Data sources

Climate data

The historical climate data used to produce the risk measures are hourly ERA5 reanalysis data from Copernicus, the European Union's Earth observation programme. The data cover the Earth and resolve the atmosphere using 137 levels from the surface to a height of 80 km. The application of downscaling methods preserving trends and distributions allows a granularity of 0.1°C, or about 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 of the Intergovernmental Panel on Climate Change (IPCC) Sixth Assessment Report. Using a multi-model approach reduces biases and uncertainties associated with each global climate model.

Field data

The terrain data comes from FABDEM+ derived from FABDEM, and the Copernicus GLO-30 digital elevation model. FABDEM is supplemented by high-resolution digital terrain model sets, such as LiDAR. Copernicus's GLC, ETH GCH, WSF3D, allowing for detailed consideration of forest cover, slope, and urbanization. The resolution is 1 arc second, or about 20m in France.

Hydraulic data

The hydraulic model is based on the local inertial formulation of shallow water equations, deployed globally. River sizes are simulated using a progressively varying flow solver at a granularity of about 20m in Europe. The pluvial boundary conditions are defined by the Intensity-Duration-Frequency relationships. The coastal boundary conditions are generated using a regional frequency analysis. The hydraulic model is calibrated by machine learning from observational data, watershed descriptors, and river gauges, to produce grids of fluvial, pluvial, and coastal flood depths.

Scenarios

RCP (Representative Concentration Pathways) scenarios are greenhouse gas concentration trajectories. Four scenarios were 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 the radiative forcing, i.e. the difference between incoming and outgoing radiation expressed in W/m2. The RCP 2.6 scenario is the most optimistic scenario, with a peak in emissions reached before 2050, which does not exceed a temperature increase of 1.5°C above the temperature of the pre-industrial era. The 8.5 scenario is the scenario for which emissions continue to increase at the current rate, leading to a temperature increase greater than 4°C by 2100.