In his regular column, the BBC's environment analyst Roger Harrabin takes a tour of the world's biggest container ship to get a taste of the measures the shipping industry could take if it were serious about reducing its emissions of CO2.
IS SHIPPING SERIOUS ABOUT CUTTING EMISSIONS?
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Global shipping contributes about a billion tonnes of CO2. That's more than the entire economies of Germany or the UK.
Aviation lobbyists have gleefully highlighted the figures. They are a useful distraction from green assaults on the rise in aircraft emissions.
But the shipping industry indignantly rejects the comparison with aviation. The International Maritime Organisation says moving goods by ship is 80-100 times more efficient than by air.
Arguably the shipping industry has been complacent because it's demonstrably more efficient than its competitors already. Furthermore it doesn't have such effective cheer-leaders as aviation.
The Scandinavians are taking ships' emissions seriously, as you might expect with their traditions of seamanship and environmentalism. They took me on a tour of the Estelle Maersk, the world's biggest container ship, which is its owners claim is the most efficient in the world.
She is truly immense - 397m long, 56m wide, 21 stories high. It was impossible to get the TV camera to capture its scale. The biggest technical advance is above the gargantuan engine where internal funnels capture the waste heat and use it to drive two turbines which exert extra power on to the 131-ton propeller. Maersk say this saves about 9-10% of fuel.
There are other technical innovations: the engines are electronically-controlled; the giant hull shines with extra-slippery silicon paint; the refrigerated containers are partly cooled by water as well as electricity; automatic lighting controls are installed to make sure even small amounts of power aren't wasted (it all has to be generated by the diesel engine). (grab of engine avail)
There are operating changes, too. The bulbous bow is a now common feature on modern boats to increase stability and efficiency. Maersk have monitored how the bulb performs in different sea conditions and the captain now adjusts the trim by altering the balance of the ballast tanks to change its position in the water. (There is a grab of the bow from the On Demand vid)
A lot of work goes into optimising the course of the ship to save fuel. But the biggest saving is in reducing the speed of the vessel to around 10 knots where possible. This dramatically cuts fuel and therefore emissions. The engine designers warned that the engine might coke up it it was run too slowly, but this has not proved to be the case.
Maersk say that altogether they are managing to save about 25% of fuel/emissions against a comparable vessel. This is a massive benefit, bearing in mind that the annual fuel bill for the vessel runs to - brace yourself - $20 million.
I am sceptical about whether all these savings could be maintained during an economic boom. It's hard to imagine stalwarts of the just-in-time economy twiddling their thumbs at the warehouse waiting for the Estelle to amble through the Bay of Biscay at less than the speed of the Cutty Sark which did 16 knots on a good day. But some of the savings are clearly permanent.
Stig Neilsen, Maersk's environment chief, believes that in time, innovations in shipping might enable the industry to cut its emissions in half.
The question is what will force the pace of change? It'll be the main focus of conversation at World Maritime Day - the International Maritime Organisation's jamboree on 24 September.
There are two proposals on the table for the IMO. One from Germany, Norway and France is for a cap-and-trade system designed to limit emissions by making ship owners pay a price for their pollution - like the EU Emissions Trading Scheme. The backers say this would have to apply to all international shipping or rich country ship owners might just change flags to avoid the system.
This is meeting objections from emerging nations who say it runs counter to the UN Kyoto principle of "Common but Differentiated Responsibility" i.e. that developing countries get an easier ride whilst they are still developing.
The second proposal - from Denmark - is for a levy on shipping with proceeds going to poor nations to upgrade their fleets and also to adapt to the consequences of climate change. This has the advantage of ensuring that some of the proceeds from shipping are ring-fenced for the industry itself. It was designed to appeal to poorer countries and to be simple to implement.
But after complaints that it would not result in a cap on shipping emissions this proposal has been complicated with provision for a cap which would see an element of carbon trading.
The UK will announce its position soon. Bangladesh and vulnerable island states are pressing for a speedy decision that would cut emissions which threaten their lands. But neither proposal has a consensus and when I met the Chinese delegate a few months ago having a quick cigarette break outside the IMO, he told me there was no urgency. The conversation was very different from the urgent and positive tone I've heard from Chinese negotiators at the overall UNFCCC negotiations on climate change.
Is this a case of a traditional response from an economic ministry trying to avoid extra costs on its economy or a reflection of Chinese frustration that the West has not played its full part in meeting Kyoto targets? Talks at the IMO are coded, but I sense that emerging economies won't sign up to a shipping deal until they can see the results from the Copenhagen climate talks in December.