When you map carbon dioxide emissions in the atmosphere, the result looks very similar to population density -- which makes sense, since human activity is the overwhelming source of fossil fuel emissions. Yet one place where this is not true is over the oceans, where carbon dioxide is spreading out via shipping lanes and trade winds.

This map by Kennedy Elliott of The Washington Post uses data from the Earth System Research Laboratory of the National Oceanic and Atmosphere Administration to chart the levels of atmospheric carbon dioxide around the world. You can see that the eastern coast of North America, much of Europe and the Middle East, and China and India are all major contributors to atmospheric carbon dioxide.

But many of the world's biggest shipping routes also show up as surprisingly polluted, given their location far from land. The path that takes oil tankers through the Strait of Hormuz in the Middle East and the Strait of Malacca in Southeast Asia onto East Asia shows up brightly, as do the Trans-Atlantic and Trans-Pacific routes that connect the U.S. to East Asia and Europe.

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