Cleaner marine fuel is contributing to warming oceans, say scientists at ET EnergyWorld

SINGAPORE: Marine fuel regulations introduced in 2020 led to a significant reduction in sulfur dioxide (SO2) pollution, but may also have warmed the ocean by reducing cloud cover, according to a modeling study in a paper published late on Thursday.

International Maritime Organization (IMO) regulations to combat marine pollution forced shippers to reduce fuel sulfur content to 0.5% from 3.5%, leading to an 80% drop in SO2 emissions, according to a research team led by Tianle Yuan of University of Maryland.

However, SO2 is not only a major pollutant, but also masks global warming by creating aerosols that thicken and brighten clouds by reflecting sunlight back into space.

IMO fuel standards may have accounted for 80 percent of the planet’s total net heat gain since 2020, and the impact is particularly pronounced on busy shipping lanes, scientists estimated in a paper published in the journal Communications Earth & Environment.

Climate scientists have identified SO2 reductions as a potential contributing factor to record ocean temperatures last year. Some also suggest that reducing air pollution around the world may have accelerated global warming.

“This cooling effect (SO2) is well understood – and documented episodes have occurred as a consequence of several major SO2-emitting volcanic eruptions over the last 2,000 years,” said Stuart Haszeldine, director of the Edinburgh Climate Change Institute at the University of Edinburgh.

Haszeldine, who was not involved in the paper, said that while it was difficult to make accurate predictions about the impact on global temperatures, the trend was “very clear, extremely concerning and very significant.”

Other scientists said the study may have exaggerated the impact of IMO fuel policy.

“Research is ongoing into the cause of such high temperatures recently, and the reduced sulfur content in marine fuel is just one factor,” said Joel Hirschi from Britain’s National Oceanographic Center.

The authors said their research showed that “marine cloud brightening” could be a potential geoengineering solution to global warming.

Scientists have been looking for ways to reflect heat back into space, but proposals to inject SO2 into the atmosphere have sparked controversy. Other experiments have also been carried out by spraying seawater into the air to thicken clouds.

(Reporting by David Stanway; Editing by Tom Hogue)