Article pubs.acs.org/est
Climate Penalty for Shifting Shipping to the Arctic Jan S. Fuglestvedt,† Stig Bjørløw Dalsøren,*,† Bjørn Hallvard Samset,† Terje Berntsen,†,‡ Gunnar Myhre,† Øivind Hodnebrog,† Magnus Strandmyr Eide,§ and Trond Flisnes Bergh§ †
CICERO, Center for International Climate and Environmental Research-Oslo, Oslo, Norway University of Oslo, Department of Geosciences, Oslo, Norway § DNV GL, Høvik, Norway ‡
S Supporting Information *
ABSTRACT: The changing climate in the Arctic opens new shipping routes. A shift to shorter Arctic transit will, however, incur a climate penalty over the first one and a half centuries. We investigate the net climate effect of diverting a segment of Europe−Asia container traffic from the Suez to an Arctic transit route. We find an initial net warming for the first one-and-a-half centuries, which gradually declines and transitions to net cooling as the effects of CO2 reductions become dominant, resulting in climate mitigation only in the long term. Thus, the possibilities for shifting shipping to the Arctic confront policymakers with the question of how to weigh a century-scale warming with large uncertainties versus a long-term climate benefit from CO2 reductions.
■
INTRODUCTION The melting of Arctic sea ice may open new shipping routes between Europe and Asia.1−7 The Arctic route is shorter relative to the traditional Suez route and could result in significant fuel saving and reductions in CO2 emissions. In addition to CO2, ships emit a number of gases and aerosols with both warming and cooling effects operating on a broad range of time and spatial scales.8−10 The climate impacts of these components depend strongly on location and timing of emissions.11 In this study, detailed modeling of chemical, radiative, and temperature responses have been performed to quantify the net climate impact caused by new emissions in the Arctic and reduced emissions via the Suez route. We use Arctic shipping emission inventories3 for 2030 and 2050 with a gradual increase in container traffic on a new Arctic route between Europe (Rotterdam) and Asia (Yokohama). The Arctic transits occur in the period July−November when it is expected to be feasible and economically profitable to use the northern route.3 The advantage of the northern route compared to the traditional Suez route is shorter (43%) distance and travel time resulting in less fuel consumption (Figure S1, Supporting Information) and emissions for the same volume of transported cargo. This is, however, somewhat compensated by increased fuel consumption per kilometer to break through ice, especially in 2030. Applying the optimal Arctic route reduces the travel time by 37% in 2030 and 43% in 2050, while the fuel consumption is reduced by 29% and 37%. The total whole-year fuel consumption from shipping between Rotterdam and Yokohama is reduced by 10% in 2030 and 16% in 2050. Similar factors apply for relative reductions in emissions to air of chemical constituents (CO2, NOX (nitrogen © 2014 American Chemical Society
oxides), SOX (sulfur oxides), NMVOCs (non-methane volatile organic compounds), CO, black carbon (BC), and organic aerosols (OA)) as we assume identical emission factors for the components along the two routes.3 The rationale is that current ratified emission regulations will apply globally as intended. We do not assume differences that would appear if parts of the routes become situated in emission control areas (ECAs). A traffic shift from the Suez to the Arctic could then lead to smaller or larger reductions of NOX and SOX emissions dependent on which route is subjected to ECA regulations. The scenario from Peters et al.3 estimates a transported Rotterdam−Yokohama (R−Y) container volume of 1.4 MTEU (million twenty-foot equivalent unit) and 480 trips during 100 days of Arctic transit in 2030. This is 36% of the total volume for the R−Y route and 8% of the estimated container traffic between Europe and Asia. In 2050, the volumes transported during the 120 days of Arctic transit season rise to 2.5 MTEU corresponding to 850 journeys. This is 45% of the potential for the R−Y route and 10% of the container traffic between Europe and Asia. Due to the shorter sailing distance the cargo volume transported per day is higher in the Arctic. Therefore, moving this transport to the Arctic also induces emission decreases in the Suez route outside the Arctic transit season (Figure S2, Supporting Information). Received: Revised: Accepted: Published: 13273
May 14, October October October
2014 25, 2014 27, 2014 27, 2014
dx.doi.org/10.1021/es502379d | Environ. Sci. Technol. 2014, 48, 13273−13279
Environmental Science & Technology
■
Article
METHODS AND MODELS As a baseline emission scenario in the model simulations we use the RCP8.5 scenario12 for 2030 and 2050 nonship anthropogenic emissions and the RETRO inventory13 for year 2000 for natural emissions. In the Arctic, we replace the petroleum emissions in RCP8.5 with the emission inventory for 2030 and 2050 from Peters et al.3 We also include shipping related to this activity (both transport of products and supply of offshore installations) from Peters et al.3 Other shipping emissions for 2030 and 2050 are included at the same level as the 2004 inventory from Dalsøren et al.14 However, we take into account changes in emission factors of SOX, OA (correlated with SOX), and NOX due to existing IMO regulations. In the Arctic scenario, 36% (2030) and 45% (2050) of the R−Y container trade volume diverts from the traditional Suez route in the baseline inventory to a new Arctic transit route. The basic principles for the diversion are described in the introduction, and further details are given in Peters et al.3 The model simulations discussed in the Results and Discussion used the baseline scenario and the Arctic scenario for 2030 and 2050, respectively. Extra simulations performed to obtain additional insights are discussed in the Supporting Information. The different atmospheric conditions and sensitivity to emissions at high and low latitudes11,15 will determine the resulting climate impacts of near-term climate forcers (NTCF). In contrast, the impacts of CO2 and other long-lived greenhouse gases do not depend on emission location. Using a chemical transport model (CTM) and an offline radiative transfer model (RTM) we have calculated radiative forcing (RF) from shifting R−Y transport from Suez to the Arctic as described above. In addition to CO2, we include effects of NOX, CO, and NMVOCs on tropospheric ozone and methane as well as sulfate, nitrate, OA, and BC (in air, semidirect, and deposited on snow/ice) aerosols. The OsloCTM2 model was used to calculate the tropospheric distributions of 85 chemical species, among them hydrogen-, oxygen-, nitrogen-, and carbon-containing gases and also sulfate-, nitrate-, primary organic-, secondary organic-, black carbon- (BC), and sea-salt aerosols. Simulations were performed in T42 resolution (2.8° × 2.8°) with 60 vertical layers. Meteorological data for 2006 from the Integrated Forecast System (IFS) model (from ECMWF) were used in all simulations. The results do not account for the effect of future climate change on meteorology. However, the impacts of future sea ice conditions on surface dry deposition were included as we used the same gridded ice data as those used in the calculations of future Arctic ship emissions.3 The gas and aerosol schemes are described in refs 15−21. The model was used in previous studies on impacts of Arctic shipping.15,22 Modeled distributions of ozone and ozone precursors in coastal regions were evaluated and compared to observations and other models in former ship impact studies.23−26 The atmospheric distributions of ozone and aerosols in 2030 and 2050 were fed into a radiative-transfer model17 to calculate RF.27 The model is based on the DISORT radiative-transfer scheme28 and uses eight multiple-scattering streams and four shortwave spectral bands for aerosol simulations. For O3 RF calculations the same radiative transfer is applied but with a spectral resolution of 5 nm, and a broadband thermal infrared scheme is adopted29 with stratospheric temperature adjustment included. Temporal and spatial resolutions were the same as for OsloCTM2 for aerosols, whereas monthly mean data were used
