It has long been known that the sulphur-laden heavy fuel oil used by ship’s engines is extremely polluting on a number of levels. Now new research suggests that this pollution increases the number of lightning strikes in the world’s busiest shipping lanes.
According to a report in New Scientist, Joel Thornton of the University of Washington in Seattle was looking at records of lightning strikes on the World Wide Lightning Network when he noticed two straight lines, with double the number of strikes compared to surrounding areas, in the eastern Indian Ocean and South China Sea.
These exactly matched the position of the busiest shipping lanes. After further research Thornton’s team concluded soot from the vessel’s exhausts is the culprit, acting as seeds around which water vapour condenses to form clouds.
Even though ships will invariably switch to a cleaner low sulphur fuel for the approach to port, they can still be responsible for significant local air pollution when in harbour. This is particularly evident in one of the UK’s largest ports, the south coast city of Southampton.
In addition to a busy container port and ro-ro port, as well as the nearby oil depot and refinery at Fawley, this is a popular destination for cruise ships, with the capacity for four or five vessels in harbour at any one time.
With each of these catering for up to 8,000 passengers and crew, the electricity generating requirements are of a similar magnitude to those of a small town. As a result, air quality in Southampton city suffers dramatically – it’s the worst of any city in the UK.