A methodology to transfer the uncertainty on future sea level scenarios into the risk assessment of related impacts

Current climate change is evident in many environmental aspects, among them there is the progressive increase of the average sea level.

The height of the sea water along the coasts is characterized by variations which are consequence of causes having different time scales, including periodic tidal oscillations, episodic atmospheric forcing events and long term trends, mainly due to climate change. The latter contributes in the means sea level, but affects the rare extreme phenomena too, both on their frequency and intensity.

Thus, a quantitative assessment of risks deriving from the sea level variations needs a robust quantification of all the elements bringing the sea level to become a hazard. In addition, it is required to define best practices on how to use mean sea level rise trends together with shorter time scales effects, in engaging risk assessment processes, according to the specific impacts.

Usually, scientific knowledge enters in the everyday use when its degree of uncertainty has already been reduced below a threshold, that keeps the contribution of that uncertainties marginal with respect to those of all the other sources of information, which enter in the realization of the practical result.

This is not the case of the adaptation and resilience solutions facing the impacts of sea level rise, due to climate change. In fact, future sea level scenario cannot be considered a robust parameter of the risk assessment process. On the other hand, stakeholders need to decide which kind of actions to adopt to minimize the impacts of a sea level.

To go beyond that weakness, we developed and tested a methodology to bring the scientific information, together with its uncertainty, into the risk assessment procedures.

Scientific information is not considered as a robust parameter anymore, but it is brought into the risk assessment as an ensemble of information, directly from numerical climate simulations. The sensitivity of the simulated impacts, from the hazard input data, transfers the scientific information into risk uncertainty.

Here we present the assessment cascade, that propagates the uncertainty on climate sea level rise and that on short term sea level variations along the risk assessment procedures down to the impact projection. Furthermore, the presentation of best practices is supported by examples of applications, that are aimed to help the stakeholder to flow the scientific information throughout the risk assessment logic.

The applications are summarized as ensembles of simulated impact and related risk curves as a function of the widely and commonly defined Global Warming Levels (GWLs: 1.5 °C, 2.0 °C, 3.0 °C, 4.0 °C).

This work has been conducted with the contribution from the EU co-financing in the frame of the Interreg Euro-MED Programme, thanks to the MedSeaRise Project.