Researchers last week claimed that sulfur emissions from cargo ships are causing ocean and coastal pollution and affecting scientific understanding of global climate change. Scientists at Carnegie Mellon University in Pennsylvania and Duke University
in North Carolina said in a letter to the science journal Nature that ships are spewing more sulfur from their funnels than previously suspected which could be an important factor in solving the puzzle of global warming.
"You've got to consider ships explicitly if you are going to understand ocean chemistry which is a foundation for understanding atmospheric chemistry and climate change," said James Corbett, an engineer at Carnegie Mellon. In some coastal regions ships also have a significant impact on air quality, he added.
Regional sulfur emissions contribute to acid rain, which can pollute bodies of water. Emissions from ships are also involved in the formation of clouds over the oceans.
"Sulfur emissions have a large role in the formation of aerosols (tiny particles) on which water condenses to form clouds," said Spyros Pandis, who contributed to the study.
"The interactions of aerosols and clouds have been identified as one of the most important uncertainties in understanding the rate of climate change, or global warming, because clouds reflect energy and thereby reduce the net warming effect of long-lived greenhouse gases," he said.
The effect of aerosols has been difficult to quantify because they have a shorter lifetime in the atmosphere than greenhouse gases.
The researchers also showed that the emissions from ships were most evident in oceans in the Northern Hemisphere where heavy shipping occurs. Most oceans in the Southern Hemisphere, apart from the area surrounding Australia, are unaffected. Coastal cities receive the brunt of sulfur pollution from ships.
In a commentary on the research in Nature, Barry Huebert, of the University of Hawaii, said the study provides the first good argument for reducing sulfur pollution from shipping. "It is not very comforting to know that our waste is affecting an ever larger region. It is comforting, though, to see that the tools for making these assessments are getting sharper," he said.