Welcome to post-panamax

Logically enough, the maximum possible size of ship it is possible to fit through the Panama canal is called a "panamax"—which happens to be 294.1 metres in length, 32.3 metres in width, 12.0 metres in draft and 57.91 metres in height, or around 65,000 tonnes displacement (if you're planning on taking cargo through the canal any time soon, you can read about the exact vessel requirements here).

Today, however, the buzzword for shipping is "post-panamax" (PPMX), which describes ships larger than at least one of these dimensions. And there are more and more of these around. Oil supertankers have existed since the Suez canal was closed between 1967 and 1975, a result of the Six Days War, but it wasn't until 1988 that container ships of PPMX dimensions first appeared, when five were built by American President Lines (APL). Now there are around 200 PPMX container ships in the world, and the number continues to grow. It was to the great relief of the shipping industry, then, that work finally began today on a long-awaited $5bn project to widen the Panama canal.

Shipping is big business—but you may be surprised at just how big it is, and how fast it's growing. As John Vidal recently noted in The Guardian, it is now responsible for transporting 90% of world trade; while carbon dioxide emissions from ships, which do not come under the Kyoto agreement or any proposed European legislation, could rise by as much as 75% in the next 15 to 20 years if current trends continue.

And it's very much "our" problem. According to the 2006 figures, European countries account for over 20% of world shipping tonnage, compared to a measly 1.4% by the United States. Tonne-for-tonne, shipping compares favourably to air and road transport; but the real debate centres on just how sustainable the transportation of such huge volumes of product across the world is in the long term. With almost every shipyard in the world currently working at maximum capacity, the move towards larger and larger vessels has something of a double edge.

And don't forget the Northwest passage, a potentially major linking route for shipping that's widening all by itself …