From Envirowiki

A ship is a large vessel that floats on water, intended to carry passengers or goods. Most world trade is done on ships, and shipping is thought to contribute 1.12 Gigatonnes of carbon dioxide, or 4.5% of total global carbon emissions^[1]

[edit] references

1. ↑ True scale of C0₂emissions from shipping revealed - John Vidal, environment editor, The Guardian, 2008 February 13