August 14, 2024
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Cleaning ship exhaust gases will make global warming even more severe
New shipping regulations limited the sulfur content of marine fuel, reducing harmful pollution but unintentionally halting its cooling effect on the Earth’s climate.
A cargo ship at the entrance to the Panama Canal on September 24, 2023.
Luis Acosta/AFP via Getty Images
Privacy Policy Efforts to reduce air pollution on the high seas may have had the unintended side effect of accelerating global warming.
This is according to a study published in the journal Science on Monday. Geophysical Research Letters.
The authors looked at environmental regulations introduced by the International Maritime Organization in 2020 that aim to reduce the amount of sulphur emitted by ships around the world.
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The researchers found that the restrictions may have unintentionally increased global temperatures by 0.04 degrees Celsius (about 0.07 degrees Fahrenheit) since 2020 because sulfur helps clouds cool the planet.
The temperature rise the scientists estimated represents about 17% of the warming caused by greenhouse gas emissions over the past few years, the paper noted, meaning the new regulations will be a major contributor to the recent rise in temperatures, including the phenomenal global heatwave of 2023 that will go down in history as the hottest year on record.
And researchers warn that global warming is likely to continue.
The researchers suggest that the new shipping rules could lead to an additional 0.03 degrees Celsius or more of warming. As a result, the new regulations “could be seen as an unintended experiment in solar geoengineering – but quite the opposite,” the new study says.
At first glance, this concept may sound counterintuitive: Pollution controls are meant to protect the planet and safeguard human health, so how could they potentially cause global temperatures to soar?
Scientists say the answer is rooted in physics: Certain air pollution particles cause clouds to form faster and shine brighter, reflecting sunlight away from the Earth and cooling the atmosphere in the process.
Sulfur particles are the fuel of choice for clouds, and are also the main component of shipping pollution, which is why ships often leave bright wakes behind them as they travel across the ocean.
The 2020 IMO regulations imposed new limits on the sulfur content of ship fuel to reduce harmful air pollution, but in doing so they also removed a powerful cloud-forming agent from the atmosphere, meaning there are fewer clouds to reflect sunlight away from the Earth, which could cause global temperatures to soar even more.
So environmental regulations aren’t making the planet warmer — that’s still caused by greenhouse gas emissions from humans — but the new regulations are eliminating a factor that until recently helped hide some of the warming, causing temperatures to temporarily spike even more.
“This could accelerate climate change because we can improve air quality faster than we can limit greenhouse gas emissions,” lead study scientist Andrew Gettelman of Pacific Northwest National Laboratory said in a statement.
This is not the first study to sound the alarm: other research groups have suggested that the 2020 restrictions have had a large impact on cloud cover, especially in areas with a lot of ship traffic. Relaxing these restrictions could lead to a significant reduction in global warming.
For example, a study published in June found that new shipping restrictions could cause an additional 0.16°C warming in just seven years, effectively doubling the planet’s average rate of warming since the last century.
But the exact figures are up for debate: A June study predicted more than twice the warming suggested by the new study, and scientists not involved in the study warned that its findings may have been exaggerated.
The new paper suggests that warming from shipping restrictions would be reduced, but acknowledges that there are many scientific uncertainties in its figures. Additional research based on more data on shipping routes and cloud physics around the world is needed.
Still, a growing body of research suggests that pollution controls could have a big impact on the rate at which the planet warms, even if the precise temperature response remains a matter of debate, meaning scientists need to take their effects into account when predicting future warming, the researchers say.
“As the world rapidly decarbonizes and reduces all anthropogenic emissions, including sulfur, it will become increasingly important to understand what the magnitude of the climate response will be,” Gettelman said in a statement. “Some changes could happen quite rapidly.”
Reprinted from E&E News Posted with permission from POLITICO, LLC. Copyright 2024. E&E News delivers news that matters to energy and environmental professionals.
