The impacts of sea-level rise on European coasts in a 2°C world. Results and analysis of task 6.5 prepared as part of IMPACT2C: quantifying project impacts under 2°C warming

摘要

The European Union is at risk of the adverse effects of rising sea-levels, potentially leading to an increase in number of people affected by flood events and increased damage costs unless adaptation is undertaken. This research answers a question, ‘What are the impacts and costs of sea-level rise around Europe in a 2°C world?’ A 2°C world could occur rapidly under high emissions, or over much longer periods of time under climate mitigation. Climate mitigation is widely seen a way to reduce adverse risk, but in the coastal zone this is less effective and could only offer potential over very long time periods due to a time lag between atmospheric warming and oceanic response, known as the commitment to sea-level rise. As such, global mean sea-level in a 2°C world is projected to be between 0.11m (under high emissions) and 0.52m (under climate mitigation) higher than 1985-2005 levels under the HadGEM2-ES model. This makes quantifying impacts challenging.Using the Dynamic Interactive Vulnerability Assessment (DIVA) modelling framework, the number of people at risk from rising sea levels and flood costs have been analysed for scenarios of 2°C and extending up to a 5°C rise compared with pre-industrial levels in European Union coastal regions. Results indicate that following widespread European practices of continued protection, that between 5,300 and 7,000 people per year may be flooded in a 2°C world of climate mitigation – which could double if climate goes unmitigated. In a 5°C world, annual sea flood costs could be up to €1.2 billion per year, but reduce by one third under climate mitigation. The greatest costs occur around many countries surrounding the North Sea, where relatively, the EU’s smaller economies and small island states benefit most from climate mitigation.Adaptation remains particularly important, with sea dikes costing up to €3.9 billion per year in a 5°C world, decreasing by more than one sixth under climate mitigation. To achieve optimum benefits of adaptation and mitigation, it is essential that shoreline management and climate change adaptation are considered over the long time periods in which sea-level rise operates, taking into account multiple factors of coastal change. This includes a range of engineering techniques, including soft adaptation, accommodation and managed retreat, simultaneously considering wider societal needs and social acceptability of coastal change.