Deforestation influences surface properties such as surface roughness, resulting in changes in the surface energy balance and surface temperature. Recent studies suggest that the biogeophysical ...effects are dominated by changing roughness, and it remains unclear whether this can be reconciled with earlier modeling studies that highlighted the importance of a reduction of evapotranspiration in the low latitudes and a reduction of net shortwave radiation at the surface in the high latitudes. To clarify this situation, we analyze the local effects of deforestation on surface energy balance and temperature in the MPI‐ESM climate model by performing three separate experiments: switching from forest to grass all surface properties, only surface albedo, and only surface roughness. We find that the locally induced changes in surface temperature are dominated by changes in surface roughness for the annual mean, the response of the diurnal amplitude, and the seasonal response to deforestation. For these three quantities, the results of the MPI‐ESM lie within the range of observation‐based data sets. Deforestation‐induced decreases in surface roughness contribute substantially to winter cooling in the boreal regions and to decreases in evapotranspiration in the tropics. By comparing the energy balance decompositions from the three experiments, the view that roughness changes dominate the biogeophysical consequences of deforestation can be reconciled with the earlier studies highlighting the relevance of evapotranspiration.
Key Points
Climate model simulations reveal that surface roughness dominates the local surface temperature change signal in most geographic regions
The study reconciles findings from studies focusing on changes in the surface energy balance and on changes in surface properties
Model outcomes are consistent with observed changes in surface temperature across annual, diurnal, and seasonal time scales
Online platforms not only serve to exchange information and goods but increasingly also service work provided by the self‐employed. The emergence of crowdsourcing of paid work has created a global ...market for online labour where services can be fully acquired and provided irrespective of location via platforms such as upwork.com or freelancer.com. Drawing on a content analysis of the websites of 44 globally operating platforms, this study has investigated the discursive construction of this new type of labour market. The findings show that platforms address the online workforce in different ways, for instance, as workers or freelancers. Contrary to their blanket characterisation as an anonymous crowd in previous academic debate, in most cases, online workers are forced to present themselves as talented experts to distinguish themselves from the mass of competitors. The control over online labour that these platforms exercise challenges existing conceptions of professionalism and self‐employment.
Historical changes in soil carbon associated with land-use change (LUC) result mainly from the changes in the quantity of litter inputs to the soil and the turnover of carbon in soils. We use a ...factor separation technique to assess how the input-driven and turnover-driven controls, as well as their synergies, have contributed to historical changes in soil carbon associated with LUC. We apply this approach to equilibrium simulations of present-day and pre-industrial land use performed using the dynamic global vegetation model JSBACH. Our results show that both the input-driven and turnover-driven changes generally contribute to a gain in soil carbon in afforested regions and a loss in deforested regions. However, in regions where grasslands have been converted to croplands, we find an input-driven loss that is partly offset by a turnover-driven gain, which stems from a decrease in the fire-related carbon losses. Omitting land management through crop and wood harvest substantially reduces the global losses through the input-driven changes. Our study thus suggests that the dominating control of soil carbon losses is via the input-driven changes, which are more directly accessible to human management than the turnover-driven ones.
An abdominal aortic aneurysm (AAA) is a balloon-like dilation of the aorta, which is potentially fatal in case of rupture. Computational finite element (FE) analysis is a promising approach to a more ...accurate and patient-specific rupture risk prediction. AAA wall strength and rupture potential index (RPI) calculation are implemented in our FE software. Static structural FE simulations are performed on n = 30 non-ruptured asymptomatic, n = 9 non-ruptured symptomatic, and n = 14 ruptured AAAs. We calculate maximum values for diameter, wall displacement, strain, stress, and RPI as well as minimum wall strength for every AAA. All investigated quantities, except minimum strength, show statistically significant differences between non-ruptured asymptomatic and symptomatic/ruptured AAAs. Maximum wall stress and especially the RPI are notably increased for symptomatic and ruptured AAAs. The biggest difference is found to be the RPI (Δ = 44.9%, p = 8.0e−5). Lowest RPI obtained for symptomatic or ruptured AAAs is 0.3. The RPI of more than 55% of the investigated asymptomatic AAAs falls below this value. Maximum wall stress and maximum RPI criteria enable a reliable rupture risk evaluation for AAAs. Especially in the diameter range where surgical indication is not obvious, the RPI holds great potential for improvement of clinical decisions.
