Antarctica's ice shelves modulate the grounded ice flow, and weakening of ice shelves due to climate forcing will decrease their ‘buttressing’ effect, causing a response in the grounded ice. While the processes governing ice-shelf weakening are complex, uncertainties in the response of the grounded ice sheet are also difficult to assess. The Antarctic BUttressing Model Intercomparison Project (ABUMIP) compares ice-sheet model responses to decrease in buttressing by investigating the ‘end-member’ scenario of total and sustained loss of ice shelves. Although unrealistic, this scenario enables gauging the sensitivity of an ensemble of 15 ice-sheet models to a total loss of buttressing, hence exhibiting the full potential of marine ice-sheet instability. All models predict that this scenario leads to multi-metre (1–12 m) sea-level rise over 500 years from present day. West Antarctic ice sheet collapse alone leads to a 1.91–5.08 m sea-level rise due to the marine ice-sheet instability. Mass loss rates are a strong function of the sliding/friction law, with plastic laws cause a further destabilization of the Aurora and Wilkes Subglacial Basins, East Antarctica. Improvements to marine ice-sheet models have greatly reduced variability between modelled ice-sheet responses to extreme ice-shelf loss, e.g. compared to the SeaRISE assessments.

Radiocarbon (14C) ages cannot provide absolutely dated chronologies for archaeological or paleoenvironmental studies directly but must be converted to calendar age equivalents using a calibration curve compensating for fluctuations in atmospheric 14C concentration. Although calibration curves are constructed from independently dated archives, they invariably require revision as new data become available and our understanding of the Earth system improves. In this volume the international 14C calibration curves for both the Northern and Southern Hemispheres, as well as for the ocean surface layer, have been updated to include a wealth of new data and extended to 55,000 cal BP. Based on tree rings, IntCal20 now extends as a fully atmospheric record to ca. 13,900 cal BP. For the older part of the timescale, IntCal20 comprises statistically integrated evidence from floating tree-ring chronologies, lacustrine and marine sediments, speleothems, and corals. We utilized improved evaluation of the timescales and location variable 14C offsets from the atmosphere (reservoir age, dead carbon fraction) for each dataset. New statistical methods have refined the structure of the calibration curves while maintaining a robust treatment of uncertainties in the 14C ages, the calendar ages and other corrections. The inclusion of modeled marine reservoir ages derived from a three-dimensional ocean circulation model has allowed us to apply more appropriate reservoir corrections to the marine 14C data rather than the previous use of constant regional offsets from the atmosphere. Here we provide an overview of the new and revised datasets and the associated methods used for the construction of the IntCal20 curve and explore potential regional offsets for tree-ring data. We discuss the main differences with respect to the previous calibration curve, IntCal13, and some of the implications for archaeology and geosciences ranging from the recent past to the time of the extinction of the Neanderthals.

Crocodilians are distributed widely through the tropics and subtropics, and several species pose a substantial threat to human life. This has important implications for human safety and crocodilian conservation. Understanding the drivers of crocodilian attacks on people could help minimize future attacks and inform conflict management. Crocodilian attacks follow a seasonal pattern in many regions, but there has been limited analysis of the relationship between attack occurrence and fine-scale contemporaneous environmental conditions. We use methods from environmental niche modelling to explore the relationships between attacks on people and abiotic predictors at a daily temporal resolution for the Nile crocodile Crocodylus niloticus in South Africa and Eswatini (formerly Swaziland), and the American alligator Alligator mississippiensis in Florida, USA. Our results indicate that ambient daily temperature is the most important abiotic temporal predictor of attack occurrence for both species, with attack likelihood increasing markedly when mean daily temperatures exceed 18 °C and peaking at 28 °C. It is likely that this relationship is explained partially by human propensity to spend time in and around water in warmer weather but also by the effect of temperature on crocodilian hunting behaviour and physiology, especially the ability to digest food. We discuss the potential of our findings to contribute to the management of crocodilians, with benefits for both human safety and conservation, and the application of environmental niche modelling for understanding human–wildlife conflicts involving both ectotherms and endotherms.

Immigration is highly salient for voters in Europe and the USA and has generated considerable academic debate about the causes of preferences over immigration. This debate centers around the relative influences of sociotropic or personal economic considerations, as well as noneconomic threats. We provide a test of the competing egocentric, sociotropic, and noneconomic paradigms using a novel constrained preference experiment in which respondents are asked to trade off preferred reductions in immigration levels with realistic estimates of the personal or societal costs associated with those reductions. This survey experiment, performed on a national sample of British YouGov panelists, allows us to measure the price-elasticity of the publicʼs preferences with regard to levels of European and non-European immigration. Respondents were willing to admit more immigrants when restriction carries economic costs, with egocentric considerations as important as sociotropic ones. People who voted for the UK to Leave the European Union in the 2016 referendum are less price-elastic than those voting Remain, indicating that noneconomic concerns are also important.1

The history of maize (Zea mays L.) in the eastern Woodlands remains an important study topic. As currently understood, these histories appear to vary regionally and include scenarios positing an early introduction and an increase in use over hundreds of, if not a thousand, years. In this article, we address the history of maize in the American Bottom region of Illinois and its importance in the development of regional Mississippian societies, specifically in the Cahokian polity located in the central Mississippi River valley. We present new lines of evidence that confirm subsistence-level maize use at Cahokia was introduced rather abruptly at about AD 900 and increased rapidly over the following centuries. Directly dated archaeobotanical maize remains, human and dog skeletal carbon isotope values, and a revised interpretation of the archaeological record support this interpretation. Our results suggest that population increases and the nucleation associated with Cahokia were facilitated by the newly introduced practices of maize cultivation and consumption. Maize should be recognized as having had a key role in providing subsistence security that—combined with social, political, and religious changes—fueled the emergence of Cahokia in AD 1050.