Studies have found that ships have a net cooling effect on the planet, despite belching out nearly a billion tons of carbon dioxide each year. That’s almost entirely because they also emit sulfur, which can scatter sunlight in the atmosphere and form or thicken clouds that reflect it away.
In effect, the shipping industry has been carrying out an unintentional experiment in climate engineering for more than a century. Global mean temperatures could be as much as 0.25 ˚C lower than they would otherwise have been, based on the mean “forcing effect” calculated by a 2009 study that pulled together other findings (see “The Growing Case for Geoengineering”). For a world struggling to keep temperatures from rising more than 2 ˚C, that’s a big helping hand.
And we’re about to take it away.
Read the MIT Technology Review story by James Temple - “We’re about to kill a massive, accidental experiment in reducing global warming.”
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