# Forecast Analysis of Pollutant Emissions of Cruise Ship Routes in Western Mediterranean
## 1 Introduction  
The environmentally sustainable operation of ships is a key goal for the shipping industry. The International Maritime Organisation (IMO) is actively working towards the 2030 Agenda and is contributing to the implementation of the Sustainable Development Goals (SDGs) both through providing the legislative framework for international shipping that enables sustainable development and through specific capacity-building activities. SDG13 (climate change) is identified as one of the most impactful areas of its work [1]. Cruse lines, as part of the shipping industry, are concerned about the environmentally sustainable operation of ships and about achieving the goals of the 2030 Agenda, among which SDG13 stands out. The cruise industry has an ambitious environmental agenda seeking the long-term sustainability of the industry. Accordingly, the global cruise industry has many initiatives to reduce greenhouse gas (GHG) emissions. For instance, it has the commitment to reduce the rate of carbon emissions across the industry fleet by 40 per cent by 2030 [2]. In addition, achieving a net zero carbon cruising footprint by 2050 is among the environmental goals pursued by the industry. The cruise industry was hard hit by the COVID-19 pandemic, with an unprecedented stoppage of cruise fleets in March 2020. The cessation of operations of the cruise fleet hadmany negative consequences, among which are the bankruptcy of some cruise lines, such as Pullmantur Cruises or FTI Berlin, and the early scrapping of 16 vessels by the end of 2021 (most of them very elderly). An immediate consequence of the COVID-19 outbreak was a decline in worldwide cruise passenger volume from 29.7 million in 2019 to 5.8 million and 4.8 million in 2020 and 2021, respectively [3]. The Caribbean Sea is the worldwide leader in terms of deployed capacity and maintained its leadership even during the pandemic period. In 2019, the deployed capacity in the Caribbean Sea was at 38.7%, while in 2020 and 2021, it was at 49.6% and 35.8%, respectively. The Mediterranean continued as the second-largest cruise destination also during the pandemic period. It registered a deployed capacity of 14.8% in 2019 (the pre-pandemic year). The pandemic outbreak lowered the share of the Mediterranean to 9.3% of the worldwide capacity in 2020, while in 2021, the share was at 20% [4; 5]. The extremely low deployed capacity in 2020 is because the pandemic outbreak started at the gates of the peak season in the Mediterranean. Fortunately, as a sign of the resilience of the cruise industry, its recovery is close, as cruise traffic performance indicators in 2022 showed; see Tables 1 and 2. It is expected that by 2023, the industry will recover the volume registered in 2019. Moreover, forecasts indicated that in 2023 the cruise industry would surpass the passenger volume of 2019 [6]. In this recovery scenario, compliance with the environmental objectives set by the 2030 Agenda and the commitment made by the cruise industry in this regard cannot be forgotten. The environmental impact of cruise ship activity is associated with multiple sources: liquid and solid waste, garbage generated by its activity, and emissions of polluting gases. The International Convention for the Prevention of Pollution from Ships (MARPOL 73/78) is the core regulation worldwide to limit the pollution from ship activities [7]. Annex VI of MARPOL 73/78 is the main international regulation for the prevention of air pollution from ships through the limitation of SO\({}_{\rm x}\) and NOx emissions. Moreover, focusing on Europe, the Directive (EU) 2016/802 limits the sulfur content of certain liquid fuels [8]. The current limit of 0.5% of the content of sulfur for marine fuel entered into force on 1 January 2020 [9]. Regarding the Mediterranean, in December 2022, it was designated as an emission control area for sulfur oxides, which will enter into force on 1 May 2025 [10]. This means that the permissible sulfur content of the marine fuel to be used will fall from the current limit of 0.5% to 0.1%.