The first survey of emissions from commercial shipping has shown them to be big dirty beasts. Daniel Lack from the National Oceanic and Atmospheric Administration (NOAA) measured emissions from ships in the Gulf of Mexico, Galveston Bay and the Houston Ship Channel. He estimated from this that globally ships emit 0.9 teragrams of particle pollution annually. (Press release)
But the resulting effect on the climate seems confusing. As reported by Bloomberg, the particulates, including sulfates, organics, cloud condensation nuclei, that commercial carriers spew out act to cool the atmosphere. This effect, the authors say, outweighs the warming effect of ships’ carbon dioxide emissions five-fold. (Bloomberg story).
Lack looked at differences between newer, cleaner low-sulfur fuel and the standard high-sulfur fuels. Sulfur makes up half of the particulates. “Fortunately, engines burning ‘cleaner,’ low-sulfur fuels tend to require less complex lubricants. So the sulfur fuel regulations have the indirect effect of reducing the organic particles emitted,” said Lack’s co-author James Corbett from the University of Delaware.
Shipping has been a little overlooked so far in global environmental budgets, but here is yet more evidence that ships are major sources of pollutants. (That is, of course, unless they all switched to using giant kites to propel themselves.)