Atmospheric impacts and regulation framework of shipping emissions: achievements, challenges and frontiers

Currently, over 80% of the international trade volume is carried by sea. Marked by persistent growth, evident atmospheric impacts, intricate mitigation challenges, international shipping has been recognized as one of the most “hard-to-abate” sectors gathering increasing attention from both academic community and governmental sectors in recent years. Against the backdrop of the ambitious climate and clean air objectives, the quantitative shipping emission characterization, impact assessment and policy effectiveness research are not only fundamental to understand the status quo and ramifications of shipping emissions but also beneficial for future emission regulations. Here, we summarized the achievements in shipping emission modelling and impact research in the past two decades, and identified the challenges lying in the transition pathway towards a clean and carbon-neutral shipping. To address the pressing demand for this, we proposed an innovative framework which aims to facilitate emission abatement. Finally, promising directions for future work were delineated, including the indirect effects of shipping emitted aerosols on the climate, the emissions and impacts of novel contaminants, synergies and conflicts among different emission reduction measures, projections on future shipping emission inventories, Arctic shipping emissions, etc.