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This study aimed to investigate age-related injury incidence, severity, and burden over a 3-year period in U14 to U19 elite male soccer players in a German youth academy.Descriptive epidemiology study.Time-loss injuries of 166 unique players were prospectively documented and injury incidence, severity, and burden were calculated for each age group, body part, and type of injuries.A total of 562 time-loss injuries were recorded. Across all age groups (U14 to U19), injury incidence was 42.2 per squad season (ranging from 30.5 in the U19 to 67.7 in the U15), severity was 11.0 days lost (ranging from 8.0 in the U15 to 17.0 in the U17), and burden was 464.1 days lost per squad season (ranging from 304.9 in the U19 to 756.7 in the U14). The thigh, knee and ankle were the body parts with the highest injury incidence (9.2; 5.9; 5.9), severity (11.0; 16.0; 13.0), and burden (101.6; 94.9; 76.1). Cruciate ligament injuries had both the highest burden (164.4) and severity (137.0), and muscle injuries the highest incidence (11.0) of all types of injuries. U15 had the highest injury incidence (67.7) of all age groups. U14 and U17 had both the highest injury severity (15.0; 17.0) and burden (756.7; 618.8) of all age groups. Age-related patterns were observed for selected types of injuries such as muscle injuries, tendinopathy, bone-stress injury, and fractures.Injury incidence, severity, and burden substantially differed descriptively between age groups and clear age-related patterns for selected types of injuries were evident.

Model simulations of past and future Antarctic ice sheet (AIS) evolution depend on the applied climatic forcing. To model the present and future Antarctic ice sheet, several different forcings from regional climate models are available. It is therefore critical to understand the influence and the resulting model differences and uncertainties associated with the choice of present-day reference forcing. We apply present-day climatic forcings from regional models (RACMO2.3p2, MAR3.10, HIRHAM5 and COSMO-CLM2) combined with climate anomalies from a global climate model (HadGEM2-ES). With this setup, we investigate the future evolution of the AIS under the RCP2.6, RCP4.5 and RCP8.5 scenarios using the Parallel Ice Sheet Model (PISM). We find substantial differences in the future evolution of the AIS depending on the choice of the present-day reference field even under an extreme scenario such as RCP8.5. We discuss the influence of those forcing choices on the projected future AIS dynamics and sea-level contribution, considering a variety of ice sheet model parameterizations. With this analysis, we aim to gain a better understanding of the role of climate forcing choices and parameterization-induced uncertainties of sea-level rise projections.

Proxy-based reconstructions and climate model simulations of surface temperature trends during the Holocene disagree: While reconstructions show a cooling during the mid- and late Holocene, climate models show a continuous warming – a contradiction known as the Holocene temperature conundrum. Despite extensive research, the reason for the disagreement remains unclear. Both, missing processes in the models as well as biases in the proxies and the resulting reconstructions are possible sources of the conundrum. Here we compare our TransEBM v1.2 climate simulation as well as additional climate models of different complexity and Holocene temperature trends from the Temperature12k dataset (Kaufman et al., 2020b), with regards to model-data and model-model agreement. We show that models of all complexities disagree with mid-Holocene temperature trends in reconstructions and that this disagreement is almost independent of proxy and archive type. While, models show the highest agreement with summer temperature trends in reconstructions, our study shows that a trivial summer bias in proxies is not sufficient to explain the conundrum. Further effort to disentangle seasonal biases in proxies and the testing of potential misrepresentations in climate models, like anthropogenic land-use, in form of sensitivity experiments are needed to resolve the Holocene conundrum.

Projections of anthropogenic climate change suggest possible surface temperature increases similar to those during past major shifts of the mean climate like the Last Deglaciation. Such shifts do not only affect the mean but rather the full probability distributions of climatic variables such as temperature and precipitation. Changes to their distributions can thus be expected for the future as well and need to be constrained. To this end, we examine transient simulations of the Last Deglaciation from a hierarchy of climate models, ranging from an energy balance model to state-of-the-art Earth System Models. Besides the mean, we use the higher moments of variability – variance, skewness, and kurtosis – to characterize changes of the distribution. The analysis covers annual to millennial timescales and examines how patterns vary with timescale and region in response to warming. Furthermore, we evaluate how the changes of the distributions affect the occurrence of extremes. To analyze the influence of forcings on the distributions, we compare the patterns of the fully-forced simulations to those in sensitivity experiments that isolate the effects of individual forcings. In particular, the effect of volcanism is examined across the hierarchy, as well as changes in ice cover, freshwater input, CO2, and orbit. While large-scale global patterns can be found, there are significant regional differences as well as differences between simulations, relating for example to differences in the modelling of ice cover changes and freshwater input. Finally, we investigate whether climate model projections show the same trends with respect to the change in moments as those found in the deglacial simulations and thus whether the patterns found might hold for future climate.

