## 3 Material and Methods
### Sea-Level Data  
The analysis of sea-level data collected at the tidal networks located in the Mediterranean basin highlighted a mean rate of sea-level rise of about 1.8 mm/year for the last two-three centuries [70], although local VLMs can influence, even severely, the mean trend [102]. The closest tide gauge station in the investigated area of south eastern Sicily is located in the harbor of Catania (ISPRA tidal network, www.mareografico.it, accessed on 1 January 2021 [103]). The analysis of the time series of monthly mean sea-level data collected in the time span 1992-2020, shows a trend at 4.66 \(\pm\) 0.01 mm/year (Figure 5), which is about 2.9 mm/year higher than the average rate for the Mediterranean Sea. It is worth noting that InSAR analysis detected a local land subsidence at about 2 mm/year in the proximity of the coast of Catania (Figures 3 and 4) that affects sea-level recordings. In addition, RSR for this location could be exacerbated by additional subsidence due local instabilities of the tidal station location being placed at the top of a large pier in the Catania harbor (Station coordinates Lat 37\({}^{\circ}\)29\({}^{\prime}\)44.42\({}^{\prime\prime}\)N; Long 15\({}^{\circ}\)05\({}^{\prime}\)42.11\({}^{\prime\prime}\)E).  
Figure 5: Monthly sea-level at the tide gauge station of Catania in the time span 1986–2020. The linear trend (red line), calculated in the time interval 1992–2020, corresponds to a rate of 4.66 mm/year. Recordings between 1986 and 1992 have been excluded in the analysis due to a relocation of the station.  
In order to project the expected sea-levels at 2050 and 2100 A.D. for the coast of south eastern Sicily, the novel sea-level projections based on the IPCC special report \"The Ocean and Cryosphere in a Changing Climate (SROCC)\" [7], released in 2019, were adopted. SROCC estimates consist of sea-level median values and standard errors on a worldwide grid obtained by summing up the contributions of geophysical sources driving long-term sea-level changes. The considered sources of sea-level variations are: the thermosteric/dynamic contribution (from the same 21 CMIP5 coupled atmosphere-ocean general circulation models AOGCMs used for AR5 IPCC projections), the surface mass balance and dynamic ice sheet from Greenland and Antarctica, the glacier and land water storage, the glacial isostatic adjustment (GIA) and the inverse barometer effect. As for the AR5 IPCC, SROCC projections are provided for three different RCPs 2.6, 4.5 and 8.5: in the RCP 2.6 scenario the emissions of greenhouse-gas emission peak around 2020, in RCP 8.5 they continue to grow throughout the century [104]. SROCC and AR5 IPCC sea-level projections only differ in the estimates of the contributions from Antarctica: new ice-sheet modelling results, not available at the time of AR5, have been incorporated into the SROCC assessment. The difference between global mean sea-levels in SROCC and AR5 IPCCs is negligible under RCP 2.6 and RCP 4.5 scenarios while it is about 10 cm in 2100 under RCP 8.5.  
The predicted sea-level rise in the south-eastern margin of Sicily has been estimated by combining the rate of sea-level rise at the grid point closest to Lat 37\({}^{\circ}\)2\({}^{\prime}\)54.32\({}^{\prime\prime}\)N; Lon 15\({}^{\circ}\)17\({}^{\prime}\)50.51\({}^{\prime\prime}\)E Gr, as provided by the SROCC projections, with the rate of vertical land motion inferred from InSAR data. In details, the measured rate of vertical land motion, which includes both GIA and tectonic components of both natural and anthropogenic origin, replaces the GIA contribution used in the original SROCC projections. Errors coming from the InSAR data are included in the overall uncertainty estimation.