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Peer reviewed: True, Funder: Big Questions Institute, Annually resolved measurements of the radiocarbon content in tree-rings have revealed rare sharp rises in carbon-14 production. These ‘Miyake events’ are likely produced by rare increases in cosmic radiation from the Sun or other energetic astrophysical sources. The radiocarbon produced is not only circulated through the Earth’s atmosphere and oceans, but also absorbed by the biosphere and locked in the annual growth rings of trees. To interpret high-resolution tree-ring radiocarbon measurements therefore necessitates modelling the entire global carbon cycle. Here, we introduce ‘ ticktack ’ ( https://github.com/SharmaLlama/ticktack/ ), the first open-source Python package that connects box models of the carbon cycle with modern Bayesian inference tools. We use this to analyse all public annual 14 C tree data, and infer posterior parameters for all six known Miyake events. They do not show a consistent relationship to the solar cycle, and several display extended durations that challenge either astrophysical or geophysical models.

Transatlantic exploration took place centuries before the crossing of Columbus. Physical evidence for early European presence in the Americas can be found in Newfoundland, Canada1,2. However, it has thus far not been possible to determine when this activity took place3–5. Here we provide evidence that the Vikings were present in Newfoundland in ad 1021. We overcome the imprecision of previous age estimates by making use of the cosmic-ray-induced upsurge in atmospheric radiocarbon concentrations in ad 993 (ref. 6). Our new date lays down a marker for European cognisance of the Americas, and represents the first known point at which humans encircled the globe. It also provides a definitive tie point for future research into the initial consequences of transatlantic activity, such as the transference of knowledge, and the potential exchange of genetic information, biota and pathologies7,8., Precise dating of wooden artefacts at a Norse settlement in Newfoundland establishes that the Norse were in the Americas in ad 1021.

Carbonyl sulfide (COS) is used as a tracer for gross primary production (GPP) of terrestrial ecosystems and stomatal conductance of leaves. At present, sources and sinks of COS have not been fully assessed, as proven by the poor agreement between the modelled global budget and the most recent measurements. This uncertainty limits both the existing and potential future applications of COS. To understand sources and sinks of COS, the atmospheric station in Lutjewad (53°24’N, 6°21’E, 1m a.s.l.) performs continuous in situ mole fraction profile measurements. Nighttime COS fluxes of -3.0 ± 2.6 pmol m-2 s-1 were determined using the radon-tracer correlation approach. In three occasions between 2014 and 2018, COS enhancements ranging between 100 and 1000 ppt were measured in Lutjewad at 7, 40 and 60 meters above ground level. To identify the sources of these enhancements, both discrete and in situ samples were collected in the province of Groningen to be analysed with a quantum cascade laser spectrometer (QCLS). Several COS sources were identified, such as biodigesters, sugar production facilities and silicon carbide production facilities. These sources were added to the available databases, at a 0.1°x0.1° resolution. To simulate the initial dispersion, they were assumed to spread latitudinally and longitudinally over grids of 0.5°x0.5° width, as bidimensional Gaussian distributions. The updated databases were then combined with a Stochastic Time-Inverted Lagrangian Transport (STILT) model to check the influence of these sources on the Lutjewad measurements. Current results suggest a strong influence on the mole fraction of COS related to air parcels transported from known industrial sources, in particular from the Antwerp (51.2° N, 4.4° E) and Rotterdam (51.9° N, 4.5° E) regions. However, a mismatch still persists and preliminary results suggest that a local influence could explain the gap between modelled and measured COS concentrations. Possibly, COS emissions from these sources fluctuate according to different factors, such as the production rate of a specific facility or particular events. On the other hand, it is also possible that the enhancements in Lutjewad could be explained by scaling up the results to regional, national or international levels, adding similar facilities to the current databases. Nonetheless, these results could provide a useful insight about new sources of COS that could contribute to a more precise assessment of the global budget of this gas species.

