[freebeard]

Susp... a little bird told me:

Imperial College London: Satellite tracking shows how ships affect clouds and climate

By matching the movement of ships to the changes in clouds caused by their emissions, researchers have shown how strongly the two are connected.

When ships burn fossil fuels, they release airborne particles containing various naturally occurring chemicals, including sulphur. These particles are known to modify certain types of clouds, which can affect climate.
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Aerosols are emitted from many sources, such as factories and cars, but it has been difficult to match these outputs with the influence on clouds, as there are many other factors at play.

However, with ship tracks, the relationship is more straightforward, enabling researchers to tease out the links between aerosols and clouds more easily.
[snip]
This shows that sulphate aerosols have the most significant impact on cloud formation, as opposed to other components of the ship exhaust, such as black carbon.

The result also means that a ship not in compliance with the regulations, by burning the current high-sulphur fuels without exhaust treatment, could be detected because it would create a measurable difference in the satellite-observed cloud properties.