I recall reading that cargo and fishing vessels (or is that all seafaring vessels? Or all ships and boats?) produce at least as much CO2 and particulates as the cars we drive, as the ships aren't nearly as clean as road vehicles.
I've no source for that, though, it was quite some time ago that I read it.
However, I also recall reading that boats produce a ton of emissions (I'm pretty sure it was a popular reddit post about how the huge oil tankers and shipping containers account for almost all ship-related emissions). One explanation: the maritime emissions may be underestimated due to the practice of ships using flags of convince. This website, and wikipedia and a few other sources, claim that the global contribution of maritime transportation to GHG/CO2 emissions is around 2% http://www.airclim.org/acidnews/new-figures-global-ship-emis...
2% of the total is still nothing to sneeze at, though. Since tankers and container ships are so big, it's likely that individual ships are some of the largest individual contributors to emissions. Maybe we should allow/subsidize these ships to use nuclear energy
If you trace that number used in the quick facts website to the report its data is based "Inventory of U.S. Greenhouse Gas Emissions and Sinks 1990–2015" you get the following explanation for the data Note that these totals include CO2, CH4 and N2O emissions from some sources in the U.S. Territories (ships and boats, recreational boats, non-transportation mobile sources) and CH4 and N2O emissions from transportation rail electricity. and An ongoing planned improvement is to develop improved estimates of domestic waterborne fuel consumption. The Inventory estimates for residual and distillate fuel used by ships and boats is based in part on data on bunker fuel use from the U.S. Department of Commerce. Domestic fuel consumption is estimated by subtracting fuel sold for international use from the total sold in the United States. It may be possible to more accurately estimate domestic fuel use and emissions by using detailed data on marine ship activity. The feasibility of using domestic marine activity data to improve the estimates will continue to be investigated.
Given this, I'm doubtful the report measures all cargo ships internationally.
No, this misleading stat refers to sulfur and soot emissions, not CO2. It's true that ships at sea burn a cheap sulfurous fuel, "bunker fuel", because there's nobody to inhale it out there. But it's misleading because people think this stat refers to CO2, which it doesn't. Ground transport produces far more CO2 than ships, which by weight are the most efficient way of moving anything.
That's true, but the sulfur emissions from ships do not have this effect. They actually have a slight negative greenhouse effect, because they reflect light in the upper atmosphere.
I've no source for that, though, it was quite some time ago that I read it.