WASHINGTON D. C. — As hurricanes pummel the Caribbean and southern United States, new research is being published linking heavy shipping traffic to stronger storms.
Specifically looking at thunderstorms directly above two busy shipping lanes in the Indian Ocean and South China Sea, the compelling new study was based on mapping lightning strikes over a period of twelve years.
Showing a twofold increased incidence of lightning strikes over the shipping lanes, scientists say the research is the first of its kind and is especially convincing when it comes to linking human activity to storms.
“It’s one of the clearest examples of how humans are actually changing the intensity of storm processes on Earth through the emission of particulates from combustion,” says study lead author and atmospheric scientist Joel Thornton in a press release.
Other atmospheric scientists who weren’t involved in the study are likewise impressed with its results.
“It is the first time we have, literally, a smoking gun, showing over pristine ocean areas that the lightning amount is more than doubling,” says Daniel Rosenfeld, of the Hebrew University of Jerusalem. “The study shows, highly unambiguously, the relationship between anthropogenic emissions – in this case, from diesel engines – on deep convective clouds.”
Explaining the mechanism whereby ships affect storms, researchers say it seems particles from the ships’ exhaust cause smaller cloud droplets. This lifts the particles higher into the atmosphere, creating more ice particles and more lightning.
Adding further detail, the researchers explain that aerosols produced by combustion engines (such as soot, nitrogen, and sulfur compounds) act as nuclei for water vapor to form around. That is to say, just as water gathers on a cold glass, so it can gather on these tiny particles. These extra droplets boost cloud formation researchers say.
The basis of this new study came as NASA scientist and study co-author Katrina Virts noticed that sensors were picking up a peculiar pattern of lightning strikes. The strikes formed “a nearly straight line” across the Indian Ocean.
When she worked with colleagues to overlay lightning strike locations with shipping data, the research team found nearly twice as many strikes over major shipping routes.
“All we had to do was make a map of where the lightning was enhanced and a map of where the ships are traveling and it was pretty obvious just from the co-location of both of those that the ships were somehow involved in enhancing lightning,” Thornton says.
The study findings were published yesterday in the journal Geophysical Research Letters.