for ozone. The optical properties of aerosols in the model are discussed in ref 30. Radiative forcings of direct and indirect aerosol effects were calculated as the difference in top-ofatmosphere energy flux between a simulation with all components at 2030 or 2050 levels and one that has one component changed to 2004 levels. To further study the differences in RF between, e.g., two 2030 conditions (for example, Suez and Arctic shipping), we take the difference between RFs for each component calculated using the above method. The radiative-transfer scheme was further used for calculating the effects of BC deposition on snow/ice albedo.19 The first indirect aerosol (cloud albedo) effect was calculated by estimating cloud droplet number from an empirical relationship with aerosol concentration31,32 and calculating the difference between aerosols at 2030 and 2004 levels as for the direct aerosol effect. See Ødemark et al.15 for details. The RF calculations use the same meteorological and ice data as the CTM. The semidirect aerosol effect for BC has been calculated using the National Center for Atmospheric Research (NCAR) Community Earth System Model (CESM1.0.4) (see the Supporting Information and Hodnebrog et al.33) with prescribed monthly mean BC concentrations from OsloCTM2. Aerosol-cloud interactions beyond the cloud albedo effect are not considered in this study. In general, this effect would enhance the cloud albedo effect; however, there is limited observational evidence indicating that its impact is of significant magnitude.34 We used the approach described in Berntsen et al.35 and Myhre et al.29 to calculate the RF from methane and associated ozone and stratospheric water vapor changes. We adapted the calculation of ozone changes from recent findings27 suggesting that the ozone RF equals half of the methane RF. The RF values from this method apply for the time when the perturbations have reached equilibrium conditions. For the development of CO2 levels and RF we have used the impulse response function from36 and radiative efficiency from AR5.27 We use the estimates of RF as input to a simple 2-box analytical climate model based on the approach of Berntsen and Fuglestvedt9 to calculate global mean temperature change by component over time. The climate model has a coupled atmosphere-mixed ocean layer box and a deep ocean box, allowing also for the long-term climate response; see Berntsen and Fuglestvedt9 for details. The RF is implemented as pulses decaying corresponding to the atmospheric residence time of each component. The model assumes an equilibrium climate sensitivity of 0.9 K/W/m2. The value is well within the range of IPCC AR537 estimates for radiative forcing and temperature change from a doubling of atmospheric CO2 concentration.
■
RESULTS AND DISCUSSION Figure 1 shows the calculated global annual RF, by component, and total non-CO2 and CO2 RF for 2030 and 2050. Shifting parts of the shipping from Suez to the Arctic route, i.e., reducing emissions at lower latitudes and introducing new emissions in the Arctic, gives positive net RFs from changes in non-CO2 components of 0.25 [0.07, 0.46] and 0.35 [0.05, 0.68] mW/m2, for 2030 and 2050, respectively. The large positive RFs from sulfate and the indirect effect of aerosols result from a strong positive RF from decreasing emissions along the Suez route, in addition to a small positive RF from increasing Arctic emissions. Despite different signs of the emission changes in the two regions the RF from both perturbations are positive. For the Suez route, high insolation 13274
dx.doi.org/10.1021/es502379d | Environ. Sci. Technol. 2014, 48, 13273−13279
Environmental Science & Technology
Article
for difference in sign of semidirect RF between these regions. However, the estimated uncertainty for the semidirect effect is larger than for any of the other RF mechanisms investigated here. The regional shift of emissions of NOX, CO, and NMVOCs leads to significant changes in ozone and methane. When the emissions decrease along the Suez route less ozone precursors are transported to high altitudes by vigorous convection during summer when the Intertropical Convergence Zone in the Indian Ocean moves north of the equator close to the route. At these altitudes and latitudes with efficient ozone production and long ozone lifetime this results in rather large reductions of ozone. Since the changes occur in the subtropics/tropics (Figure 2e) at high altitudes the impact of ozone changes on RF is relatively large. The impact of Arctic shipping on ozone is much smaller due to lower surface temperature and lower temperature gradient which influences the longwave forcing, as well as less sunlight which influences the shortwave forcing. The overall effect of a strong Suez signal and a weak Arctic signal is a strong net negative ozone RF (Figure 1). The RF due to methane and changes in associated components is weaker and of opposite sign to that from ozone. Decreased NOX emissions along the Suez route efficiently reduce OH, leading to enhanced methane RF. The changes in organic aerosols (OA) and nitrate are small and only give minor contributions to the total RF. Except for methane and methane-induced O3 and stratospheric H2O changes, the RF values calculated for the NTCFs reflect instantaneous changes (i.e., occurring on a time scale of days to months). CO2, however, has a response time of centuries,36 which means that the atmospheric levels are determined by emission history. Thus, assumptions about emission pathway are needed to quantify its total climate impact. For the R−Y Arctic transit route we have assumed linear trends from zero emissions in 2025 up to 2030 levels and further to 2050. The RF from CO2 is −0.009 [−0.008, −0.012] W/m2 in 2030 and −0.045 [−0.036, −0.057] W/m2 in 2050. This is small compared to the NTCF, but this gas has larger effects on longer time scales (see below). Direct emissions of CH4 and N2O are small and the RFs are found to be negligible. For the assumed linearized emission scenario described above, and with constant emissions after 2050, we calculated the response in global-mean temperature (Figure 3) over two centuries to capture the various time scales of the different components. Shifting shipping from Suez to Arctic initiates responses of very different magnitudes and signs. A group of small warming effects (nitrate, OA and stratospheric H2O) can be seen in Figure 3. BC on snow/ice (accounting for a high climate sensitivity to RF34) has a maximum warming effect around 2040 and declines thereafter due to reduced ice cover. After this time, the warming from methane, primary mode O3, sulfate, semidirect effect of BC and indirect aerosol effect dominates. Strong cooling effects from changes in direct aerosol effect of BC and O3 are found. In a separate category, we find the negative CO2 response which steadily grows larger. The net effect of all these contributions is a warming for the first oneand-a-half centuries, which thereafter switches to cooling due to the long response time and dominant effect of CO2. As shown in the inset, accounting for uncertainties (5−95%), based on uncertainties in RF from NTCF (Figure 1), in CO2 response36 and climate sensitivity (see the Supporting Information), shows that the warming period may last up to several centuries but
Figure 1. Effects in terms of global annual RF by component of shifting shipping routes from the Suez to the Arctic route (upper) and uncertainty distributions (lower) for 2030 and 2050. Uncertainty bars are given for 5−95% ranges. OA = organic aerosols, s.l. = short-lived, p.m. = primary mode.