The Tierra Blanca Joven (TBJ) eruption from Ilopango volcano deposited thick ash over much of El Salvador when it was inhabited by the Maya, and rendered all areas within at least 80 km of the volcano uninhabitable for years to decades after the eruption. Nonetheless, the more widespread environmental and climatic impacts of this large eruption are not well known because the eruption magnitude and date are not well constrained. In this multifaceted study we have resolved the date of the eruption to 431 ± 2 CE by identifying the ash layer in a well-dated, high-resolution Greenland ice-core record that is >7,000 km from Ilopango; and calculated that between 37 and 82 km3 of magma was dispersed from an eruption coignimbrite column that rose to ∼45 km by modeling the deposit thickness using state-of-the-art tephra dispersal methods. Sulfate records from an array of ice cores suggest stratospheric injection of 14 ± 2 Tg S associated with the TBJ eruption, exceeding those of the historic eruption of Pinatubo in 1991. Based on these estimates it is likely that the TBJ eruption produced a cooling of around 0.5 °C for a few years after the eruption. The modeled dispersal and higher sulfate concentrations recorded in Antarctic ice cores imply that the cooling would have been more pronounced in the Southern Hemisphere. The new date confirms the eruption occurred within the Early Classic phase when Maya expanded across Central America., Fieldwork in El Salvador was funded by a grant awarded to G.A.-D. (CONACYT-CB Grant 240447), and we acknowledge logistical support from the following institutions in El Salvador: Ministerio del Medio Ambiente y Recursos Naturales (MARN), Museo Nacional de Arqueología (MUNA), Universidad de El Salvador, and Policía Nacional Civil. V.C.S. and I.S.-P. acknowledge funding from the Natural Environment Research Council (NERC; Grant NE/5009035/1). A.C. acknowledges the Ministero dell’Istruzione dell’Università e della Ricerca project Ash-RESILIENCE. A.S. and M.W.D. acknowledge funding from the European Research Council (ERC) (ECHOES, Grant 714679). M.S. acknowledges funding from the ERC European Union’s Horizon 2020 research and innovation programme (Grant 820047). D.P. acknowledges support from Juan de la Cierva Grant IJCI-2016- 30482. The collection and analysis of the TUNU2013 core was supported by an NSF Division of Polar Programs Grant 1204176 awarded to J.R.M. We thank Walter Hernandez (MARN) and Hugo Díaz Chávez (MUNA) for assistance in the field, Stephen Harris (Department of Plant Sciences, University of Oxford) for identifying the species of the tree that we radiocarbon dated, and Ian Cartwright (School of Archaeology, University of Oxford) for photographing the cross-section of the tree

The Centre for Isotope Research (CIO) at the University of Groningen has operated a radiocarbon (14C) dating laboratory for almost 70 years. In 2017, the CIO received a major upgrade, which involved the relocation of the laboratory to new purpose-built premises, and the installation of a MICADAS accelerator mass spectrometer. This period of transition provides an opportunity to update the laboratory’s routine procedures. This article addresses all of the processes and quality checks the CIO has in place for registering, tracking and pretreating samples for radiocarbon dating. Complementary updates relating to radioisotope measurement and uncertainty propagation will be provided in other forthcoming publications. Here, the intention is to relay all the practical information regarding the chemical preparation of samples, and to provide a concise explanation as to why each step is deemed necessary.

Information about the global climate, the carbon cycle, changes in solar activity, and a number of other atmospheric processes are preserved in the carbon-14 and the beryllium-10 records. However, these isotope datasets are large and cumbersome to work with. We have designed a self-contained, easy-to-use application that allows for more efficient analysis of different periods and patterns of interest. For several applications in atmospheric modelling, a pre-processing stage is applied to the isotope datasets in order to interpolate the data and mitigate their low temporal resolution. In CHRONOscope, we included linear and non-linear methods of interpolation with interactive parameter optimization. The resultant interpolated data can be extracted for further use. The main functionalities of CHRONOscope include the importation and superimposition of external data, quick navigation through the data with the use of markers, expression of the carbon-14 results in both Δ14C and yr BP form, separation of the data by source, and the visualization of associated error bars. We make this free software available in standalone applications for both Windows and Mac operating systems.

Carbonyl sulfide (COS) is the most abundant reduced sulfur gas in the atmosphere and is used as a tracer for gross primary production (GPP) of terrestrial ecosystems and stomatal conductance of leaves. At present, its usefulness is limited by the uncertainties in the estimation of its sources and sinks. In this study, we aim to understand the COS budget using atmospheric COS enhancements at the Lutjewad tower (53°24’N, 6°21’E, 1m a.s.l.) and atmospheric measurements of COS in the province of Groningen using a mobile van. We infer the sources and sinks of COS using continuous in situ mole fraction profile measurements of COS at Lutjewad. We determined the nighttime COS fluxes to be -3.0 ± 2.6 pmol m-2 s-1 using the radon-tracer correlation approach. We observed enhancements of COS mole fractions on the order of 100 ppt (lasting a few days) to 1000 ppt (lasting a few hours) at three occasions. To quantify potentially unidentified COS sources, we have made additional measurements by collecting air flasks that were analyzed later in the laboratory and with a continuous quantum cascade laser spectrometer. We have identified multiple COS sources, such as biodigesters, sugar production facilities and silicon carbide production facilities. Furthermore, we simulate the Lutjewad COS mole fractions in a Lagrangian model framework to quantitatively understand the COS sources and sinks. These results are useful for improving our understanding of the sources and sinks of COS, contributing to the use of COS as a tracer for GPP.

