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Central Europe has experienced a sequence of unprecedented summer droughts since 2015, which had considerable effects on the functioning and productivity of natural and agricultural systems. Placing these recent extremes in a long-term context of natural climate variability is, however, constrained by the limited length of observational records. Here, we use tree-ring stable oxygen and carbon isotopes to develop annually resolved reconstructions of growing season temperature and summer moisture variability for central Europe during the past 2000 years. Both records are independently interpolated across the southern Czech Republic and northeastern Austria to produce explicit estimates of the optimum agroclimatic zones, based on modern references of climatic forcing. Historical documentation of agricultural productivity and climate variability since 1090 CE provides strong quantitative verification of our new reconstructions. Our isotope records not only contain clear expressions of the medieval (920-1000 CE) and Renaissance (early sixteenth century) droughts, but also the relative influence of temperature and moisture on hydroclimatic conditions during the first millennium (including previously reported pluvials during the early third, fifth, and seventh centuries of the Common Era). We conclude that Czech agricultural production has experienced significant extremes over the past 2000 years, which includes periods for which there are no modern analogs. [ABSTRACT FROM AUTHOR]

Contextualising anthropogenic warming and investigating linkages between past climate variability and human history require high-resolution temperature reconstructions that extend before the period of instrumental measurements. Here, we present maximum latewood density (MXD) measurements of 534 living and relict Pinus uncinata trees from undisturbed upper treeline ecotones in the Spanish central Pyrenees. Spanning the period 1119–2020 CE continuously, our new MXD composite chronology correlates significantly with gridded May–September mean temperatures over the western Mediterranean region (r = 0.76; p ≤ 0.001; 1950–2020 CE). Based on an integrative ensemble approach, our reconstruction reveals unprecedented summer warming since 2003 CE. The coldest and warmest reconstructed temperature anomalies are −3.4 (±1.4) °C in 1258 and 2.6 (±2.2) °C in 2017 (relative to 1961–90). Abrupt summer cooling of −1.5 (±1.0) °C was found after 20 large volcanic eruptions since medieval times. Comparison of our summer temperature reconstruction with newly compiled historical evidence from the Iberian Peninsula suggests a lack of military conflict during or following exceptionally hot or cold summers, as well as a general tendency towards less warfare and more stable wheat prices during warmer periods. Our study demonstrates the importance of updating and refining annually resolved and absolutely dated climate reconstructions to place recent trends and extremes of anthropogenic warming in a long-term context of natural temperature variability, and to better understand how past climate and environmental changes affected ecological and societal systems. [Display omitted] • A total 534 MXD samples from the Pyrenees cover the period 1119–2020 CE continuously. • An integrative ensemble approach was used to improve our highly replicated MXD record. • Recent warming over the western Mediterranean is unprecedented since medieval times. • Abrupt summer cooling of −1.5 °C in the Pyrenees followed large volcanic eruptions. • Less warfare and stable wheat prices in Iberia coincide with periods of warmer climate. [ABSTRACT FROM AUTHOR]

A steep decline in the quality and quantity of available climate proxy records before medieval times challenges any comparison of reconstructed temperature and hydroclimate trends and extremes between the first and second half of the Common Era. Understanding of the physical causes, ecological responses and societal consequences of past climatic changes, however, demands highly-resolved, spatially-explicit, seasonally-defined and absolutely-dated archives over the entire period in question. Continuous efforts to improve existing proxy records and reconstruction methods and to develop new ones, as well as clear communication of all uncertainties (within and beyond academia) must be central tasks for the paleoclimate community. [ABSTRACT FROM AUTHOR]

Although tree-ring stable carbon (δ13C) and oxygen (δ18O) isotopes are increasingly used for climate reconstructions, it remains unclear whether isotopic ratios from the two chemical elements and different tree species exhibit age-related trends that require removal prior to any paleoclimatic interpretation. Here, we present 2,355 δ13C and 2,237 δ18O decadal measurements of living and relict Scots pines (Pinus sylvestris L.) from northern Fennoscandia to investigate the occurrence of isotope-specific age trends at both the individual tree and chronology level between 941 and 2010 CE, together with total-ring width and maximum density data. We show that δ13C values increase by ∼0.035‰ per 10 years of tree age, and therefore require detrending, which is not the case for δ18O that only contains minor changes related to age. This study provides independent evidence for the unique paleoclimatic value of stable δ18O isotopic ratios from the cellulose of living and relict pine wood to reconstruct high-to low-frequency climate variability. Conversely, caution is advised when information from diverse tree-ring parameters, species and regions is combined in multi-proxy climate reconstructions. [ABSTRACT FROM AUTHOR]

Tree-ring chronologies form the backbone of high-resolution palaeoclimatology. However, their number declines drastically prior to medieval times, and only a few such records worldwide extend back to the mid-Holocene. Here, we present a collection of more than 400 subfossil yew (Taxus baccata L.) trees excavated from near sea-level peat-rich sediments in the Fenland region of eastern England. The well-preserved yew trunks are between two and eight metres long, often exhibit adventitious root layers, and contain up to 400 rings of highly irregular growth. Combined dendrochronological and radiocarbon dating resulted in two tree-ring width chronologies that comprise 36 and 32 trees, span 413 and 418 years, exhibit mean inter-series correlations (Rbar) of 0.50 and 0.51, and were provisionally dated to 5225−4813 (±4) and 4612−4195 (±6) years cal BP. Together with a total of 63 radiocarbon dates (14C), our subfossil tree-ring evidence suggests that yew establishment (or onset of preservation) began ∼5250 years cal BP and resulted in extensive climax forests between 5200 and 4200 years cal BP. A first stage of yew decline ∼4800−4600 years cal BP was possibly caused by oxygen deprivation from soil wetting, whereas yew disappearance ∼4200 years cal BP is suggested to have been triggered by marine inundation as a consequence of rapid sea-level rise. Both phases of yew decline in eastern England coincide with marked reductions in subfossil oak and pine from peatbogs in Ireland, Germany and the Netherlands. Our results emphasise the potential to develop a dendrochronological network in coastal England for better understanding of larger-scale climate and environmental changes during the mid-Holocene, including the still debated 4.2 ka climate event. Moreover, we expect our subfossil yew chronologies to facilitate the dating of local archaeological remains, refine sea-level reconstructions around the British Isles, and contribute to the international radiocarbon calibration curve IntCal. [Display omitted] • We present >400 subfossil yew (Taxus baccata) trees from eastern England. • Dendrochronological and radiocarbon dating were combined for chronology development. • Two 400-year-long tree-ring chronologies date between 5200 and 4200 years cal BP. • Mid-Holocene woodlands in eastern England were dominated by yew until ∼4.2ka ago. • We hypothesise that yew disappearance around 4.2ka was related to rapid sea-level rise. [ABSTRACT FROM AUTHOR]