and efficient reflection by sulfate and clouds explain the strong RF in vicinity of the Suez route (Figure 2a,c). In the Arctic there is, as expected, a negative RF over the oceans (in the vicinity of the route) due to enhancement of sulfate in the marine boundary layer (MBL). However, a more than compensating positive RF appears over northern America and Asia (Figure 2a,c). This occurs due to enhanced MBL oxidation of SO2 from nonship sources and efficient removal of resulting sulfate in the MBL, implying less sulfate transported to the free troposphere (see the Supporting Information). While the sign of the net RFs from sulfate and the indirect effect of aerosols are found to be positive and relatively large (Figure 1) we also estimate a large uncertainty range. When shipping via Suez is reduced and introduced in the Arctic we find a reduction in the net direct aerosol effect of black carbon (BC) (Figure 1). The main reason is that BC emitted into the Arctic atmosphere reaches lower altitudes and has shorter lifetime. On the other hand, BC emitted from Arctic shipping has a much larger effect when deposited on snow/ice (Figure 2b,d and Figure S5, Supporting Information); thus the shift to the Arctic causes a net positive global RF from BC on snow/ice. Due to the gradual reduction in Arctic sea ice, the RF from BC on snow/ice is smaller in 2050 than 2030. Both the RFs for direct aerosol effect of BC and BC on snow/ice have quite large uncertainties (Figure 1). For BC the main changes occur in the vicinity of the ship routes (Figure 2b), especially in the Arctic where mixing between the MBL and the free troposphere is rather inefficient. The semidirect effect of BC is negative from the Suez route and positive from the Arctic route. From moving shipping north, we find a positive net RF due to the semidirect effect, dominated by a reduction in negative forcing from the Suez region. The semidirect effect is strongly dependent on altitude,38 and differences in altitude of the BC perturbations from the Suez and Arctic routes are a main cause 13275
dx.doi.org/10.1021/es502379d | Environ. Sci. Technol. 2014, 48, 13273−13279
Environmental Science & Technology
Article
Figure 2. Effects in terms of annual RF of shifting shipping from the Suez to the Arctic route (in 2050) for sulfate (a), BC (direct effect) (b), indirect effects of aerosols on clouds (c), BC deposited on snow/ice, (d) and short-lived ozone (e). Note that the units on the color scales are different.
from the shorter route. To illustrate the long-term effect we simply assumed constant emissions after 2050. With a further retreat of sea ice after 2050 the difference in emissions compared to the Suez route would probably grow but not necessarily proportionally to the number of Arctic transits since fuel consumption and emissions depend on season and ice conditions. The chemical and physical responses in the atmosphere are dependent on season and strength of emission perturbation. When these parameters change a nonlinear response cannot be ruled out but it is likely that the effect of growing traffic along the route would be an augmentation of our obtained climate signal (sign of temperature change and evolution over time). With less ice Arctic transits from Western Europe to eastern Asia could start between a set of different destinations and via several Arctic travel routes. Changes in emissions compared to
also that the possibility of a net cooling effect from the start cannot be ruled out. We focused on global mean RF and temperature in this study. Recent studies show how regionally different RF patterns cause different regional patterns of temperature response,35,39−41 and further studies are needed to assess impacts of shifting shipping routes. Sulfate and black carbon with both a direct, semidirect, and strong snow/ice albedo effect are key components in the assessment of shifting shipping routes to the Arctic. In this study, we focus on only one shipping route where the conditions likely are profitable for Arctic transit shipping already in the near future (around year 2030). The climate signal is therefore small. However, our results show how inclusion of the full set of emissions is crucial as it make a significant modification to the effect of a CO2-only reduction 13276
dx.doi.org/10.1021/es502379d | Environ. Sci. Technol. 2014, 48, 13273−13279
Environmental Science & Technology
Article
Figure 3. Development in global mean temperature change by component and as total net effect including uncertainties. OA = organic aerosols, s.l. = short-lived, p.m. = primary mode. The inset figure shows the total net effect (black line) and uncertainties (5−95% confidence range as black dotted lines).
costs and higher CO 2 emissions with its long-term consequences and the cooling from NTCF versus the Arctic route with a century-scale warming but large inherent uncertainties due to NTCF.
the Suez route would then depend on sailing distance (destinations and route choice in the Arctic), season, and ice conditions. As long as we consider substitution of Suez transport with Arctic transits it is reasonable to assume approximately linearity in responses and use our results for the single Arctic route as an analogue. For substitution of other intercontinental routes (e.g., Panama, Southern Africa, Southern America), additional studies are needed since different physical conditions result in changed sensitivity of the climate response to emission perturbations. Emissions from shipping induce a series of climate effects, with RF of both signs. Here we have shown that reducing emissions at low latitudes and introducing emissions at higher latitudes adds complexity to assessments of climate impacts of future shipping routes. Thus, also in this case, the effects of NTCF need to be accounted for in addition to CO2. If the transient warming due to a movement is seen as unwanted, thenimplicitlythe negative RF by NTCF from shipping caused by the current R−Y Suez transits is valued as beneficial and, thus, as a form of “passive geo-engineering”. It is not obvious how negative RF should be considered in climate strategies.42 A question that needs to be addressed by policymakers is how to weigh the Suez route with higher fuel
■
ASSOCIATED CONTENT
S Supporting Information *
Additional information on applied methods. Uncertainty calculations. Results from additional model runs. Figures S1− S5. This material is available free of charge via the Internet at http://pubs.acs.org.
