Slashing sulfur in shipping fuel reduces air pollution at sea, according to NASA AI
According to a NASA AI model, reducing sulfur in shipping fuel reduced sea-level air pollution to the lowest levels this century in 2020. Of course, the COVID-19 pandemic aided in this as well.
The International Maritime Organization's (IMO) rule limiting the sulfur content of fuel oil for ships traveling outside emission-control areas went into effect two years ago. The restriction was expected to reduce sulfur oxide emissions by 77%, or 8.5 million metric tonnes. The carcinogenic gas raises the risk of acid rain and can cause respiratory, cardiovascular, and lung disease.
According to a NASA study, the IMO 2020 policy—and lower levels of shipping traffic during the early stages of the COVID-19 pandemic—reduced shipping air pollution to the lowest levels since tracking began nearly 20 years ago. Researchers made an AI model to find shipping tracks in images taken by NASA's Earth-observation Aqua satellite's Moderate Resolution Imaging Spectroradiometer (MODIS) instrument from 2003 to 2020.
"We cannot begin to understand this problem without this kind of complete and large-scale sampling of ship tracks," Tianle Yuan, an atmospheric scientist at NASA's Goddard Space Flight Center and the University of Maryland, said Tuesday. The findings of the study were recently published in Science.
Initially, the images revealed what the model identified as "anomalous cloud lines." These clouds form when pollutant aerosols emitted by ships combine with water vapor. The concentrated droplets scatter more light and appear brighter than other types of sea clouds, which contain larger salt particles.
The model helped researchers figure out that ships started putting out less pollution in the air in 2020, when the amount of sulfur in fuel was capped.
According to the paper, "ship-track density experiences strong decreases in every detected major shipping lane compared to climatology and reaches record lows in the nearly 20-year data record."
Other shipping lanes, with the exception of the trans-Pacific and trans-North Atlantic shipping lanes, are no longer discernible. When compared to the climatological mean, the annual mean ship-track density decreases by 50% or more in five major shipping lanes. When compared to 2019, the decline is even more pronounced. "
Global shipping traffic fell by 1.4 percent during the COVID-19 pandemic and remained low in 2021, despite the fact that fewer vessels did not account for the large drop in detected shipping tracks.According to the researchers, the IMO 2020 fuel regulation had a greater impact on reducing air pollution.
They were also able to trace popular shipping routes across Asia and America at various times, such as the drop in global trade after the 2008 financial crisis. There were two other drops in Asian shipping traffic between 2014 and 2016, when China imported and exported fewer resources.
"Ship tracks are excellent natural laboratories for studying the interaction of aerosols and low clouds, as well as how this affects the amount of radiation that Earth receives and reflects back to space," Yuan said. "That is a significant uncertainty in terms of what drives the climate right now."