Our understanding of the climate and environmental impacts of shipping is far from complete, and there are many contentious issues in the negotiations on cuts in emissions.
About 80% of the total volume of world trade is transported by sea, and international shipping performs relatively well in environmental terms if we consider emissions per unit of goods transported or per kilometre. However, volumes of trade, shipping and emissions to air have all been growing rapidly in recent decades. Since 2000 in particular, these trends have to a large extent been driven by economic development in countries such as China and India. From 1986 to 2006, emissions from shipping more than doubled, and now account for 3% of anthropogenic CO2 emissions globally, or about 20 times Norway’s total CO2 emissions.
As a result of the global financial crisis and the decline in trade in the last quarter of 2008, shipping grew rather less in 2008 than in previous years. In the long term, however, various scenarios suggest that without further regulation, emissions from shipping will be 150-250% higher in 2050 than in 2007.
Cooling down and warming up
Because the shipping industry also generates large emissions of sulphur dioxide (SO2), its impact on global temperatures differs from that of other sectors. Sulphur dioxide forms sulphate particles, which have a direct cooling effect because they reflect sunlight. Sulphate particles also increase the concentration of water droplets in clouds; this makes them brighter, so that more sunlight is reflected back into space. Such indirect effects are the largest source of uncertainty in calculations of how emissions influence temperatures. The cooling effect of sulphur dioxide typically lasts for only a few decades, whereas the warming effect of CO2 lasts for centuries (see the figure). If emissions continue, CO2 will therefore accumulate in the atmosphere. Over time, the warming effect of CO2 will dominate. Until now, emissions from the shipping industry have had a net cooling effect, but if current levels of emissions continue, there will be a net warming effect after a few hundred years.
Almost 70% of pollutants from shipping are emitted within 400 km of land, causing local pollution problems in some coastal areas and large ports. It is estimated that between 20 000 and 104 000 premature deaths a year are caused by particulate pollution. Deposition of sulphates and nitrates also results in acidification and eutrophication in sensitive areas. In some coastal areas, for example in parts of Scandinavia, shipping accounts for 20-30% of deposition of these pollutants. In some of these areas, it is clear that the rapid increase in emissions from shipping is to some extent counteracting the effect that reducing emissions from land-based sources has had on the formation of ground-level ozone.
Regulation could increase global warming
In response to the pollution problems caused by shipping, the International Maritime Organization (IMO) adopted stricter controls on emissions of SO2 and nitrogen oxides (NOx) in autumn 2008. These include reducing the cap on the sulphur content of fuel from the current level of 4.5% to 3.5% in 2012 and then gradually to 0.5% in 2020. At present, the average sulphur content of fuel is 2.7%, so that the real effect will be felt when the last phase of the reductions is implemented – and this may be postponed. Calculations show that full implementation of these reductions will reduce the annual number of deaths that can be attributed to particulate pollution from ships by half. But on its own, a reduction in sulphur emissions will have a warming effect on the global climate. In other words, if sulphur emissions are reduced in line with the IMO decision, but other emissions remain at their current levels, emissions from shipping will have a net warming effect within only a few decades rather than a few centuries.
And what about climate-related regulation of emissions from shipping? Emissions from international shipping and aviation are not included in the Kyoto Protocol. IMO has been made responsible for regulatory measures for shipping. Because of the international nature of the industry, IMO traditionally treats all countries equally, whereas the Kyoto Protocol requires industrialised countries with a long history of emissions to make the largest cuts. The way IMO’s mandate is interpreted has prompted a great deal of debate, since two-thirds of the world fleet sails under foreign flags, and about 75% of the total tonnage sails under the flag of a developing country. The developing countries fear that they will lose a competitive advantage if greenhouse gas emissions from shipping are taxed or regulated.
There have also been proposals for an emission target to be set under the Climate Change Convention, and for IMO to be made responsible for administering and implementing emission cuts. The results of the climate negotiations at the Copenhagen summit were therefore awaited with some anticipation. A working group headed by Norway and Singapore held consultations on shipping and aviation, but did not reach agreement on a text that could be presented to the summit. In the absence of a global agreement, there are now strong signals that the EU and possibly the US will regulate emissions from shipping. The EU has indicated that it will aim to reduce CO2 emissions from shipping by 20% by 2020, probably by including them in the EU emission trading system. The US, is most likely to introduce a tax on emissions.
In addition, the shipping sector is considering the implementation of emission cuts on its own initiative. A recently published report on the second IMO greenhouse gas study identifies a number of technical and operational measures for reducing fuel consumption. These include design improvements, altering ship speed, using renewable fuels, and optimising voyages with respect to weather and currents. All in all, such measures could reduce CO2 emissions from shipping by between 25 and 75%.
Translation by Alison Coulthard
Denne artikkelen ble opprinnelig publisert i Magasinet Klima nummer 1, 2010