Unintended consequences

This is not the first time that this column has turned to the subject of the new International Maritime Organization (IMO) regulations on sulphur dioxide emissions from shipping and sulphur levels in bunker fuels, and it will probably not be the last, but a report published towards the end of last year by the Centre for International Climate and Environmental Research in Oslo (CICERO) has drawn attention to yet another paradox of our continuing obsession with sulphur-based emissions – the new regulations will increase global warming, and probably by a considerable amount.
The new IMO regulations, the first section of which will come into force in July, will cut the maximum sulphur content of shipping fuel to 3.5% in 2012 and 0.5 % by 2020. Special sulphur emission control areas (ECAs) around the coastlines of North America and in the Baltic and North seas have to achieve lower limits of 1% from this July and 0.1% by 2015. The shipping industry has been the last to face lower sulphur fuels – road transport and aviation already have regulations covering them. Indeed, sulphur levels in road fuels are down to parts per million in most of the major consuming regions, while in bunker fuels they are still at around 3 - 4%. As a result just a dozen or two large container ships can emit as much sulphur dioxide in a year as all of the developed world’s cars put together.
The aim of the IMO regulations will eventually – it is hoped – be a reduction in sulphur dioxide (SO2) emissions of up to 90%, and with them the resulting haze of sulphate particles that the SO2 is a precursor to. These particulates are known to cause lung and heart disease when they reach shore, and have been calculated to cause as many as 64,000 additional deaths worldwide every year, around 27,000 of them in Europe.
However, the particulates also reflect sunlight back into space, helping to partially mask the warming effects of greenhouses gases. Indeed, Nobel chemistry laureate Paul Crutzen has actually suggested that burning sulphur to produce sulphur dioxide in certain regions could actually be a way of mitigating global warming by ‘geoengineering’. At the moment, the cooling effect of SO2 emissions from ships actually far outweigh the warming effect of their CO2 emissions. Jan Fuglestvedt of CICERO has calculated that the net effect of the warming and cooling influences of ship emissions is that shipping currently neutralises about 7% of human-produced global warming. The removal of 90% of this sulphur over the next decade or so will thus serve to actually increase the effects of global warming by 6% or more.
A further complicating factor is that the impacts of the effects of CO2 and SO2 emissions are felt on very different timescales. The climatic effect of emissions from a ship at sea is initially dominated by the strong cooling influence of the SO2. As well as providing a direct shading effect, sulphate particles also act as nuclei around which water droplets form, making skies cloudier. However, this effect only lasts for a few days, until the ocean absorbs the SO2, and if it were not constantly being replenished, the warming effect of the ships' CO2 emissions would instead dominate, and continue to last for many decades.
Carbon dioxide emissions from shipping were left out of the 1997 Kyoto protocol because it is a complex issue. The IMO has long been planning action on CO2 emissions from ships – which represent around 3% of global emissions – but the need for coordinated international action means that this has been in abeyance since the failure of climate talks in Copenhagen in December. The issue of flags of convenience is a particularly vexed one, as two-thirds of the world's ships are registered in small non-industrial countries such as Panama and the Bahamas which do not have national CO2 emission targets. Treating the shipping industry separately from national targets would be possible, with its own emission ceiling, but developing countries argue that this spreads the burden unfairly between the developing and developed world. Still, there is huge potential to cut CO2 emissions from shipping. The Danish shipping line Maersk claimed earlier in the year that by making its container ships travel more slowly it had cut their fuel use, and hence carbon emissions, by 30%. Better designed engines, hulls and propellers could cut CO2 emissions by a further 15-20%.
It seems paradoxical to say the least that the IMO is able to make progress on cutting SO2 emissions and not CO2 emissions, in spite of the serious global difficulties that will ensue.