The International Maritime Organization’s recent decision to adopt tighter emission rules for the global shipping fleet is a step in the right direction for an industry whose emissions have been practically unregulated. Ship emissions are blamed for 60,000 deaths worldwide each year — a serious public health threat.

The new rules, however, only address sulfur and nitrogen oxide emissions. Meanwhile, carbon dioxide emissions from the same ships remain a major, and often overlooked, contributor to global warming.

The world’s shipping fleet comprises 300,000 ships, each a city block in length, and transports 90 percent of the world’s trade. In 2007, the fleet emitted nearly twice as much carbon dioxide as all of America’s cars combined. If the fleet were a country, it’d be ranked as the sixth largest producer of CO2, between Japan and Germany.

Not to mention that these ships use the dirtiest fuel available, creating a high percentage of unusable sludge that must be burned.

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All in all, cargo ships are a major contributor to global warming, producing great amounts of the carbon dioxide that not only warms the planet but also leads to ocean acidification. The ships also generate black carbon, or soot, which is acutely dangerous to the Arctic. This particulate matter attaches itself to ice, causing the sun’s rays to be absorbed rather than deflected, melting the ice at an ever-faster rate. Faster-melting ice means more passable waters for ships in the Arctic, which means more black carbon, which means faster-melting ice …

No wonder the Arctic is warming at twice the rate of the rest of the planet.

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The International Marine Organization’s new rules would begin to cut ships’ sulfur oxide emissions in coastal areas by 2015. But there is one way that cargo ships could easily and instantly reduce their carbon footprint: simply slowing down.

  • The IMO has calculated that a speed reduction of just 10 percent by 2010 would result in a 23.3 percent reduction in emissions.
  • One shipping company, Hapag-Lloyd, found that slowing ships by 20 percent reduced fuel costs by half.
  • Slower cargo ships are roughly 10 times more fuel efficient than trucks and a hundred times more efficient than air transport — but as ship speeds increase, that advantage is wiped out.

In addition, shutting off ship engines in port — in other words, not idling a vehicle equivalent to 2,000 diesel trucks — would significantly reduce emissions. Better ship design that cuts water resistance is a technology that exists and that isn’t yet in common use. And, of course, there’s the dramatic — and not that far-fetched — concept of using kites to save fuel. These are all steps that could be taken much sooner than 2015.

The IMO’s new rules will reduce coastal emissions and protect public health, but they don’t begin to address the larger problem of ship emissions and global warming. The IMO has yet to demonstrate that it has the capacity to tackle this issue. In the meantime, the EPA should take up the slack. And if it doesn’t, well, I know of some conservationists who are already knocking on the EPA’s door.