Abstract
Abstract. Shipping is a growing sector in the global economy, and it contributions to global CO2 emissions are expected to increase. CO2 emissions from the world shipping fleet will likely be regulated in the near future, and studies have shown that significant emission reductions can be achieved at low cost. Regulations are being discussed for both existing ships as well as for future additions to the fleet. In this study a plausible CO2 emission reduction inventory is constructed for the cargo fleet existing in 2010, as well as for container ships, bulk ships and tankers separately. In the reduction inventories, CO2 emissions are reduced by 25–32% relative to baseline by applying 15 technical and operational emission reduction measures in accordance with a ship-type-specific cost-effectiveness criterion, and 9 other emission compounds are changed as a technical implication of reducing CO2. The overall climate and environmental effects of the changes to all 10 emission components in the reduction inventory are assessed using a chemical transport model, radiative forcing (RF) models and a simple climate model. We find substantial environmental and health benefits with up to 5% reduction in surface ozone levels, 15% reductions in surface sulfate and 10% reductions in wet deposition of sulfate in certain regions exposed to heavy ship traffic. The major ship types show distinctly different contributions in specific locations. For instance, the container fleet contributes 50% of the sulfate decline on the west coast of North America. The global radiative forcing from a 1 yr emission equal to the difference between baseline and reduction inventory shows an initial strong positive forcing from non-CO2 compounds. This warming effect is due to reduced cooling by aerosols and methane. After approximately 25 yr, the non-CO2 forcing is balanced by the CO2 forcing. For the global mean temperature change, we find a shift from warming to cooling after approximately 60 yr. The major ship types show significant differences in the short-term radiative forcing. For instance, the direct SO4 forcing from tankers is 30% higher than for container and bulk. The net long-term effects on RF are similar due to similar CO2 forcing. We assess an emission scenario where the reduction inventory is sustained on the fleet as it steadily diminishes over time due to scrapping and disappears in 2040. We find a net temperature increase lasting until approximately 2080. We conclude that changes in non-CO2 emission does matter significantly if reductions of CO2 emissions are made on the year 2010 cargo shipping fleet. In sum, we find that emission changes motivated by CO2 reductions in shipping will be beneficial from a long-term climate perspective, and that there are positive environmental and health effects identified as concentrations of key short-lived pollutants are reduced.
Highlights
Hydrology and Earth SystemShipping emissions have an impaSctcoinecnlicmeatse, human health and the environment (Eyring et al, 2010; Endresen et al., 2008; Buhaug et al, 2009), and to assess these impacts several studies have previously produced global ship emission i2n0v0e3n,to2r0i0es4,(C20o0rb7e;tEt yanriOdngKceoethalael.rn, 22S0000c53;,ie2D0na0lcs4ø;erEennderteasel.n, et al, 2009; Buhaug et al, 2009)
In four perturbation runs the emissions from the cargo fleet and three major ship types were changed from the baseline in accordance with Table 2 to assess the reduction inventory
The simple climate model (SCM) calculates radiative forcing from emissions or concentrations of source gases by applying standard parameterizations published in the literature
Summary
Shipping emissions have an impaSctcoinecnlicmeatse, human health and the environment (Eyring et al, 2010; Endresen et al., 2008; Buhaug et al, 2009), and to assess these impacts several studies have previously produced global ship emission i2n0v0e3n,to2r0i0es4,(C20o0rb7e;tEt yanriOdngKceoethalael.rn,, 22S0000c53;,ie2D0na0lcs4ø;erEennderteasel.n, et al, 2009; Buhaug et al, 2009). The IMO is working to develop regulations on CO2 (IMO, 2011) with the aim to reduce the climate impact from shipping, and significant efforts are directed towards finding technical, operational ways of mitigating CO2 emissions To this end, several studies have documented the measures available for CO2 reductions in shipping, ranging from operational changes, such as reduced speed, to alternative fuels, to technical measures (Skjølsvik et al, 2000; Buhaug et al 2009; Eide et al, 2009, 2011; UNEP, 2011). A reduction inventory for 2010 sequences for climate change initiated by particles, pro- is developed by estimating reductions of CO2, SOx, NOx viding a means for prioritizing policy and technology options and other relevant gases and particles resulting from assumed with different impacts They analyze the effect of zero emis- CO2 reduction policies. The effects of these concurrent emission changes are potentially important as it is well established that the emissions of other gases and particles impact climate in a significant way (Eyring et al, 2010)
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