As environmentalists and scientists debate the effects of global warming and sea ice melting in the Arctic, shipping experts are quietly weighing how quickly — and how dramatically — international commerce might see a silver lining.

The Arctic has become a lighting rod of debate as Arctic nations, including Russia, Denmark, Canada and the Untied States, jockey to take advantage of highly lucrative natural resources beneath the fast-melting ice. About 90 billion gallons of oil and 1,670 trillion cubic feet of natural gas are buried underneath ice north of the Arctic Circle, according to the U.S. Geological Survey.

But melting sea ice would open new, previously treacherous and non-navigable passageways over Asia and North America, shortening some routes by thousands of miles. For example, access to the currently blocked Northwest Passage over North America would reduce a trip from Yokohama, Japan, to Rotterdam in the Netherlands to just 5,618 miles, according to Scott Borgerson, an ocean governance expert at the Council on Foreign Relations, a New York-based think tank.

That's a far cry from the popular 11,209-mile trip that requires ships to pass through the Panama Canal.

"It's not a matter of if but when," Borgerson said last week. "It's going to be sooner than later."

Scientists predict at some point over the next century ice will disappear from the Arctic during the summer, opening new passageways. Borgerson has said that could occur within the next several years. Walt Meier, a research scientist at the National Snow and Ice Data Center in Boulder, Colo., predicts 2025 at the earliest. Both acknowledge the extreme difficulty of predicting those patterns, however.

Estimates released around 2000 claimed the Arctic would see ice-free summers near the end of the century, but nearly all scientists now acknowledge warming has accelerated much faster than they predicted then, Meier says. It would also be nearly impossible to reverse that trend soon. Ice melting is a long, gradual process. Vast swaths of sea ice reflect solar heat back into space, but as the air temperature rises and that sea ice begins to thaw, the melting process speeds up, Meier says. With less sea ice reflecting heat, the ocean temperature rises, and the ice melts faster.

"Even if we stopped emitting CO2 today, which is quite unreasonable … what's already in that atmosphere will continue warming," Meier says.

Shipping companies aren't ready to redirect their fleets, says Joe Cox, president of the Chamber of Shipping of America, which represents shipping companies in the United States. The industry has established reliable routes through the Suez and Panama canals, for instance, and even if ice was completely gone tomorrow, the Arctic wouldn't be set up for easy navigation, he says. There are few working lighthouses, ports and data about treacherous obstacles and satellites haven't been used for commercial navigation there.

Ships might still face dangerous chunks of ice, requiring them to strengthen the hulls of their ships, Cox says. Those ships might also need to be insured at a higher cost, and despite the shortened distance, the trip might still not be economically feasible — and all that for a region that would only be ice-free for several months each year.

"There's a lot of questions about the Arctic, OK?" Cox says, chuckling. "I think companies will begin to take the risk of transiting the Arctic when they're assured they aren't going to be hitting any ice. … What point will there be an assurance that there's not going to be any non-navigable ice in the Arctic? And that, I bet a lot of scientists aren't going to be able to help."

Borgerson essentially agrees.

"There are people who put a lot more energy into the stock market and get it frequently wrong," he says.