■
AUTHOR INFORMATION
Corresponding Author
*E-mail: [email protected]. Tel: +4745472629. Author Contributions
J.S.F.: Developed idea and project leader, analysis, article outline, and writing. S.B.D.: CTM calculations, RF calculations, analysis, article outline and writing. B.H.S.: RF calculations, analysis and writing. T.B.: Developed idea and project, analysis, temperature response, and uncertainty calculations and writing. G.M.: Developed idea and project, RF calculations, analysis, and writing. Ø.H.: Calculations of semidirect effect of BC. 13277
dx.doi.org/10.1021/es502379d | Environ. Sci. Technol. 2014, 48, 13273−13279
Environmental Science & Technology
Article
(16) Myhre, G.; Grini, A.; Metzger, S. Modelling of nitrate and ammonium-containing aerosols in presence of sea salt. Atmos. Chem. Phys. 2006, 6, 4809−4821. (17) Myhre, G.; Berglen, T.; Johnsrud, M.; Hoyle, C.; Berntsen, T.; Christopher, S.; Fahey, D.; Isaksen, I.; Jones, T.; Kahn, R.; Loeb, N.; Quinn, P.; Remer, L.; Schwarz, J.; Yttri, K. Modelled radiative forcing of the direct aerosol effect with multi-observation evaluation. Atmos. Chem. Phys. 2009, 9, 1365−1392. (18) Skeie, R.; Berntsen, T.; Myhre, G.; Tanaka, K.; Kvalevag, M.; Hoyle, C. Anthropogenic radiative forcing time series from preindustrial times until 2010. Atmos. Chem. Phys. 2011, 11, 11827− 11857. (19) Skeie, R.; Berntsen, T.; Myhre, G.; Pedersen, C.; Strom, J.; Gerland, S.; Ogren, J. Black carbon in the atmosphere and snow, from pre-industrial times until present. Atmos. Chem. Phys. 2011, 11, 6809− 6836. (20) Berglen, T.; Berntsen, T.; Isaksen, I.; Sundet, J. A global model of the coupled sulfur/oxidant chemistry in the troposphere: The sulfur cycle. J. Geophys. Res.: Atmos. 2004, 109, 27. (21) Hoyle, C.; Berntsen, T.; Myhre, G.; Isaksen, I. Secondary organic aerosol in the global aerosol - chemical transport model Oslo CTM2. Atmos. Chem. Phys. 2007, 7, 5675−5694. (22) Dalsoren, S.; Samset, B.; Myhre, G.; Corbett, J.; Minjares, R.; Lack, D.; Fuglestvedt, J. Environmental impacts of shipping in 2030 with a particular focus on the Arctic region. Atmos. Chem. Phys. 2013, 13, 1941−1955. (23) Endresen, O.; Sorgard, E.; Sundet, J.; Dalsoren, S.; Isaksen, I.; Berglen, T.; Gravir, G. Emission from international sea transportation and environmental impact. J. Geophys. Res.: Atmos. 2003, 108, 22. (24) Dalsoren, S.; Endresen, O.; Isaksen, I.; Gravir, G.; Sorgard, E., Environmental impacts of the expected increase in sea transportation, with a particular focus on oil and gas scenarios for Norway and northwest Russia. J. Geophys. Res.: Atmos. 2007, 112. (25) Dalsoren, S.; Eide, M.; Myhre, G.; Endresen, O.; Isaksen, I.; Fuglestvedt, J. Impacts of the Large Increase in International Ship Traffic 2000−2007 on Tropospheric Ozone and Methane. Environ. Sci. Technol. 2010, 2482−2489. (26) Eyring, V.; Stevenson, D. S.; Lauer, A.; Dentener, F. J.; Butler, T.; Collins, W. J.; Ellingsen, K.; Gauss, M.; Hauglustaine, D. A.; Isaksen, I. S. A.; Lawrence, M. G.; Richter, A.; Rodriguez, J. M.; Sanderson, M.; Strahan, S. E.; Sudo, K.; Szopa, S.; van Noije, T. P. C.; Wild, O. Multi-model simulations of the impact of international shipping on Atmospheric Chemistry and Climate in 2000 and 2030. Atmos. Chem. Phys. 2007, 7, 757−780. (27) Myhre, G.; Shindell, D.; Bréon, F.-M.; Collins, W.; Fuglestvedt, J.; Huang, J.; Koch, D.; Lamarque, J.-F.; Lee, D.; Mendoza, B.; Nakajima, T.; Robock, A.; Stephens, G.; Takemura, T.; Zhang, H., Anthropogenic and natural radiative forcing. In Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change; Stocker, T. F., Qin, D., Plattner, G.-K., Tignor, M., Allen, S. K., Doschung, J., Nauels, A., Xia, Y., Bex, V., Midgley, P. M., Eds.; Cambridge University Press: Cambridge, 2013; pp 659−740. (28) Stamnes, K.; Tsay, S.; Wiscombe, W.; Jayaweera, K. Numerically stable algorithm for discrete-ordinate-method radiative transfer in multiple scattering and emitting layered media. Appl. Opt. 1988, 27, 2502−2509. (29) Myhre, G.; Shine, K.; Radel, G.; Gauss, M.; Isaksen, I.; Tang, Q.; Prather, M.; Williams, J.; van Velthoven, P.; Dessens, O.; Koffi, B.; Szopa, S.; Hoor, R.; Grewe, V.; Borken-Kleefeld, J.; Berntsen, T.; Fuglestvedt, J. Radiative forcing due to changes in ozone and methane caused by the transport sector. Atmos. Environ. 2011, 45, 387−394. (30) Myhre, G.; Bellouin, N.; Berglen, T.; Berntsen, T.; Boucher, O.; Grini, A.; Isaksen, I.; Johnsrud, M.; Mishchenko, M.; Stordal, F.; Tanre, D. Comparison of the radiative properties and direct radiative effect of aerosols from a global aerosol model and remote sensing data over ocean. Tellus, Ser. B 2007, 59, 115−129.
M.S.E: Developed emission scenarios. T.F.B.: Developed emission scenarios. Notes
The authors declare no competing financial interest.
■
ACKNOWLEDGMENTS This work was funded by the Norwegian Research Council (Project No. 184873/S30, “Unlocking the Arctic Ocean: the climate impact of increased shipping and petroleum activities (ArcAct)”), by the EU project ACCESS (Arctic Climate Change Economy and Society), and the CRAICC (Cryosphere-Atmosphere Interactions in a Changing Arctic Climate) project. ACCESS received funding from the European Union under Grant Agreement No. 265863 within the Ocean of tomorrow call of the European Commission seventh framework programme. We thank Robbie Andrew for comments.
■
REFERENCES
(1) Stephenson, S.; Smith, L.; Agnew, J. Divergent long-term trajectories of human access to the Arctic. Nat. Clim. Change 2011, 1, 156−160. (2) Paxian, A.; Eyring, V.; Beer, W.; Sausen, R.; Wright, C. PresentDay and Future Global Bottom-Up Ship Emission Inventories Including Polar Routes. Environ. Sci. Technol. 2010, 1333−1339. (3) Peters, G.; Nilssen, T.; Lindholt, L.; Eide, M.; Glomsrod, S.; Eide, L.; Fuglestvedt, J. Future emissions from shipping and petroleum activities in the Arctic. Atmos. Chem. Phys. 2011, 11, 5305−5320. (4) Corbett, J.; Lack, D.; Winebrake, J.; Harder, S.; Silberman, J.; Gold, M. Arctic shipping emissions inventories and future scenarios. Atmos. Chem. Phys. 2010, 10, 9689−9704. (5) Arctic Council. Arctic Marine Shipping Assessment 2009 Report; Arctic Council, April 2009. (6) Serreze, M.; Holland, M.; Stroeve, J. Perspectives on the Arctic’s shrinking sea-ice cover. Science 2007, 1533−1536. (7) Smith, L.; Stephenson, S. New Trans-Arctic shipping routes navigable by midcentury. Proc. Natl. Acad. Sci. U.S.A. 2013, 110, E1191−E1195. (8) Eyring, V.; Isaksen, I. S. A.; Berntsen, T.; Collins, W. J.; Corbett, J. J.; Endresen, O.; Grainger, R. G.; Moldanova, J.; Schlager, H.; Stevenson, D. S. Transport impacts on atmosphere and climate: Shipping. Atmos. Environ. 