(LEEDS, England) — Recent global regulations have significantly reduced sulfur emissions from ships, helping to improve air quality in coastal regions – confirmed by a new international study led by researchers at the National Centre for Atmospheric Science (NCAS).
The research, published in Environmental Science: Atmospheres, used aircraft and ground-based instruments to measure sulfur dioxide and nitrogen oxides emitted by ships in northeast Atlantic and European coastal waters between 2019 and 2023.
The team found that the average sulfur content in ship fuel dropped nearly tenfold in open ocean areas following the International Maritime Organization’s (IMO) 2020 regulation, which capped sulfur content in marine fuel at 0.5 percent.
Before the change, many ships exceeded the previous 3.5 percent limit. After 2020, only a small number of ships were found to breach the new standard.
In European Sulfur Emission Control Areas (SECAs), such as the English Channel and the Port of Tyne, sulfur levels were even lower – well below the stricter 0.1 percent limit. Interestingly, ports outside these zones, like Valencia in Spain, also showed low sulfur levels, likely due to European Union (EU) rules requiring cleaner fuel when ships are docked for extended periods.
This is the first study to use aircraft-based measurements and predictions from the Ship Traffic Emission Assessment Model (STEAM3) to assess ship emissions outside of sulfur control zones since the 2020 regulation came into effect. The findings support the widely held view that ships now emit around seven times less sulfur than before the rule change – an important step toward cleaner air and healthier coastal environments.
“Large amounts of sulfur in the atmosphere can be detrimental for people’s health and the environment,” said Professor Hugh Coe, atmospheric composition research scientist at NCAS and the University of Manchester. “It’s important to understand where sulfur emissions come from and how they behave, because it helps us make better predictions about air quality and our changing climate. 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 percent of global sulfur emissions.”
“There was a large reduction in the maximum allowed sulfur emission from ships in 2020, so we wanted to measure emissions before (in 2019) and after the change (in 2021 and 2022) to see what the effect was,” said Professor James Lee, an atmospheric chemist at NCAS and the University of York.
Regulations are different in ports and inland waterways compared to the open ocean, so using an aircraft was the only way to get the open ocean measurements, Lee said.
“Because of their location, often a long distance from land, emissions from ships are difficult to study,” he said. “Compared to ports, inland waterways, or special sulfur control zones, ships actually spend most of their time in the open ocean. This is also where they produce most of their emissions.”
The study was limited to the eastern North Atlantic Ocean, English Channel and two European ports, so measurements in other parts of the world would be required to see if this result is representative of the global shipping industry, Coe said.
– National Centre for Atmospheric Science