Pulmonary vein isolation (PVI) is the cornerstone of atrial fibrillation (AF) ablation in persistent AF (persAF), and cryoballoon PVI emerged as an initial ablation strategy. Symptomatic atrial ...arrhythmia recurrence following successful PVI in persAF is observed more frequently than in paroxysmal AF. Predictors for arrhythmia recurrence following cryoballoon PVI for persAF are not well described, and the role of left atrial appendage (LAA) anatomy is uncertain.
Patients with symptomatic persAF and pre-procedural cardiac computed tomography angiography (CCTA) images undergoing initial second-generation cryoballoon (CBG2) were enrolled. Left atrial (LA), pulmonary vein (PV) and LAA anatomical data were assessed. Clinical outcome and predictors for atrial arrhythmia recurrence were evaluated by univariate and multivariate regression analysis.
From May 2012 to September 2016, 488 consecutive persAF patients underwent CBG2-PVI. CCTA with sufficient quality for measurements was available in 196 (60.4%) patients. Mean age was 65.7 ± 9.5 years. Freedom from arrhythmia was 58.2% after a median follow-up of 19 (13; 29) months. No major complications occurred. Independent predictors for arrhythmia recurrence were LAA volume (HR 1.082; 95% CI, 1.032 to 1.134;
= 0.001) and mitral regurgitation ≥ grade 2 (HR, 2.49; 95% CI 1.207 to 5.126;
= 0.013). LA volumes ≥110.35 ml sensitivity: 0.81, specificity: 0.40, area under the curve (AUC) = 0.62 and LAA volumes ≥9.75 ml (sensitivity: 0.56, specificity 0.70, AUC = 0.64) were associated with recurrence. LAA-morphology, classified as chicken-wing (21.9%), windsock (52.6%), cactus (10.2%) and cauliflower (15.3%), did not predict outcome (log-rank,
= 0.832).
LAA volume and mitral regurgitation were independent predictors for arrhythmia recurrence following cryoballoon ablation in persAF. LA volume was less predictive and correlated with LAA volume. LAA morphology did not predict the clinical outcome. To improve outcomes in persAF ablation, further studies should focus on treatment strategies for persAF patients with large LAA and mitral regurgitation.
Biogeophysical (BGP) and biogeochemical (BGC) effects of land-use and land cover change (LULCC) are separated at the global and regional scales in new interactive CO2 simulations for the 21st ...century. Results from four earth system models (ESMs) are analyzed for the future RCP8.5 scenario from simulations with and without land-use and land cover change (LULCC), contributing to the Land-Use and Climate, IDentification of robust impacts (LUCID) project. Over the period 2006–2100, LULCC causes the atmospheric CO2 concentration to increase by 12, 22, and 66 ppm in CanESM2, MIROC-ESM, and MPI-ESM-LR, respectively. Statistically significant changes in global near-surface temperature are found in three models with a BGC-induced global mean annual warming between 0.07 and 0.23 K. BGP-induced responses are simulated by three models in areas of intense LULCC of varying sign and magnitude (between −0.47 and 0.10 K). Modifications of the land carbon pool by LULCC are disentangled in accordance with processes that can lead to increases and decreases in this carbon pool. Global land carbon losses due to LULCC are simulated by all models: 218, 57, 35 and 34 Gt C by MPI-ESM-LR, MIROC-ESM, IPSL-CM5A-LR and CanESM2, respectively. On the contrary, the CO2-fertilization effect caused by elevated atmospheric CO2 concentrations due to LULCC leads to a land carbon gain of 39 Gt C in MPI-ESM-LR and is almost negligible in the other models. A substantial part of the spread in models' responses to LULCC is attributed to the differences in implementation of LULCC (e.g., whether pastures or crops are simulated explicitly) and the simulation of specific processes. Simple idealized experiments with clear protocols for implementing LULCC in ESMs are needed to increase the understanding of model responses and the statistical significance of results, especially when analyzing the regional-scale impacts of LULCC.