2010, 44, 4735−4771. (9) Berntsen, T.; Fuglestvedt, J. Global temperature responses to current emissions from the transport sectors. Proc. Natl. Acad. Sci. U.S.A. 2008, 19154−19159. (10) Eide, M.; Dalsoren, S.; Endresen, O.; Samset, B.; Myhre, G.; Fuglestvedt, J.; Berntsen, T. Reducing CO2 from shipping - do nonCO2 effects matter? Atmos. Chem. Phys. 2013, 13, 4183−4201. (11) Berntsen, T.; Fuglestvedt, J.; Myhre, G.; Stordal, F.; Berglen, T. F. Abatement of greenhouse gases: Does location matter? Clim. Change 2006, 74, 377−411. (12) van Vuuren, D.; Edmonds, J.; Kainuma, M.; Riahi, K.; Weyant, J. A special issue on the RCPs. Clim. Change 2011, 109, 1−4. (13) Schultz, M.; van het Bolscher, M.; Pulles, T.; Brand, R.; Pereira, J.; Spessa, A.; Dalsøren, S.; van Nojie, T.; Szopa, S.; Schultz, M. Emission data sets and methodologies for estimating emissions. REanalysis of the TROpospheric chemical composition over the past 40 years. A long-term global modeling study of tropospheric chemistry funded under the 5th EU framework programme. EU-Contract No. EVK2-CT-2002-00170, 2008. (14) Dalsøren, S.; Eide, M.; Endresen, O.; Mjelde, A.; Gravir, G.; Isaksen, I. Update on emissions and environmental impacts from the international fleet of ships: the contribution from major ship types and ports. Atmos. Chem. Phys. 2009, 9, 2171−2194. (15) Ødemark, K.; Dalsøren, S. B.; Samset, B. H.; Berntsen, T. K.; Fuglestvedt, J. S.; Myhre, G. Short-lived climate forcers from current shipping and petroleum activities in the Arctic. Atmos. Chem. Phys. 2012, 12, 1979−1993. 13278
dx.doi.org/10.1021/es502379d | Environ. Sci. Technol. 2014, 48, 13273−13279
Environmental Science & Technology
Article
(31) Quaas, J.; Boucher, O. Constraining the first aerosol indirect radiative forcing in the LMDZ GCM using POLDER and MODIS satellite data. Geophys. Res. Lett. 2005, 32, L17814. (32) Quaas, J.; Boucher, O.; Lohmann, U. Constraining the total aerosol indirect effect in the LMDZ and ECHAM4 GCMs using MODIS satellite data. Atmos. Chem. Phys. 2006, 6, 947−955. (33) Hodnebrog, Ø.; Myhre, G.; Samset, B. H. How shorter black carbon lifetime alters its climate effect. Nat. Commun. 2014, 5. (34) Boucher, O.; Randall, D.; Artaxo, P.; Bretherton, C.; Feingold, G.; Forster, P.; Kerminen, V.-M.; Kondo, Y.; Liao, H.; Lohmann, U.; Rasch, P.; Satheesh, S. K.; Sherwood, S.; Stevens, B.; Zhang, X. Y., Clouds and aerosols. In Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change; Cambridge University Press: Cambridge, 2013; pp 571−657. (35) Berntsen, T. K.; Fuglestvedt, J. S.; Joshi, M. M.; Shine, K. P.; Stuber, N.; Ponater, M.; Sausen, R.; Hauglustaine, D. A.; Li, L. Response of climate to regional emissions of ozone precursors: sensitivities and warming potentials. Tellus, Ser. B 2005, 57, 283−304. (36) Joos, F.; Roth, R.; Fuglestvedt, J. S.; Peters, G. P.; Enting, I. G.; von Bloh, W.; Brovkin, V.; Burke, E. J.; Eby, M.; Edwards, N. R.; Friedrich, T.; Frölicher, T. L.; Halloran, P. R.; Holden, P. B.; Jones, C.; Kleinen, T.; Mackenzie, F. T.; Matsumoto, K.; Meinshausen, M.; Plattner, G. K.; Reisinger, A.; Segschneider, J.; Shaffer, G.; Steinacher, M.; Strassmann, K.; Tanaka, K.; Timmermann, A.; Weaver, A. J. Carbon dioxide and climate impulse response functions for the computation of greenhouse gas metrics: a multi-model analysis. Atmos. Chem. Phys. 2013, 13, 2793−2825. (37) Flato, G.; Marotzke, J.; Abiodun, B.; Braconnot, P.; Chou, S. C.; Collins, W.; Cox, P.; Driouech, F.; Emori, S.; Eyring, V.; Forest, C.; Gleckler, P.; Guilyardi, E.; Jakob, C.; Kattsov, V.; Reason, C.; Rummukainen, M., Evaluation of Climate Models. In Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change; Stocker, T. F., Qin, D., Plattner, G.-K., Tignor, M., Allen, S. K., Boschung, J., Nauels, A., Xia, Y., Bex, V., Midgley, P. M., Eds.; Cambridge University Press: Cambridge, 2013. (38) Ban-Weiss, G.; Cao, L.; Bala, G.; Caldeira, K. Dependence of climate forcing and response on the altitude of black carbon aerosols. Clim. Dynamics 2012, 38, 897−911. (39) Shindell, D.; Faluvegi, G. Climate response to regional radiative forcing during the twentieth century. Nat. Geosci. 2009, 2, 294−300. (40) Collins, W. J.; Fry, M. M.; Yu, H.; Fuglestvedt, J. S.; Shindell, D. T.; West, J. J. Global and regional temperature-change potentials for near-term climate forcers. Atmos. Chem. Phys. 2013, 13, 2471−2485. (41) Sand, M.; Berntsen, T.; Kay, J.; Lamarque, J.; Seland, O.; Kirkevag, A. The Arctic response to remote and local forcing of black carbon. Atmos. Chem. Phys. 2013, 13, 211−224. (42) Fuglestvedt, J.; Berntsen, T.; Eyring, V.; Isaksen, I.; Lee, D.; Sausen, R. Shipping emissions: From cooling to warming of climateand reducing impacts on health. Environ. Sci. Technol. 2009, 43, 9057− 9062.
13279
dx.doi.org/10.1021/es502379d | Environ. Sci. Technol. 2014, 48, 13273−13279
Climate Penalty for Shifting Shipping to the Arctic Jan S. Fuglestvedt,† Stig Bjørløw Dalsøren,*,† Bjørn Hallvard Samset,† Terje Berntsen,†,‡ Gunnar Myhre,† Øivind Hodnebrog,† Magnus Strandmyr Eide,§ and Trond Flisnes Bergh§ †
CICERO, Center for International Climate and Environmental Research-Oslo, Oslo, Norway University of Oslo, Department of Geosciences, Oslo, Norway § DNV GL, Høvik, Norway ‡
S Supporting Information *
ABSTRACT: The changing climate in the Arctic opens new shipping routes. A shift to shorter Arctic transit will, however, incur a climate penalty over the first one and a half centuries. We investigate the net climate effect of diverting a segment of Europe−Asia container traffic from the Suez to an Arctic transit route. We find an initial net warming for the first one-and-a-half centuries, which gradually declines and transitions to net cooling as the effects of CO2 reductions become dominant, resulting in climate mitigation only in the long term. Thus, the possibilities for shifting shipping to the Arctic confront policymakers with the question of how to weigh a century-scale warming with large uncertainties versus a long-term climate benefit from CO2 reductions.
