# Forecast Analysis of Pollutant Emissions of Cruise Ship Routes in Western Mediterranean
## 4 Results
### Forecast Analysis of Gas Emissions
In the case of the projections for SO\({}_{2}\), two approaches were applied, one without the implementation of the SECA and another with the implementation of the SECA. The projection of the optimistic scenario leads to an increase of 16.1% of NO\({}_{\rm x}\) in 2025 with respect to 2019 emissions, whereas for SO\({}_{2}\), the emissions will be reduced up to 76.8% with the SECA implemented, and CO\({}_{2}\) emissions will increase by up to 16.0%. On the contrary, the pessimistic scenario in terms of the evolution of the cruise traffic in the Western Mediterranean for 2025 would decrease NO\({}_{\rm x}\) emissions by up to 5.0%, SO\({}_{2}\) emissions would decrease by up to 81.0% if the SECA is implemented, and CO\({}_{2}\) would decrease by up to 5.0%. Moreover, the emissions for the optimistic scenario in the 2025 year would be 18% higher than the emissions for the same year considering the pessimistic scenario. Focusing on the effects of the enforcement of the SECA in the Mediterranean, the emissions of SO\({}_{2}\) will drop up to 80%, from 5225 t to 1045 t, in the optimistic scenario; see Figure 5b. Furthermore, different SFCs are considered to explore how different SFC ratios can affect overall gas pollutant emissions. We considered an SFC ranging from \(\pm\)10% of the reference SFC given by engine manufacturers. Figure 6 shows the results for NO\({}_{\rm x}\) gas emissions. The maximum reduction in emissions with \(-\)10% of reference SFC would be 84.2% for the fifth scenario, as in Figure 6b, and 78.6% for +10% of reference SFC for the fifth scenario, as in Figure 6a, if variation in the SFC is considered. Figure 5: _Cont._  
Figure 5: Results of the projections of pollutant gas emissions considering five scenarios of evolution of cruise traffic: (**a**) NO\({}_{\kappa}\); (**b**) SO\({}_{2}\); and (**c**) CO\({}_{2}\). Note: the red dashed line on the projection of SO\({}_{2}\) emissions indicates the difference between the results for 2025 without the enforcement of the SECA and with the enforcement of the SECA, respectively. Figure 7 shows the results for SO\({}_{2}\) gas emissions considering \(\pm\)10% of the SFC with respect to the reference SFC and with two approaches for the year 2025, with (and without) the implementation of the SECA in the Mediterranean taking effect. In the optimistic scenario with the SECA implemented and an SFC 10% lower than the reference SFC, SO\({}_{2}\) emissions could be 26% lower than the emissions associated with the same scenario and an SFC 10% higher than the reference SFC. The implementation of the SECA in the Mediterranean will have a positive footprint in improving the sustainability of cruise activities. Figure 6: NO\({}_{\rm x}\) gas emissions for the five scenarios of evolution of cruise traffic considering an SFC \(\pm\)10% with respect to the reference SFC: (**a**) SFC 10% higher than the reference SFC and (**b**) SFC 10% less than the reference SFC. Figure 8 corresponds to the results obtained for CO\({}_{2}\) gas emissions considering \(\pm\)10% of the SFC with respect to the reference SFC. Differences in the optimistic scenario for higher and lower SFCs for 2025 would reach up to 18.2% of emissions. In the same way, differences between the optimistic and pessimistic scenarios for 2025 would reach 18.1%. Figure 7: SO\({}_{2}\) gas emissions for the five scenarios of evolution of cruise traffic considering an SFC \(\pm\)10% with respect to the reference SFC: (**a**) SFC 10% higher than the reference SFC and (**b**) SFC 10% less than the reference SFC. Note: the red dashed line on the projections indicates the difference between the results for 2025 without the enforcement of the SECA and with the enforcement of the SECA, respectively.