A High-End Estimate of Sea Level Rise for Practitioners

Sea level rise (SLR) is a long-lasting consequence of climate change because global anthropogenic warming takes centuries to millennia to equilibrate for the deep ocean and ice sheets. SLR projections based on climate models support policy analysis, risk assessment and adaptation planning today, despite their large uncertainties. The central range of the SLR distribution is estimated by process-based models. However, risk-averse practitioners often require information about plausible future conditions that lie in the tails of the SLR distribution, which are poorly defined by existing models. Here, a community effort combining scientists and practitioners builds on a framework of discussing physical evidence to quantify high-end global SLR for practitioners. The approach is complementary to the IPCC AR6 report and provides further physically plausible high-end scenarios. High-end estimates for the different SLR components are developed for two climate scenarios at two timescales. For global warming of +2°C in 2100 (RCP2.6/SSP1-2.6) relative to pre-industrial values our high-end global SLR estimates are up to 0.9 m in 2100 and 2.5 m in 2300. Similarly, for a (RCP8.5/SSP5-8.5), we estimate up to 1.6 m in 2100 and up to 10.4 m in 2300. The large and growing differences between the scenarios beyond 2100 emphasize the long-term benefits of mitigation. However, even a modest 2°C warming may cause multi-meter SLR on centennial time scales with profound consequences for coastal areas. Earlier high-end assessments focused on instability mechanisms in Antarctica, while here we emphasize the importance of the timing of ice shelf collapse around Antarctica. This is highly uncertain due to low understanding of the driving processes. Hence both process understanding and emission scenario control high-end SLR.

A history of futures: A review of scenario use in water policy studies in the Netherlands

The future of human life in the world's river deltas depends on the success of water management. To deal with uncertainties about the future, policymakers in the Netherlands have used scenarios to develop water management strategies for the coastal zone of the Rhine-Meuse delta. In this paper we reflect on six decades of scenario use in the Netherlands, and provide recommendations for future studies. Based on two criteria, 'Decision robustness' and 'Learning success', we conclude that (1) the possibilities for robust decisionmaking increased through a paradigm shift from predicting to exploring futures, but the scenario method is not yet fully exploited for decisionmaking under uncertainty; and (2) the scenarios enabled learning about possible impacts of developments and effectiveness of policy options. New scenario approaches are emerging to deal with the deep uncertainties water managers are currently facing.

[Decision-making regarding life-sustaining medical treatment in a pediatric intensive-care unit]

The complexity of the decision-making process regarding life-sustaining medical treatment was illustrated by the single case of a 12-year-old boy with severe meningococcal septicaemia. When his clinical condition deteriorated, necessitating haemodialysis and multiple amputations of the extremities, questions about the futility of treatment and the future quality of life puzzled the attending physician. In consultation with the treatment team and the parents, it was decided to continue medical treatment in this patient since there was too little prognostic certainty concerning bodily functions and morbidity and the expected future quality of life. After 60 days, the patient was discharged. Half-a-year later he was following an intensive rehabilitation programme and the possibility of renal transplantation was contemplated. Because of the consequences for the child and his family, a decision to continue life-sustaining medical treatment should be justified as thoroughly as one to withdraw or withhold treatment.