■
INTRODUCTION The melting of Arctic sea ice may open new shipping routes between Europe and Asia.1−7 The Arctic route is shorter relative to the traditional Suez route and could result in significant fuel saving and reductions in CO2 emissions. In addition to CO2, ships emit a number of gases and aerosols with both warming and cooling effects operating on a broad range of time and spatial scales.8−10 The climate impacts of these components depend strongly on location and timing of emissions.11 In this study, detailed modeling of chemical, radiative, and temperature responses have been performed to quantify the net climate impact caused by new emissions in the Arctic and reduced emissions via the Suez route. We use Arctic shipping emission inventories3 for 2030 and 2050 with a gradual increase in container traffic on a new Arctic route between Europe (Rotterdam) and Asia (Yokohama). The Arctic transits occur in the period July−November when it is expected to be feasible and economically profitable to use the northern route.3 The advantage of the northern route compared to the traditional Suez route is shorter (43%) distance and travel time resulting in less fuel consumption (Figure S1, Supporting Information) and emissions for the same volume of transported cargo. This is, however, somewhat compensated by increased fuel consumption per kilometer to break through ice, especially in 2030. Applying the optimal Arctic route reduces the travel time by 37% in 2030 and 43% in 2050, while the fuel consumption is reduced by 29% and 37%. The total whole-year fuel consumption from shipping between Rotterdam and Yokohama is reduced by 10% in 2030 and 16% in 2050. Similar factors apply for relative reductions in emissions to air of chemical constituents (CO2, NOX (nitrogen © 2014 American Chemical Society
oxides), SOX (sulfur oxides), NMVOCs (non-methane volatile organic compounds), CO, black carbon (BC), and organic aerosols (OA)) as we assume identical emission factors for the components along the two routes.3 The rationale is that current ratified emission regulations will apply globally as intended. We do not assume differences that would appear if parts of the routes become situated in emission control areas (ECAs). A traffic shift from the Suez to the Arctic could then lead to smaller or larger reductions of NOX and SOX emissions dependent on which route is subjected to ECA regulations. The scenario from Peters et al.3 estimates a transported Rotterdam−Yokohama (R−Y) container volume of 1.4 MTEU (million twenty-foot equivalent unit) and 480 trips during 100 days of Arctic transit in 2030. This is 36% of the total volume for the R−Y route and 8% of the estimated container traffic between Europe and Asia. In 2050, the volumes transported during the 120 days of Arctic transit season rise to 2.5 MTEU corresponding to 850 journeys. This is 45% of the potential for the R−Y route and 10% of the container traffic between Europe and Asia. Due to the shorter sailing distance the cargo volume transported per day is higher in the Arctic. Therefore, moving this transport to the Arctic also induces emission decreases in the Suez route outside the Arctic transit season (Figure S2, Supporting Information). Received: Revised: Accepted: Published: 13273
May 14, October October October
2014 25, 2014 27, 2014 27, 2014
dx.doi.org/10.1021/es502379d | Environ. Sci. Technol. 2014, 48, 13273−13279
Environmental Science & Technology
■
Article
METHODS AND MODELS As a baseline emission scenario in the model simulations we use the RCP8.5 scenario12 for 2030 and 2050 nonship anthropogenic emissions and the RETRO inventory13 for year 2000 for natural emissions. In the Arctic, we replace the petroleum emissions in RCP8.5 with the emission inventory for 2030 and 2050 from Peters et al.3 We also include shipping related to this activity (both transport of products and supply of offshore installations) from Peters et al.3 Other shipping emissions for 2030 and 2050 are included at the same level as the 2004 inventory from Dalsøren et al.14 However, we take into account changes in emission factors of SOX, OA (correlated with SOX), and NOX due to existing IMO regulations. In the Arctic scenario, 36% (2030) and 45% (2050) of the R−Y container trade volume diverts from the traditional Suez route in the baseline inventory to a new Arctic transit route. The basic principles for the diversion are described in the introduction, and further details are given in Peters et al.3 The model simulations discussed in the Results and Discussion used the baseline scenario and the Arctic scenario for 2030 and 2050, respectively. Extra simulations performed to obtain additional insights are discussed in the Supporting Information. The different atmospheric conditions and sensitivity to emissions at high and low latitudes11,15 will determine the resulting climate impacts of near-term climate forcers (NTCF). In contrast, the impacts of CO2 and other long-lived greenhouse gases do not depend on emission location. Using a chemical transport model (CTM) and an offline radiative transfer model (RTM) we have calculated radiative forcing (RF) from shifting R−Y transport from Suez to the Arctic as described above. In addition to CO2, we include effects of NOX, CO, and NMVOCs on tropospheric ozone and methane as well as sulfate, nitrate, OA, and BC (in air, semidirect, and deposited on snow/ice) aerosols. The OsloCTM2 model was used to calculate the tropospheric distributions of 85 chemical species, among them hydrogen-, oxygen-, nitrogen-, and carbon-containing gases and also sulfate-, nitrate-, primary organic-, secondary organic-, black carbon- (BC), and sea-salt aerosols. Simulations were performed in T42 resolution (2.8° × 2.8°) with 60 vertical layers. Meteorological data for 2006 from the Integrated Forecast System (IFS) model (from ECMWF) were used in all simulations. The results do not account for the effect of future climate change on meteorology. However, the impacts of future sea ice conditions on surface dry deposition were included as we used the same gridded ice data as those used in the calculations of future Arctic ship emissions.3 The gas and aerosol schemes are described in refs 15−21. The model was used in previous studies on impacts of Arctic shipping.15,22 Modeled distributions of ozone and ozone precursors in coastal regions were evaluated and compared to observations and other models in former ship impact studies.23−26 The atmospheric distributions of ozone and aerosols in 2030 and 2050 were fed into a radiative-transfer model17 to calculate RF.27 The model is based on the DISORT radiative-transfer scheme28 and uses eight multiple-scattering streams and four shortwave spectral bands for aerosol simulations. For O3 RF calculations the same radiative transfer is applied but with a spectral resolution of 5 nm, and a broadband thermal infrared scheme is adopted29 with stratospheric temperature adjustment included. Temporal and spatial resolutions were the same as for OsloCTM2 for aerosols, whereas monthly mean data were used
for ozone. The optical properties of aerosols in the model are discussed in ref 30. Radiative forcings of direct and indirect aerosol effects were calculated as the difference in top-ofatmosphere energy flux between a simulation with all components at 2030 or 2050 levels and one that has one component changed to 2004 levels. To further study the differences in RF between, e.g., two 2030 conditions (for example, Suez and Arctic shipping), we take the difference between RFs for each component calculated using the above method. The radiative-transfer scheme was further used for calculating the effects of BC deposition on snow/ice albedo.19 The first indirect aerosol (cloud albedo) effect was calculated by estimating cloud droplet number from an empirical relationship with aerosol concentration31,32 and calculating the difference between aerosols at 2030 and 2004 levels as for the direct aerosol effect. See Ødemark et al.15 for details. The RF calculations use the same meteorological and ice data as the CTM. The semidirect aerosol effect for BC has been calculated using the National Center for Atmospheric Research (NCAR) Community Earth System Model (CESM1.0.4) (see the Supporting Information and Hodnebrog et al.33) with prescribed monthly mean BC concentrations from OsloCTM2. Aerosol-cloud interactions beyond the cloud albedo effect are not considered in this study. In general, this effect would enhance the cloud albedo effect; however, there is limited observational evidence indicating that its impact is of significant magnitude.34 We used the approach described in Berntsen et al.35 and Myhre et al.29 to calculate the RF from methane and associated ozone and stratospheric water vapor changes. We adapted the calculation of ozone changes from recent findings27 suggesting that the ozone RF equals half of the methane RF. The RF values from this method apply for the time when the perturbations have reached equilibrium conditions. For the development of CO2 levels and RF we have used the impulse response function from36 and radiative efficiency from AR5.27 We use the estimates of RF as input to a simple 2-box analytical climate model based on the approach of Berntsen and Fuglestvedt9 to calculate global mean temperature change by component over time. The climate model has a coupled atmosphere-mixed ocean layer box and a deep ocean box, allowing also for the long-term climate response; see Berntsen and Fuglestvedt9 for details. The RF is implemented as pulses decaying corresponding to the atmospheric residence time of each component. The model assumes an equilibrium climate sensitivity of 0.9 K/W/m2. The value is well within the range of IPCC AR537 estimates for radiative forcing and temperature change from a doubling of atmospheric CO2 concentration.
