Cleaner fuel for ships accelerated global warming: Study May 31, 2024

Cleaner fuel ships

By AFP - Agence France Presse

Cleaner fuel for ships accelerated global warming: Study

An international effort to improve air quality by requiring ships to use less polluting fuel has caused an increase in global warming, according to research published Thursday on this unintended climate “shock”.

The shift in global shipping to low-sulfur fuels from 2020 “could lead to a doubling (or more) of the warming rate” this decade and has already contributed to last year's record heat, according to the study.

This is because the tiny particles of sulfur pollution reflect and absorb sunlight, making clouds more mirror-like and creating a temporary cooling effect on the planet.

Scientists predicted that switching to cleaner fuels would reduce this reflection effect and accelerate warming, although they disputed to what extent.

The study suggests that deliberate cloud cleaning could reduce global warming, even if these measures do not address the underlying factor: the pumping of greenhouse gases into the atmosphere.

Scientists warn that these “geoengineering” approaches to climate change can have unwanted side effects and say that caution is needed.

For the new study, the researchers combined satellite observations and model simulations to estimate the climate impact of reducing sulfur in ship fuel by an International Maritime Organization regulation that came into force in January 2020.

Introduced to limit air pollution, this decision reduced sulfur dioxide emissions from the global shipping sector by 80%, said Tianle Yuan, lead author of the study published in Communications Earth and Environment.

But the rapid drop also had a “shock” effect on the planet, he added, decreasing the ability of clouds to reflect some of the sun's energy into space, resulting in a “substantial warming effect”.

“Essentially, this would double the warming rate of the 2020s,” the senior research scientist at NASA's Goddard Space Flight Center told AFP.

Yuan said that this effect was uneven across the world, but there seems to have been a stronger impact in the North Atlantic, leading to a warming of the sea surface temperature.

“This contributed to the anomalous warming we experienced in 2023 and 2024. However, we cannot precisely attribute how much” and it was not possible to say that it was the main cause, he added.

Last year was the hottest year on record and this trend will continue until 2024, with temperatures on land and in the sea reaching new monthly highs.

Human activities are the dominant cause of the warming, but the scientists also analyzed other possible contributions to this extraordinary heat, including the role of El Nino, a periodic natural weather pattern over the Pacific.

Nicolas Bellouin, a climatologist at Reading University, told AFP that this latest study is “scientifically more solid” than previous research and “should be taken seriously”.

“But I think the contribution of this warming to the 2023 anomaly and future warming rates remains an open question, even after this study,” said Bellouin, who was not involved in the research.

Other scientists said the study offered evidence that seeding clouds with particles to increase their ability to reflect heat could help partially slow warming if greenhouse gases continue to increase.

For some, geoengineering - which includes technologies to decrease the intensity of incoming sunlight or reduce acid levels in the oceans - is a distraction from tried and tested climate solutions.

Currently, there is no formal global governance for the development or deployment of such technologies, and an incomplete understanding of the risks they entail.

Edward Gryspeerdt, an expert in cloud physics at Imperial College London, said that there are still major uncertainties about the side effects of geoengineering, such as changes in rainfall patterns.

“These risks must be better understood to make informed decisions about any future geoengineering strategies,” he said.

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