycle (Schwabe cycle) with cycle length from 9 to 11 years. The magnitude of changes in Δ14C due to the solar cycle is between 1.5 and 3‰. Since solar cyclicity is only partially synchronous between the two new series, reasons for asynchronicity are explored.

According to the Intergovernmental Panel on Climate Change (IPCC), all of Africa is very likely to warm up more than the global average during this century. Especially (semi-)arid regions are expected to experience particularly high warming and possibly catastrophic droughts. However, assessments of the impacts of climate change on these regions are currently impeded by a lack of transregional high temporal resolution proxy data for the African continent. Baobab trees are widely distributed in (semi-)arid Africa and can reach ages of up to 2000 years. This pilot study was aimed at investigating African baobabs, Adansonia spp., from a site in Botswana using multiple dendroclimatological methods. Increment cores from 16 individual baobabs growing on Kubu Island (20°53' S, 25°49' E), a granite pluton located in the Kalahari, were collected in June 2011 to test for annual growth and the species' utility for palaeoclimatic studies. Due to the particular wood fabric and relatively high water content, baobab increment cores were packed in air-tight opaque tubes and stored in a freezer to prevent drying and mould formation. The complicated wood anatomical structure was found to be analysed best using a microscope with incident UV light, allowing tree-ring boundaries to be distinguished. Nonetheless, potential differences in individual site conditions, as well as diverse tree ages, caused conventional dendrochronological crossdating to fail. Missing and false tree rings could be identified due to the strong relationship between tree-ring width and annual precipitation amount allowing the development of a preliminary 50 year-long baobab chronology (1960-2009). Subsequently, stable carbon and oxygen isotope analyses revealed significant correlations of Δ¹³C and δ¹⁸O of tree rings with climate data. Year-to-year isotope variability and trends were found to be in good agreement with established models of fractionation. Intrinsic water-use efficiency has mainly increased over the study period (2-30%). Despite the demonstrated high potential of African baobabs as a valuable high-resolution climate archive, we conclude that more dendrochronological calibration studies are required at various sites in southern Africa. Furthermore, ecophysiological monitoring of climate and stable isotope signal transfer from the atmosphere, through soil and leaves into the tree rings is necessary to fully understand tree-ring formation and climate response of the African baobab. Laut Weltklimarat (Intergovernmental Panel on Climate Change, IPCC) wird Afrika sehr wahrscheinlich eine Erwärmung erfahren, die über dem globalen Mittel liegen wird. Speziell aride Gebiete sind durch eine hohe Erwärmung und mögliche katastrophale Dürren gefährdet. Den Einschätzungen der Auswirkungen des Klimawandels auf diese Regionen steht aber derzeit ein großer Mangel an überregionalen, zeitlich hochaufgelösten und präzise datierten Proxy-Datenreihen für den afrikanischen Kontinent entgegen. Baobabs sind im (semi-) ariden Afrika weit verbreitet und können bis zu 2000 Jahre alt werden. Das Ziel dieser Pilotstudie war es, Afrikanische Baobabs, Adansonia spp., von einem Standort in Botsuana mit verschiedenen dendrochronologischen Methoden zu untersuchen. Im Juni 2011 wurden 16 Baobabs auf Kubu Island (20°53' S, 25°49' E), einem Granitpluton in der Kalahari Botsuanas, Zuwachsbohrkerne entnommen, urn zu testen, ob es sich bei den Zuwachszonen der Baobabs um Jahrringe handelt und, um ihre Nutzbarkeit für Paläo-Klimastudien zu untersuchen. Aufgrund ihrer besonderen Holzstruktur und dem relativ hohen Wassergehalt wurden die Zuwachsbohrkerne in luftdichte, lichtundurchlässige Röhren verpackt und so schnell wie möglich eingefroren, um Austrocknung und Schimmelbildung zu verhindern. Die komplizierte Holzanatomie lässt sich am besten mit einem UV-Iicht-Mikroskop analysieren, das die Differenzierung der Jahrringgrenzen ermöglicht. Trotzdem fuhrten potentielle Standort- und Altersunterschiede dazu, dass die Proben nicht auf konventionelle Art kreuzdatiert werden konnten. Der stark ausgeprägte Zusammenhang zwischen Jahrringbreite und Jahresniederschlag ermöglichte es aber, fehlende und falsche Jahrringe zu identifizieren und so eine vorläufige 50 Jahre lange Baobab-Chronologie (1960—2009) zu erstellen. Die anschließende Analyse stabiler Kohlenstoff- und Sauerstoffisotope ergab signifikante Korrelationen von Δ¹³C und δ¹⁸O der Jahrringe mit Klimadaten. Die jährliche Isotopenvariabilität und die Trends der Isotope sind im Einklang mit anerkannten Fraktionierungs-Modellen. Die intrinsische Wassernutzungseffizienz hat sich über den Untersuchungszeitraum überwiegend verbessert (2-30%). Trotz des demonstrierten großen Potentials der Afrikanischen Baobabs als zukünftiges hoch-aufgelöstes Klimaarchiv kommen wir zu dem Schluss, dass es weiterer dendrochronologischer Kalibrierungsstudien an unterschiedlichen Standorten im südlichen Afrika bedarf. Darüber hinaus ist ein ökophysiologisches Monitoring des Transfers von Klimasignalen und stabilen Isotopen aus der Atmosphäre durch den Boden und die Blätter in die Jahrringe erforderlich, um die Jahrringbildung und die Klimareaktion der Afrikanischen Baobabs vollstandig zu verstehen.