■
RESULTS AND DISCUSSION Figure 1 shows the calculated global annual RF, by component, and total non-CO2 and CO2 RF for 2030 and 2050. Shifting parts of the shipping from Suez to the Arctic route, i.e., reducing emissions at lower latitudes and introducing new emissions in the Arctic, gives positive net RFs from changes in non-CO2 components of 0.25 [0.07, 0.46] and 0.35 [0.05, 0.68] mW/m2, for 2030 and 2050, respectively. The large positive RFs from sulfate and the indirect effect of aerosols result from a strong positive RF from decreasing emissions along the Suez route, in addition to a small positive RF from increasing Arctic emissions. Despite different signs of the emission changes in the two regions the RF from both perturbations are positive. For the Suez route, high insolation 13274
dx.doi.org/10.1021/es502379d | Environ. Sci. Technol. 2014, 48, 13273−13279
Environmental Science & Technology
Article
for difference in sign of semidirect RF between these regions. However, the estimated uncertainty for the semidirect effect is larger than for any of the other RF mechanisms investigated here. The regional shift of emissions of NOX, CO, and NMVOCs leads to significant changes in ozone and methane. When the emissions decrease along the Suez route less ozone precursors are transported to high altitudes by vigorous convection during summer when the Intertropical Convergence Zone in the Indian Ocean moves north of the equator close to the route. At these altitudes and latitudes with efficient ozone production and long ozone lifetime this results in rather large reductions of ozone. Since the changes occur in the subtropics/tropics (Figure 2e) at high altitudes the impact of ozone changes on RF is relatively large. The impact of Arctic shipping on ozone is much smaller due to lower surface temperature and lower temperature gradient which influences the longwave forcing, as well as less sunlight which influences the shortwave forcing. The overall effect of a strong Suez signal and a weak Arctic signal is a strong net negative ozone RF (Figure 1). The RF due to methane and changes in associated components is weaker and of opposite sign to that from ozone. Decreased NOX emissions along the Suez route efficiently reduce OH, leading to enhanced methane RF. The changes in organic aerosols (OA) and nitrate are small and only give minor contributions to the total RF. Except for methane and methane-induced O3 and stratospheric H2O changes, the RF values calculated for the NTCFs reflect instantaneous changes (i.e., occurring on a time scale of days to months). CO2, however, has a response time of centuries,36 which means that the atmospheric levels are determined by emission history. Thus, assumptions about emission pathway are needed to quantify its total climate impact. For the R−Y Arctic transit route we have assumed linear trends from zero emissions in 2025 up to 2030 levels and further to 2050. The RF from CO2 is −0.009 [−0.008, −0.012] W/m2 in 2030 and −0.045 [−0.036, −0.057] W/m2 in 2050. This is small compared to the NTCF, but this gas has larger effects on longer time scales (see below). Direct emissions of CH4 and N2O are small and the RFs are found to be negligible. For the assumed linearized emission scenario described above, and with constant emissions after 2050, we calculated the response in global-mean temperature (Figure 3) over two centuries to capture the various time scales of the different components. Shifting shipping from Suez to Arctic initiates responses of very different magnitudes and signs. A group of small warming effects (nitrate, OA and stratospheric H2O) can be seen in Figure 3. BC on snow/ice (accounting for a high climate sensitivity to RF34) has a maximum warming effect around 2040 and declines thereafter due to reduced ice cover. After this time, the warming from methane, primary mode O3, sulfate, semidirect effect of BC and indirect aerosol effect dominates. Strong cooling effects from changes in direct aerosol effect of BC and O3 are found. In a separate category, we find the negative CO2 response which steadily grows larger. The net effect of all these contributions is a warming for the first oneand-a-half centuries, which thereafter switches to cooling due to the long response time and dominant effect of CO2. As shown in the inset, accounting for uncertainties (5−95%), based on uncertainties in RF from NTCF (Figure 1), in CO2 response36 and climate sensitivity (see the Supporting Information), shows that the warming period may last up to several centuries but
Figure 1. Effects in terms of global annual RF by component of shifting shipping routes from the Suez to the Arctic route (upper) and uncertainty distributions (lower) for 2030 and 2050. Uncertainty bars are given for 5−95% ranges. OA = organic aerosols, s.l. = short-lived, p.m. = primary mode.
and efficient reflection by sulfate and clouds explain the strong RF in vicinity of the Suez route (Figure 2a,c). In the Arctic there is, as expected, a negative RF over the oceans (in the vicinity of the route) due to enhancement of sulfate in the marine boundary layer (MBL). However, a more than compensating positive RF appears over northern America and Asia (Figure 2a,c). This occurs due to enhanced MBL oxidation of SO2 from nonship sources and efficient removal of resulting sulfate in the MBL, implying less sulfate transported to the free troposphere (see the Supporting Information). While the sign of the net RFs from sulfate and the indirect effect of aerosols are found to be positive and relatively large (Figure 1) we also estimate a large uncertainty range. When shipping via Suez is reduced and introduced in the Arctic we find a reduction in the net direct aerosol effect of black carbon (BC) (Figure 1). The main reason is that BC emitted into the Arctic atmosphere reaches lower altitudes and has shorter lifetime. On the other hand, BC emitted from Arctic shipping has a much larger effect when deposited on snow/ice (Figure 2b,d and Figure S5, Supporting Information); thus the shift to the Arctic causes a net positive global RF from BC on snow/ice. Due to the gradual reduction in Arctic sea ice, the RF from BC on snow/ice is smaller in 2050 than 2030. Both the RFs for direct aerosol effect of BC and BC on snow/ice have quite large uncertainties (Figure 1). For BC the main changes occur in the vicinity of the ship routes (Figure 2b), especially in the Arctic where mixing between the MBL and the free troposphere is rather inefficient. The semidirect effect of BC is negative from the Suez route and positive from the Arctic route. From moving shipping north, we find a positive net RF due to the semidirect effect, dominated by a reduction in negative forcing from the Suez region. The semidirect effect is strongly dependent on altitude,38 and differences in altitude of the BC perturbations from the Suez and Arctic routes are a main cause 13275
dx.doi.org/10.1021/es502379d | Environ. Sci. Technol. 2014, 48, 13273−13279
Environmental Science & Technology
Article
Figure 2. Effects in terms of annual RF of shifting shipping from the Suez to the Arctic route (in 2050) for sulfate (a), BC (direct effect) (b), indirect effects of aerosols on clouds (c), BC deposited on snow/ice, (d) and short-lived ozone (e). Note that the units on the color scales are different.
