To add to my last response.
quote from another website regarding shipping. Meanwhile, want the grim punchline? There are now about 90,000 cargo vessels plying the waters globally. Not all emit as much as the hugest ships, of course. But if you assume the average ship is only one-tenth as bad as the giants, that means cargo vessels on the seas emit more than 500 times the total pollution of the world's vehicles.
After that, we don't quite know what to say.
SHIPPING BY NUMBERS (from The Guardian article)
The world's biggest container ships have 109,000 horsepower engines which weigh 2,300 tons.
Each ship expects to operate 24hrs a day for about 280 days a year
There are 90,000 ocean-going cargo ships
Shipping is responsible for 18-30% of all the world's nitrogen oxide (NOx) pollution and 9% of the global sulphur oxide (SOx) pollution.
One large ship can generate about 5,000 tonnes of sulphur oxide (SOx) pollution in a year
70% of all ship emissions are within 400km of land.
85% of all ship pollution is in the northern hemisphere.
Shipping is responsible for 3.5% to 4% of all climate change emissions
Yeah, we really need to clean up our owb's.