If shipping were a country, it'd be the 6th-biggest CO2 emitter

Cargo ships emit more CO2 per year than all of Germany (but a bit less than Japan). Emissions data for each country are 2016 totals, while the cargo ship emissions are an average of 2007-2012 data, from the UN International Maritime Organization. There are roughly 90,000 commercial cargo ships in the sea, and they carry roughly 90% of all internationally traded goods.