Estimating air emissions from ships: Meta-analysis of modelling approaches and available data sources

Maritime transport plays a central role in the transport sector’s sustainability debate. Its contribution to air pollution and greenhouse gases is significant.An effective policy strategy to regulate air emissions requires their robust estimation in terms of quantification and location.This paper provides a critical analysis of the ship emission modelling approaches and data sources available, identifying their limits and constraints. It classifies the main methodologies on the basis of the approach followed (bottom-up or top-down) for the evaluation and geographic characterisation of emissions.The analysis highlights the uncertainty of results from the different methods. This is mainly due to the level of uncertainty connected with the sources of information that are used as inputs to the different studies. This paper describes the sources of the information required for these analyses, paying particular attention to AIS data and to the possible problems associated with their use. One way of reducing the overall uncertainty in the results could be the simultaneous use of different sources of information. This paper presents an alternative methodology based on this approach.As a final remark, it can be expected that new approaches to the problem together with more reliable data sources over the coming years could give more impetus to the debate on the global impact of maritime traffic on the environment that, currently, has only reached agreement via the “consensus” estimates provided by IMO (2009).

► Estimation of emissions from ships still needs further research.
► Uncertainties and errors in the data are key issues for this topic.
► AIS data are the most promising source of information for emissions calculation.
► Different types of errors in AIS data frequently occur and may undermine their reliability.
► Different data should be jointly used to reduce the uncertainty in estimations of global emissions.