Data sources

Climate data

The historical climate data used to produce the risk measurements are ERA5 hourly reanalysis data from Copernicus, the European Union's Earth observation program. The data covers the Earth and resolves the atmosphere using 137 levels from the surface down to a height of 80 km. The application of downscaling methods to preserve trends and distributions enables a granularity of 0.1°C, or around 10km in Europe.

Projection data

Projected climate metrics to 2100 are calculated from daily and monthly data as part of the sixth phase of the Coupled Model Intercomparison Project (CMIP6), the basis for the 6th Assessment Report of the Intergovernmental Panel on Climate Change (IPCC). The use of a multi-model approach reduces the biases and uncertainties associated with each global climate model.

Field data

Terrain data are derived from FABDEM+, a derivative of FABDEM, and the Copernicus GLO-30 digital elevation model. FABDEM is complemented by high-resolution digital terrain model ensembles, such as LiDAR. Copernicus's GLC, ETH GCH, WSF3D, allowing for fine-scale consideration of forest cover, slope and urbanization. Resolution is 1 arcsecond, or around 20m in France.

Hydraulic data

The hydraulic model is based on the local inertial formulation of the shallow water equations, deployed worldwide. River size is simulated using a smoothly varying flow solver at a granularity of around 20m in Europe. Rainfall boundary conditions are defined by Intensity-Duration-Frequency relationships. Coastal boundary conditions are generated using a regional frequency analysis. The hydraulic model is calibrated by machine learning from observation data, catchment descriptors and river gauges, to produce river, rainfall and coastal flood depth grids.

Scenarios

RCP (Representative Concentration Pathways) scenarios are greenhouse gas concentration trajectories. Four scenarios have been selected by the IPCC, based on RCP 2.6, RCP 4.5, RCP 6.0 and RCP 8.5. The number associated with RCP represents radiative forcing, i.e. the difference between incoming and outgoing radiation expressed in W/m2. RCP 2.6 is the most optimistic scenario, with emissions peaking before 2050, enabling a temperature rise of 1.5°C above pre-industrial levels not to be exceeded. Scenario 8.5 is the scenario in which emissions continue to rise at the current rate, leading to a temperature rise of over 4°C by 2100.

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