Zusammenfassung
Vermittlungsprozesse auf dem Arbeitsmarkt verlaufen zunehmend unter Mitwirkung von Plattformunternehmen: Online-Stellenbörsen, Karrierenetzwerken, Gigwork- und ...Crowdworking-Plattformen oder Arbeitgeberbewertungsportalen. Auf der Basis explorativer Internetrecherchen und Dokumentanalysen wird ein Überblick über die Plattformmodelle und ihre Verbindungen zu etablierten Akteuren der Beschäftigungsindustrie, vor allem Zeitarbeitsfirmen und Personalberatungen, gegeben. Mit Bezug auf Theoriekonzepte der Plattformforschung und der Arbeitsmarktanalyse (Infrastruktur, Intermediarität, Ökosystem, Feld) werden Thesen zur Rolle der Plattformen innerhalb der Beschäftigungsindustrie formuliert. In Anbetracht etablierter Strukturen und spezifischer Anforderungen des Arbeitsmarkts finden sich Plattformen in diesem Feld in komplexen Akteurskonstellationen wieder, die sie nicht in der Weise dominieren, wie das von Plattformkonzernen wie Amazon, Facebook oder Google angenommen wird. Privatwirtschaftliche Dienstleistungen der Arbeitskraftvermittlung gewinnen erheblich an Relevanz: Neben der Verfügung über die Daten stellen vor allem das Expertenwissen der Personalberatungen und der politische Einfluss der Zeitarbeitsfirmen maßgebliche Machtressourcen am Markt dar. Die Analyse lässt auf multiple Entwicklungspfade der Plattformökonomie schließen – und auf die Notwendigkeit stärker vergleichender Forschung.
Based on the Max Planck Institute Earth System Model simulations for the Coupled Model Intercomparison Project Phase 5 and on simulations with the submodel Cbalone we disentangle the influence of ...natural and anthropogenic vegetation changes on land carbon emissions for the years 1850 until 2300. According to our simulations, climate‐induced changes in distribution and productivity of natural vegetation strongly mitigates future carbon (C) emissions from anthropogenic land‐use and land cover change (LULCC). Depending on the assumed scenario, the accumulated carbon emissions until the year 2100 are reduced between 22 and 49% and until 2300 between 45 and 261%. The carbon storage due to climate‐induced vegetation change is generally stronger under the presence of LULCC. This is because the natural vegetation change can reestablish highly productive extratropical forests that are lost due to LULCC. After stopping anthropogenic vegetation changes in the year 2100 the refilling of depleted C pools on formerly transformed land takes (dependent on the scenario) time scales of centuries.
Key Points
Future natural vegetation change can mitigate CO2 emissions from LULCC
Possible interdependencies between future natural vegetation changes and LULCC
The refilling of carbon pools after stopping LULCC takes century time scales
Anthropogenic land cover change (ALCC) influences global mean temperatures via counteracting effects: CO2 emissions contribute to global warming, while biogeophysical effects, in particular the ...increase in surface albedo, often impose a cooling influence. Previous studies of idealized, large‐scale deforestation found that albedo cooling dominates over CO2 warming in boreal regions, indicating that boreal reforestation is not an effective mitigation tool. Here we show the importance of past land use decisions in influencing the mitigation potential of reforestation on these lands. In our simulations, CO2 warming dominates over albedo cooling because past land use decisions resulted in the use of the most productive land with larger carbon stocks and less snow than on average. As a result past land use decisions extended CO2 dominance to most agriculturally important regions in the world, suggesting that in most places reversion of past land cover change could contribute to climate change mitigation. While the relative magnitude of CO2 and albedo effects remains uncertain, the historical land use pattern is found to be biased towards stronger CO2 and weaker albedo effects as compared to idealized large‐scale deforestation.
Key Points
Past land use decisions increased the mitigation potential of reforestation
CO2 effects are stronger for historical as compared to idealized deforestation
Albedo effects are weaker for historical as compared to idealized deforestation
PDF
