The climate deal made in Paris last November didn’t include cargo ships–despite the fact that shipping emits roughly as much climate pollution as the entire country of Germany (and more pollution than the 160 least-polluting countries to sign the agreement, combined).

A visualization from researchers at University College London and the digital journalism studio Kiln shows the scale of the challenge. At any given time, as many as 100,000 ships may be at sea, delivering iPhones from China to the U.S. or fish from Scotland to China. Roughly 90% of everything we buy arrives on a ship.

To make the map, the researchers pulled data from exactEarth, a company that tracks ships both by satellite and stations on land. By looking at each ship’s number–the equivalent of a license plate–they were then able to match it with technical details such as the type of engine it had and its speed, and use that calculate carbon emissions.

When they started work on the map, they had 2012 data available, but they say that the number of ships would be only slightly larger now. Over time, however, as populations grow and incomes rise around the world, ship traffic could increase so much that by 2050, it could make up as much as 17% of total greenhouse gas emissions in the world.

“If that’s happening in shipping, it’s going to cause a problem for all other sectors of the economy–unless we get shipping to decarbonize at the same time as everyone else,” says Tristan Smith, a lecturer in energy and transport at University College London and one of the creators of the map.

The researchers work on policy issues in shipping, often with the International Maritime Organization, and realized that most people know little about what goes on in the industry. “Being able to make this information a bit more accessible, make it more engaging and eye-catching, versus a 200-page report, which is what we normally produce–we thought that would be useful,” he says.