Since the data in Euro stat are given in gross tonnes(GT) , they were converted in to dead weight tonnage(DWT) based on the average ratio for the worldwide fleet in 2008(Lloyd's Register/Fair play,2009).
Based on the ship types calling at ports and on their average size, it is possible to choose the appropriate ship emission factor to assess the total CO2 emissions. Emission factors are expressed in gCO2/t nm,(where lower figures represent greater efficiency).Values are derived from the aforementioned 2009 IMO GHG Study and are listed in Table 5. The see mission actors are applied to all vessel voyages with an origin or arrival from or to a particular port.