Feb. 14, 2008 - Maritime shipping is responsible for double the amount carbon dioxide emissions first estimated by the industry - and its carbon footprint will continue to grow as the business booms, Reuters reports. A new study by the U.N. International Maritime Organization estimates that global shipping released 1.12 billion metric tons of carbon dioxide in the atmosphere last year (about 3.5% of the planet's total emissions) and may increase 30% by 2020.

An industry estimate from 2000 had pegged emissions at 1.4% of total greenhouse gases. A figure of 3%-5% was considered a "worst-case scenario."

The International Chamber of Shipping (ICS) is downplaying the new numbers. "In essence whether its 2%, 3.5%, or 5% is almost immaterial because the industry recognizes that it's part of the problem and it's got to play its part in delivering solutions," says ICS secretary Simon Bennett. "[Shipping] is responsible for running the world economy, so it's no surprise that we do produce significant emissions and it's been down to the scientists to come up with estimates of what the percentage might be."

Maritime shipping, which transports more than 90% of global trade goods, generates a trillion dollars in annual revenue.