Study Confirms Sharp Drop in Shipping Sulfur Emissions After IMO 2020

A new investigation by the UK’s National Centre for Atmospheric Science (NCAS) confirms that the global shipping sector has dramatically reduced its sulfur output following the International Maritime Organization’s 2020 sulfur cap. Published in *Environmental Science: Atmospheres*, the research analysed emissions between 2019 and 2023 in the North‑East Atlantic and adjacent European coastal waters.

Methodology

The study combined direct measurements with advanced modelling to quantify changes in fuel sulphur content and resulting emissions. Key components included:

• **Aircraft‑borne sensors** – flying over shipping lanes to sample exhaust plumes.
• **Ground‑based instruments** – positioned along coastlines to capture local emissions.
• **Emission models** – calibrated with the collected data to estimate fuel sulphur levels before and after the IMO regulation.

By integrating these data streams, the team was able to derive a robust picture of how the 0.5% sulphur limit has been adopted in practice.

Findings

• **Ten‑fold reduction in sulphur content** – Ships operating on the open ocean now use bunker fuel that contains roughly one‑tenth the sulphur of pre‑IMO 2020 fuel.
• **Seven‑fold drop in sulfur emissions** – The overall shipping sector’s sulfur output has fallen by about 85 % since the rule took effect.
• **Continued importance of shipping** – Despite the reduction, maritime transport remains the largest human source of marine sulphur, accounting for around 13 % of global emissions.

Professor Hugh Coe, an atmospheric composition scientist at NCAS and the University of Manchester, highlighted the significance of these results: "Shipping is the most important human source of sulfur in marine environments, largely found as sulfur dioxide, and is estimated to be responsible for around 13% of global sulfur emissions." This statement underscores the sector’s ongoing influence on marine air quality.

Market Implications

While the study focuses on environmental outcomes, the findings carry clear market signals for the marine fuels industry:

1. **Demand for low‑sulphur fuels** – The sharp decline in sulfur usage confirms that the market has largely shifted to VLSFO and other compliant grades. 2. **Price dynamics** – As vessels adopt cleaner fuels, price spreads between high‑sulphur and low‑sulphur products are likely to tighten, reflecting the reduced need for high‑sulphur options. 3. **Regulatory compliance** – Shipping operators continue to face stringent sulphur limits, reinforcing the importance of accurate fuel specification and bunkering practices.

The study’s evidence of a tangible reduction in emissions aligns with earlier estimates and provides a solid baseline for future regulatory and market developments. It also reinforces the role of rigorous monitoring and transparent reporting in tracking progress toward cleaner marine operations.

Looking Ahead

The NCAS research demonstrates that the IMO 2020 rule has delivered measurable environmental benefits. Continued vigilance through independent measurement and modelling will be essential to ensure that the sector maintains its trajectory toward lower sulphur emissions and supports broader climate objectives.

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*Sources: NCAS, *Environmental Science: Atmospheres* (2025).