Extreme cosmic radiation events occurred in the years 774/5 and 993/4 CE, as revealed by anomalies in the concentration of radiocarbon in known-age tree-rings. Most hypotheses point towards intense solar storms as the cause for these events, although little direct experimental support for this claim has thus far come to light. In this study, we perform very high-precision accelerator mass spectrometry (AMS) measurements on dendrochronological tree-rings spanning the years of the events of interest, as well as the Carrington Event of 1859 CE, which is recognized as an extreme solar storm even though it did not generate an anomalous radiocarbon signature. Our data, comprising 169 new and previously published measurements, appear to delineate the modulation of radiocarbon production due to the Schwabe (11-year) solar cycle. Moreover, they suggest that all three events occurred around the maximum of the solar cycle, adding experimental support for a common solar origin.

On the basis of epidemiological studies it has been proposed that cannabis use plays a causal role in the abuse of highly addictive drugs (Gateway Hypothesis). However, epidemiological studies are intrinsically unable to provide evidence of causality. Experimental studies can provide this evidence but they are feasible only in animal models and to date such evidence is lacking. In view of the importance of genetic factors in drug abuse, we investigated the influence of adolescent cannabis exposure on adult heroin reinforcement in two inbred rat strains differentially vulnerable to drugs of abuse, addiction prone Lewis (LEW) and addiction resistant Fischer 344 (F344) strains. Male LEW and F344 rats aged six weeks were exposed to increasing Δ9-tetrahydrocannabinol (THC) doses, twice a day for 3 days (2, 4, 8 mg/kg, i.p.). At adulthood they were allowed to self-administer heroin (0.025 mg/kg) under both Fixed- (FR) and Progressive- (PR) ratio schedules of responding. Following extinction, responding was reinstated by drug-cues and/or by heroin priming. THC pre-exposure increased responding for heroin and heroin intake under FR-3 and FR-5 as well as PR protocols and increased breaking point in PR schedules in LEW but not F344 rats. Drug cues and heroin priming reinstated responding in LEW and F344, but THC pre-exposure increased reinstatement by priming in LEW rats and by cues in F344 rats. These observations show that in genetically predisposed individuals, adolescent cannabis exposure increases heroin reinforcing properties, thus providing a mechanism for a causal role of adolescent cannabis use in heroin abuse.

Significance The problem with radiocarbon dating is that its resolution is only centennial or, at the very best, decadal. Thus, the method is incapable of resolving many historical problems. Here, we use recent developments in atmospheric science to date the construction of a renowned archaeological site to the exact year, in fact, to the exact season. Such precision opens up new possibilities for the broader study of human history. Achieving dates on an annual scale will offer the potential for new assessments to be made of considerable archaeological significance., Inadequate resolution is the principal limitation of radiocarbon dating. However, recent work has shown that exact-year precision is attainable if use can be made of past increases in atmospheric radiocarbon concentration or so-called Miyake events. Here, this nascent method is applied to an archaeological site of previously unknown age. We locate the distinctive radiocarbon signal of the year 775 common era (CE) in wood from the base of the Uyghur monument of Por-Bajin in Russia. Our analysis shows that the construction of Por-Bajin started in the summer of 777 CE, a foundation date that resolves decades of debate and allows the origin and purpose of the building to be established.

Extreme bursts of radiation from space result in rapid increases in the concentration of radiocarbon in the atmosphere. Such rises, known as Miyake Events, can be detected through the measurement of radiocarbon in dendrochronological archives. The identification of Miyake Events is important because radiation impacts of this magnitude pose an existential threat to satellite communications and aeronautical avionics and may even be detrimental to human health. However, at present, radiocarbon measurements on tree-ring archives are generally only available at decadal resolution, which smooths out the effect of a possible radiation burst. The Miyake Events discovered so far, in tree-rings from the years 3372-3371 BCE, 774–775 CE, and 993–994 CE, have essentially been found by chance, but there may be more. In this paper, we use signal processing techniques, in particular COSFIRE, to train filters with data on annual changes in radiocarbon ( $\Delta ^{14}\text{C}$ ) around those dates. Then, we evaluate the trained filters and attempt to detect similar Miyake Events in the past. The method that we propose is promising, since it identifies the known Miyake Events at a relatively low false positive rate. Using the findings of this paper, we propose a list of 26 calendar years that our system persistently indicates are Miyake Event-like. We are currently examining a short-list of five of the newly identified dates and intend to perform single-year radiocarbon measurements over them. Signal processing techniques, such as COSFIRE filters, can be used as guidance tools since they are able to identify similar patterns of interest, even if they vary in time or in amplitude.