By Paul Homewood
h/t sean2829
This was published in October 2022:
A global standard limiting sulfur in ship fuel reduced artificial “ship track” clouds to record-low levels in 2020. Pandemic-related disruptions played a secondary role.
Ship tracks, the polluted marine clouds that trail ocean-crossing vessels, are a signature of modern trade. Like ghostly fingerprints, they trace shipping lanes around the globe, from the North Pacific to the Mediterranean Sea. But in 2020, satellite observations showed fewer of those pollution fingerprints.
Drawing on nearly two decades of satellite imagery, researchers found that the number of ship tracks fell significantly after a new fuel regulation went into effect. A global standard implemented in 2020 by the International Maritime Organization (IMO) – requiring an 86% reduction in fuel sulfur content – likely reduced ship track formation. COVID-19-related trade disruptions also played a small role in the reduction.
Ship tracks were first observed as “anomalous cloud lines” in early weather satellite images acquired in the 1960s. They are formed by water vapor coalescing around small particles of pollution (aerosols) in ship exhaust. The highly concentrated droplets scatter more light and therefore appear brighter than non-polluted marine clouds, which are seeded by larger particles such as sea salt.
By capping fuel sulfur content at 0.5% (down from 3.5%), IMO’s global regulation in 2020 changed the chemical and physical composition of ship exhaust. Less sulfur emissions mean there are fewer of the aerosol particles released to form detectable ship tracks.
While analyzing 2020 data, the researchers found that ship-track density fell that year in every major shipping lane. Ship-based tracking data indicated that the COVID-19 pandemic played a role by decreasing global shipping traffic by 1.4% for a few months. But this change alone could not explain the large decrease in observed ship tracks, which remained at record-low levels through several months of 2021 (the most recent data analyzed). The researchers concluded that the new global fuel regulation played the dominant role in reducing ship tracks in 2020.
This reduction in pollution has undoubtedly had an upward effect on ocean temperature. The question is how much.
via NOT A LOT OF PEOPLE KNOW THAT
January 28, 2024 at 06:39AM
Iowa Climate Science Education 