Simulations of past and future Antarctic ice sheet (AIS) evolution depend, besides the intrinsic model specific uncertainties, on the applied climatic forcing. To model the past, present and future Antarctic Ice Sheet, a large set of different forcings from global and regional climate models, is available. For a more complete understanding of the modeled ice sheet dynamics, it is therefore critical to understand the influence and the resulting model differences and uncertainties associated with climate forcing choices. In this study we examine the impact of different climatic forcings onto the equilibrium state of the AIS for past and present-day conditions. We apply past (LGM, LIG, mid-Pliocene warm period) and present-day climatic forcings from regional (RACMO2.3p2, MAR3.10, HIRHAM5 and COSMO-CLM) and global (PMIP4 ensemble) climate models onto the Parallel Ice Sheet Model (PISM v.2.0). Further, we investigate the response of the total ice mass, its distribution and the grounding line dynamics of the modeled equilibrium ice sheet under varying ice sheet sensitivity parameterizations. With this analysis, we aim to gain a better understanding of AIS modelling uncertainties due to the applied climatic forcings and parameterizations, which will improve the assessment of modeled past and future ice-sheet evolution.

Much about the response of temperature variability to a change in the climate's mean state, as the one projected for the current century, remains uncertain. These uncertainties include spatiotemporal patterns, the magnitude, and, in some cases, even the sign. For the last Deglaciation, - the last change in global mean temperature of a similar degree to that expected in projections - variability analyses of climate model simulations and temperature proxies produce conflicting results. Here, we build a hierarchy of transient simulations covering the period since the Last Glacial Maximum about 26k years ago. We include a range of climate models, from conceptual to complex Earth System Models. The simulations cover a variety of temporal and spatial resolutions, parameterizations, and modeled processes. For annual to multi-millennial temporal as well as regional to global spatial scales, we compare variability patterns and power spectra and analyze how they relate to model properties and the background state of Earth's climate. This allows for the examination of regional temperature differences between low, middle, and high latitudes and at locations of available paleoclimate proxy records. For sets of sensitivity experiments, we investigate effects of changes to ice sheets, sea ice, and in volcanic, solar, greenhouse, and orbital forcing on modeled climate variability. Thus, our analysis provides insights into when and how models disagree with each other and with proxies, and what differences arise due to specific models, simulation setups, and boundary conditions. Based on these results, we can then gauge the degree of complexity which is required to reproduce past temperature variability and predict its changes in the future.

Modeled and observed temperature trends over the Holocene disagree. Proxy reconstructions suggest global cooling during the late Holocene. Model simulations, on the other hand, show a warming trend for the entire Holocene, a contradiction known as the Holocene temperature conundrum. A recent study by Bader et. al. (2020) introduced a new approach to the question by proposing the coexistence of a cooling and warming climate mode. While the warming mode is proposed to be related to changes in greenhouse gas concentrations, the physical process behind the cooling mode might be a change in the seasonal cycle of Arctic sea-ice. It’s unclear to what extent this process is responsible for the observed climate response. Depending on their strength and location these modes have strong implications for proxy data interpretation and location selection when calculating global mean temperatures. Here, we investigate if similar modes and temperature trends can be found in models of different complexity. Therefore, we use a 2D Energy Balance Model (EBM), with solar, volcanic, ice-sheet and greenhouse gas forcing, for transient simulations of the Holocene climate. We analyze these Holocene climate simulations in terms of global and regional temperature trends, modes and variability patterns. We conduct sensitivity tests to examine the influence of the forcings on those trends and modes. In particular, we are interested in the influence of volcanic eruptions on the Holocene climate. Furthermore, we compare our model results with temperature reconstructions and simulations from Earth System Models. Altogether, we comprehensively analyze Holocene climate as simulated by a conceptual EBM, a state-of-the-art Earth System Model and proxy reconstructions. The results provide insight into whether models of different complexity produce similar modes and trends and whether these occur due to climate forcing rather than internal processes of the earth system. Finally, we will provide a better understanding of Holocene cooling and warming and the interpretation of differences between Holocene temperature proxy reconstructions and climate model simulations. References: Bader, J., Jungclaus, J., Krivova, N. et al. Global temperature modes shed light on the Holocene temperature conundrum. Nat Commun 11, 4726 (2020). https://doi.org/10.1038/s41467-020-18478-6