High-resolution global shipping emission inventory by Shipping Emission Inventory Model (SEIM): Insights into multiyear spatiotemporal variability, pandemic impacts, and emerging Arctic shipping emissions

The high-resolution ship emission inventory plays a critical role across multiple disciplines, including atmospheric and marine sciences as well as environmental management. In this study, we present a global high spatiotemporal resolution ship emission inventory developed using the Shipping Emission Inventory Model (SEIMv2.2) at a resolution of 0.1° × 0.1° for the years 2013, 2016–2021. Leveraging 30 billion Automatic Identification System (AIS) signals, SEIMv2.2 integrates real-time vessel positions, speeds, and technical parameters to model ship emissions from the bottom-up for key species, including CO2, NOx, SO2, PM2.5, CO, HC, N2O, CH4, and BC. According to our inventory results, which are freely accessible online (https://zenodo.org/records/11069531), temporally, global ship emissions exhibited minimal daily fluctuations. Spatially, high-resolution datasets revealed varying patterns of ship emission contributions by different vessel types across maritime regions. Research on the high spatiotemporal resolution ship emission inventory model SEIMv2.2 has been accepted by Earth System Science Data (https://essd.copernicus.org/preprints/essd-2024-258/).

 

Using our inventory, it is possible to reveal the variability of ship emissions across different regions and temporal scales. Taking 2020 as an example, we found that overall ship emissions of NOx, CO, HC, CO2, and N2O declined by 7.4%–13.8%, primarily due to the impacts of the COVID-19 pandemic. In the meanwhile, ship emissions of SO2, PM2.5, and BC dropped significantly by 40.9%–81.9% in 2020 compared to 2019, mainly driven by the implementation of low-sulfur fuel regulations. Focusing on the pandemic's influence, temporally, the largest drop in global ship emissions occurred in February 2020, followed by a gradual recovery in September as trade demand rebounded. Spatially, the shock originated in Asia and gradually extended to Europe and North America. Our analysis of the spatiotemporal variability of global ship emissions during the pandemic highlights the resilience of global maritime emissions, evidenced by the relatively small impact of the pandemic and the rapid pace of recovery. This resilience can be attributed partly to robust trade demand, and partly to the connectivity of maritime trade across continents, stemming from the fact that the trade in one region begins to recover, it often stimulates recovery in its trading partners. Research on the spatiotemporal variability of global ship emissions during the pandemic has been published online (https://www.sciencedirect.com/science/article/pii/S0048969724067895).

 

We further examined the characteristics of ship emissions in the Arctic region (defined as the area north of 60°N), which has been attracting research interests in recent years. Between 2016 and 2021, Arctic ship BC emissions increased by 6%, accounting for 1.5% of global ship emissions in 2021. Seasonally, BC emissions from ships during the Arctic summer (July–September) were 1.3 times higher than those in winter (January–March). In terms of vessel type contributions, cargo ships (including general cargo ships, bulk carriers, and container ships) accounted for 44.8% of BC emissions, followed by fishing vessels at 34.8% and oil tankers at 15.0%, in 2021. In the future, distinguishing between ship emissions driven by different transportation demands, such as transit cargo transport and energy transport is crucial for scientifically predicting future Arctic ship emissions and developing effective Arctic ship emission reduction strategies.