Emissions today and tomorrow

The amount of black carbon emissions from shipping and the consequential climate impacts have been in the scope of scientific research lately. Both global and Arctic-specific studies have been carried out, focusing either on current levels (emission inventories) or on probable future levels (emission projec-tions). However, the estimates of the current and forthcoming BC emission levels are based on a multi-tude of definitions and assumptions. Thus a critical approach is always advisable.

An IMO-related inventory of shipping-based emissions (Corbett et al. 2007) estimates the annual BC emissions from the global maritime activities to be approximately 71 thousand tonnes in 2000—

2002. An alternative study (Lack et al. 2008) has produced somewhat higher numbers, ranging from 106 to 160 thousand tonnes in 2001. The best estimate of Lack et al. (2008) for BC emissions from global shipping (133 thousand tonnes per year) amounts to approximately 1.7 % of global BC from all sources.

However, the examination in question relies on a relatively broad definition of Light Absorbing Carbon (LAC), so that the results may not be entirely comparable. According to the authors of the study, LAC covers in fact both black carbon and brown carbon, as they both absorb light and thus affect the measurements done by utilizing a photoacoustic technique (Lack et al. 2008). In agreement with this, the emission factors used for LAC are slightly higher on average than the corresponding factors for mere BC in the Arctic-specific analysis of Corbett et al. (2010), for example.

There are various estimates concerning the BC fraction of PM, ranging from less than 5 to more than 40 % (Corbett et al. 2010). To be sure, there are numerous factors contributing to the composition of PM emissions and thus the share of BC. For example, engine type and fuel quality influence notably, and the essential roles of the applied BC definition and the measurement technologies chosen

10 The assessment is based on estimates of technology installation costs and time, additional operating costs due to possibly increased fuel consumption, and the presumed development of the interest and fuel price levels.

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ly must be borne in mind. Hence it is clear that no universal rate is appropriate, and quantifying such is not even reasonable.

According to Corbett et al. (2010), marine activities in the Arctic region produced a grand total of 1.2 thousand tonnes of BC emissions in 2004. This amounts to a share of few percentages of BC from global shipping, depending on the used estimates. Anyway, the relation of magnitudes is clear, and the role of the Arctic shipping is rather minor.

Peters et al. (2011) have also estimated the shipping-based BC emissions in the Arctic, though their study is not all-inclusive, as some sectors of shipping—such as marine activities related to tourism, fish-ing and local re-supply—are excluded from the numbers. They have evaluated a total amount of 1.2 thousand tonnes in 2004, which is practically same as the estimate of Corbett et al.

Both of the above-mentioned studies include also future projections of the shipping-based emis-sions in the Arctic, with the share of BC specified. The projections are based on the assumptions ex-plained earlier (in the section 4.4 in detail, and in section 5.1.2 more briefly), so that the results must be treated accordingly. In addition to the set of scenarios already introduced, Corbett et al. (2010) present also an option of maximum feasible reduction with respect to BC emissions (MFR). On the grounds of a feasible combination of improvements in technology performance and the implementation of certain abatement methods, BC emissions are assumed to decrease altogether 70 % in MFR. By including the

Fig. 35. The projected Arctic black carbon emissions in High Growth (top line images) and Business As Usual (bot-tom line images) scenarios. The predicted effects from implementation of abatement technology are presented in Maximum Feasible Reduction scenario (MFR, right-hand images). Source: Corbett et al. 2010.

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MFR option in their study, Corbett et al. enable a rather efficient comparison of different possible future developments, and thus the evaluation of the potential effects of unrestrained BC emissions.

In the Business As Usual scenario, shipping-based BC emissions in the Arctic (excluding the share of fishery) are estimated to be 1.4 and 5.0 thousand tonnes in 2050, in MFR and no-control scenario, respectively. In the High Growth scenario, the corresponding amounts soar to 5.0 and 17 thousand tonnes, respectively. The projected BC emissions from Arctic shipping in different scenarios—with and without abatements—are presented in Fig. 35, while the geographical distribution of the projected emis-sions in 2030 is shown in Fig. 36. (Corbett et al. 2010.)

The grand total of 17 thousand tonnes in the High Growth scenario with no control measures is of very remarkable magnitude, when for example compared to the estimates of current BC emissions from global shipping (that is, 71—160 thousand tonnes). It also means an increase of about 1 800 % in BC emissions from Arctic shipping from the 2004 level. However, the shipping-based BC emissions origi-nating in non-Arctic regions are presumed to increase as well, so that the relative proportion of Arctic emissions remains moderate.

The non-Arctic rates for BC emissions from shipping in 2050 are 393 and 710 thousand tonnes, in BAU and HiG scenarios, respectively (Corbett et al. 2010). Thus the share of Arctic BC emissions is at

Fig. 36. The geographic distribution of past (2004) (a) and projected (2030) black carbon emissions, both with (c) and without (b) the maximum feasible reduction (MFR) control measures. Source: Corbett et al. 2010.

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most around 2.5 % in 2050—that is, in the no-control HiG scenario. Nonetheless, it must be noted that the approximated amount of 710 thousand tonnes of BC emissions from global non-Arctic shipping in 2050 is in itself suspectible, as it relies on a constant annual growth of 3.3 %.

The analysis of Peters et al. (2011) results in more moderate amounts. Their estimate for BC emis-sions from Arctic shipping (excluding marine activities related to tourism, fishing and local re-supply) in 2050 is 3.0 thousand tonnes, implying an increase of about 150 % compared to the 2004 level. In their examination, the BC emission factor is presumed to remain the same, indicating a scenario with no abatement technologies implemented.

According to Winther et al. (2014), the BC emissions from Arctic shipping (excluding traffic on di-version routes) are projected to rise from 1.58 thousand tonnes in 2012 to 1.84 thousand tonnes in 2050, implying thus an increase of 16 %. The share of traffic using diversion routes in 2050 is presumed to increase the BC emission levels about 87 %. Hence, the total BC emissions from Arctic marine activi-ties are estimated to increase altogether 118 % from the 2012 level to 3.45 thousand tonnes in 2050.

Yet it must be emphasized that the rates from different studies are based on varying assumptions and definitions, so that the results are not entirely commensurable. For example, there is no established and thus unequivocal geographical definition of Arctic waters, and the coverage¹¹ of the inventories and projections varies. Despite such remarkable difficulties, a summarizing compilation of both estimated current and projected future emissions is presented in Fig. 37.