Map of global commercial shipping routes.
B.S. Halpern (T. Hengl; D. Groll) / CC BY-SA 3.0

It takes 5 million barrels of fuel per day to move commercial ships across the routes shown on this map. Added up over the course of a year, international shipping emits more than 800 million tons of carbon dioxide or its equivalent in other greenhouse gases—11 percent of the total emissions from the transportation sector.