Carbon footprints: Uncovering multilevel spatiotemporal changes of ship emissions during 2019–2021 in the U.S

• Published in: The Science of the total environment 2024-02, Vol.912, p.169395-169395, Article 169395
• Main Authors: Mou, Naixia, Zhang, Xianghao, Yang, Tengfei, Xu, Huanqing, Zheng, Yunhao, Wang, Jinhua, Niu, Jiqiang
• Format: Article
• Language: English
• Subjects: Activity-weighted method; AIS data; Multilevel geographic analysis; Ship carbon emissions; U.S. Exclusive Economic Zone
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2023.169395

Quantifying and understanding changes in carbon emissions is essential for the U.S. shipping industry to reduce carbon emissions, especially after its return to the Paris Agreement. We estimated carbon emissions from 48,321 ships in the U.S. Exclusive Economic Zone (EEZ) using the power-based method based on 3.6 billion Automatic Identification System (AIS) reports. We explored the characterization of carbon emissions from the national, regional, and port levels during 2019–2021 by allocating emissions on a 1 km*1 km grid through an activity-weighted method. The results show: (1) Due to the COVID-19 pandemic, emissions within the EEZ show a temporal trend of decreased and then rebound, specifically from 32.628 Tg in 2019 to 30.741 Tg in 2020 and then bounced to 31.786 Tg in 2021. The spatial differences in emissions show significant heterogeneity; (2) There are significant differences in emissions by vessel type, flag, and operational mode for the four regions of the U.S. (Great Lakes, Gulf Coast, Pacific Coast, and Atlantic Coast). Thus, emissions in these regions show different variability patterns over three years. Notably, “port congestion” led to record high emissions on the Pacific Coast; (3) Containerized cargo contributes the most to port core area emissions, so most ports with higher throughputs have higher emissions, with Long Beach and Los Angeles having the highest. Emissions from coastal ports are high and volatile, while inland ports are low and stable. This study provides the U.S. with a high spatiotemporal resolution inventory of carbon emissions from ships, and the findings are expected to provide some reference for controlling ship emissions. [Display omitted] •First comprehensive carbon emissions assessment of ships in the U.S. exclusive economic zone•Over 3.6 billion AIS records for 48,321 ships from 2019 to 2021 were used to estimate emissions.•A power-based method was used to calculate carbon emissions.•An activity-weighted method was used to allocate carbon emissions.•Changes in emissions from the national, regional, and port levels were analyzed.