But one climate-change expert still believes there is momentum for shipping to clean up its act.

Shipowners and operators should not think that pressure to limit or cut emissions of climate-changing gases from ships has vanished just because of the failure to reach political agreement in Copenhagen.

Shipping was not mentioned in the widely criticised "Copenhagen accord" but there remains momentum for the industry to clean up its act, according to climate-change expert Dr Anne-Marie Warris.

"I would be telling a shipowner today: don't assume this has gone away," she told TradeWinds.

Warris, the senior climate-change expert at UK classification society Lloyd's Register (LR) who spent the entire two weeks in Copenhagen as an observer of the drawn-out negotiations, acknowledges the process largely failed.

"We came to Copenhagen with the anticipation that we would have some agreement on bunker fuels that would leave the responsibility with the IMO [International Maritime Organisation]," she said.

"But we came out of Copenhagen with no political agreement; we came out of Copenhagen with no clear signal to business about whether they should or shouldn't continue to invest in clean technology; and also what might happen about market mechanisms.

"We also came out of Copenhagen with absolutely no deal on bunker fuels," she added.

Warris says fate and politics have dealt shipping a strange hand as it grapples with the issue.

"I stand by my analogy that we are playing poker but we ended up with some cards we hadn't quite expected. We don't actually know what the next hand is going to look like!" The International Chamber of Shipping (ICS) also says the outcome was disappointing and the way ahead uncertain.

"In particular, it remains unclear how the Kyoto Protocol principle of 'common but differentiated responsibility' (CBDR) should be reconciled with the important need for global rules on CO 2 [carbon-dioxide] reductions for the carriage of world trade - about 90% of which is carried by ships," the ICS said.

Despite the uncertainty, Warris sees a number of factors continuing to push the process forward.

On a political level, the Copenhagen accord throws open a whole new landscape with China showing muscle as an emerging super-power and Brazil, India and South Africa becoming more vocal.

"No deal in Copenhagen still means that we have got the Kyoto Protocol and Article 2.2, which leaves responsibility with Marpol Annex 1 and the IMO," she said.

The European Union (EU) has threatened action if Copenhagen and the IMO fail to deliver, while the US Senate is also debating bunker-fuel legislation.

One part of the US legislation would make the Environmental Protection Agency responsible for improving the efficiency of marine engines, while a second would demand that refineries deal with both domestic and international bunker fuels. "So while it isn't going to be an issue for shipowners to deal with - or the people who are responsible for paying the fuel bill - it is still going to be an effect for them," Warris said.

She adds that while there may not be agreement over a specific regulatory regime, market pressures from rising fuel prices could send a signal to cut emissions.

"This means looking at low-energy technology, not just for fuel saving but also for the long term. The use of the energy-efficiency design index may be encouraged by these market signals," Warris argued.

As the world emerges from recession, buyers of shipping services may also start to have an impact by choosing low-carbon businesses, she says.

"When we get out of the current economic downturn, people will be able to afford to pick a ship that has better environmental credentials," she added.

"It is going to stay a 'nice to have' rather than a 'must have', but it might become more of an influencing variable."