Uncertainty related to the rate and magnitude of predicted anthropogenic climate change highlights the need to enhance our understanding of past natural fluctuations in the Earth's climate system. This task emphasizes the importance of high-resolution palaeoclimatic records that cover industrial and pre-industrial times. Annually resolved and absolutely dated tree-ring measurements are a key input for cross-disciplinary research. Ambiguity due to paucity of data, however, characterizes many tree-ring data analyses. By utilizing nearly 12 000 living and historical ring width series from European firAbies albaMill., we demonstrate how massive sample replication can generate robust estimates of past growth rates, which may help reduce methodological and statistical constraints associated with many traditional tree-ring studies.

The African baobab, Adansonia digitata L., has great paleoclimatological potential because of its wide distributional range and millennial length life span. However, dendroclimatological approaches are hampered by dating uncertainties due to its unique, parenchyma-dominated stem anatomy. Here, securely dated time series of annual wood increment growth and intra-ring stable isotopes of carbon and oxygen of cellulose for a baobab tree from Oman covering 1941 to 2005 were established and tested for relationships to hydroclimate variability. Precise dating with the atomic bomb peak (ABP) using highly resolved .sup.14 C measurements confirmed the annual character of the baobab's growth rings. F.sup.14 C values of tree-ring cellulose were found up to 8.8 % lower than in the corresponding atmospheric CO.sub.2 for the period around the ABP, which in conjunction with a considerable autocorrelation of the [delta].sup.13 C series points to the incorporation of previous year's carbon contributing to the average age of intra-ring wood samples. F.sup.14 C of terminal parenchyma bands, marking the tree-ring boundaries, were found to be considerably younger than their corresponding tree ring, indicating that parenchyma tissue is alive for many years, probably undergoing cell division and structural reorganization and contributing to secondary growth. In contrast to the [delta].sup.13 C time series, no significant autocorrelation was found in the [delta].sup.18 O series of tree-ring cellulose despite the enormous water storage potential of this stem-succulent tree species. Year-to-year variability in tree-ring width and stable isotope ratios revealed radial stem growth and the geochemistry of wood cellulose are influenced by fluctuations in the hydroclimate. In particular, [delta].sup.18 O was found to be a good climate proxy, followed by tree-ring width and [delta].sup.13 C. Tree-ring width and intra-ring [delta].sup.18 O.sub.min correlated well with each other and with precipitation amount for the period from pre-monsoon May to the end of the monsoon season in September/October. Intra-annual stable isotope courses were found to be rather similar for both [delta].sup.13 C and [delta].sup.18 O. Years with particularly low monsoon rain were reflected by increased stable isotope values in the mid-section of intra-annual courses. Distinct patterns with low subseasonal isotope values seem indicative for years with heavy rainfall events from pre-monsoonal cyclones. Rain events from post-monsoonal cyclones may also be recorded; however, only 2 years of observation prevented a more conclusive evaluation.