from the shorter route. To illustrate the long-term effect we simply assumed constant emissions after 2050. With a further retreat of sea ice after 2050 the difference in emissions compared to the Suez route would probably grow but not necessarily proportionally to the number of Arctic transits since fuel consumption and emissions depend on season and ice conditions. The chemical and physical responses in the atmosphere are dependent on season and strength of emission perturbation. When these parameters change a nonlinear response cannot be ruled out but it is likely that the effect of growing traffic along the route would be an augmentation of our obtained climate signal (sign of temperature change and evolution over time). With less ice Arctic transits from Western Europe to eastern Asia could start between a set of different destinations and via several Arctic travel routes. Changes in emissions compared to
also that the possibility of a net cooling effect from the start cannot be ruled out. We focused on global mean RF and temperature in this study. Recent studies show how regionally different RF patterns cause different regional patterns of temperature response,35,39−41 and further studies are needed to assess impacts of shifting shipping routes. Sulfate and black carbon with both a direct, semidirect, and strong snow/ice albedo effect are key components in the assessment of shifting shipping routes to the Arctic. In this study, we focus on only one shipping route where the conditions likely are profitable for Arctic transit shipping already in the near future (around year 2030). The climate signal is therefore small. However, our results show how inclusion of the full set of emissions is crucial as it make a significant modification to the effect of a CO2-only reduction 13276
dx.doi.org/10.1021/es502379d | Environ. Sci. Technol. 2014, 48, 13273−13279
Environmental Science & Technology
Article
Figure 3. Development in global mean temperature change by component and as total net effect including uncertainties. OA = organic aerosols, s.l. = short-lived, p.m. = primary mode. The inset figure shows the total net effect (black line) and uncertainties (5−95% confidence range as black dotted lines).
costs and higher CO 2 emissions with its long-term consequences and the cooling from NTCF versus the Arctic route with a century-scale warming but large inherent uncertainties due to NTCF.
the Suez route would then depend on sailing distance (destinations and route choice in the Arctic), season, and ice conditions. As long as we consider substitution of Suez transport with Arctic transits it is reasonable to assume approximately linearity in responses and use our results for the single Arctic route as an analogue. For substitution of other intercontinental routes (e.g., Panama, Southern Africa, Southern America), additional studies are needed since different physical conditions result in changed sensitivity of the climate response to emission perturbations. Emissions from shipping induce a series of climate effects, with RF of both signs. Here we have shown that reducing emissions at low latitudes and introducing emissions at higher latitudes adds complexity to assessments of climate impacts of future shipping routes. Thus, also in this case, the effects of NTCF need to be accounted for in addition to CO2. If the transient warming due to a movement is seen as unwanted, thenimplicitlythe negative RF by NTCF from shipping caused by the current R−Y Suez transits is valued as beneficial and, thus, as a form of “passive geo-engineering”. It is not obvious how negative RF should be considered in climate strategies.42 A question that needs to be addressed by policymakers is how to weigh the Suez route with higher fuel
■
ASSOCIATED CONTENT
S Supporting Information *
Additional information on applied methods. Uncertainty calculations. Results from additional model runs. Figures S1− S5. This material is available free of charge via the Internet at http://pubs.acs.org.
■
AUTHOR INFORMATION
Corresponding Author
*E-mail: [email protected]. Tel: +4745472629. Author Contributions
J.S.F.: Developed idea and project leader, analysis, article outline, and writing. S.B.D.: CTM calculations, RF calculations, analysis, article outline and writing. B.H.S.: RF calculations, analysis and writing. T.B.: Developed idea and project, analysis, temperature response, and uncertainty calculations and writing. G.M.: Developed idea and project, RF calculations, analysis, and writing. Ø.H.: Calculations of semidirect effect of BC. 13277
dx.doi.org/10.1021/es502379d | Environ. Sci. Technol. 2014, 48, 13273−13279
Environmental Science & Technology
Article
(16) Myhre, G.; Grini, A.; Metzger, S. Modelling of nitrate and ammonium-containing aerosols in presence of sea salt. Atmos. Chem. Phys. 2006, 6, 4809−4821. (17) Myhre, G.; Berglen, T.; Johnsrud, M.; Hoyle, C.; Berntsen, T.; Christopher, S.; Fahey, D.; Isaksen, I.; Jones, T.; Kahn, R.; Loeb, N.; Quinn, P.; Remer, L.; Schwarz, J.; Yttri, K. Modelled radiative forcing of the direct aerosol effect with multi-observation evaluation. Atmos. Chem. Phys. 2009, 9, 1365−1392. (18) Skeie, R.; Berntsen, T.; Myhre, G.; Tanaka, K.; Kvalevag, M.; Hoyle, C. Anthropogenic radiative forcing time series from preindustrial times until 2010. Atmos. Chem. Phys. 2011, 11, 11827− 11857. (19) Skeie, R.; Berntsen, T.; Myhre, G.; Pedersen, C.; Strom, J.; Gerland, S.; Ogren, J. Black carbon in the atmosphere and snow, from pre-industrial times until present. Atmos. Chem. Phys. 2011, 11, 6809− 6836. (20) Berglen, T.; Berntsen, T.; Isaksen, I.; Sundet, J. A global model of the coupled sulfur/oxidant chemistry in the troposphere: The sulfur cycle. J. Geophys. Res.: Atmos. 2004, 109, 27. (21) Hoyle, C.; Berntsen, T.; Myhre, G.; Isaksen, I. Secondary organic aerosol in the global aerosol - chemical transport model Oslo CTM2. Atmos. Chem. Phys. 2007, 7, 5675−5694. (22) Dalsoren, S.; Samset, B.; Myhre, G.; Corbett, J.; Minjares, R.; Lack, D.; Fuglestvedt, J. Environmental impacts of shipping in 2030 with a particular focus on the Arctic region. Atmos. Chem. Phys. 2013, 13, 1941−1955. (23) Endresen, O.; Sorgard, E.; Sundet, J.; Dalsoren, S.; Isaksen, I.; Berglen, T.; Gravir, G. Emission from international sea transportation and environmental impact. J. Geophys. Res.: Atmos. 2003, 108, 22. (24) Dalsoren, S.; Endresen, O.; Isaksen, I.; Gravir, G.; Sorgard, E., Environmental impacts of the expected increase in sea transportation, with a particular focus on oil and gas scenarios for Norway and northwest Russia. J. Geophys. Res.: Atmos. 2007, 112. (25) Dalsoren, S.; Eide, M.; Myhre, G.; Endresen, O.; Isaksen, I.; Fuglestvedt, J. Impacts of the Large Increase in International Ship Traffic 2000−2007 on Tropospheric Ozone and Methane. Environ. Sci. Technol. 2010, 2482−2489. (26) Eyring, V.; Stevenson, D. S.; Lauer, A.; Dentener, F. J.; Butler, T.; Collins, W. J.; Ellingsen, K.; Gauss, M.; Hauglustaine, D. A.; Isaksen, I. S. A.; Lawrence, M. G.; Richter, A.; Rodriguez, J. M.; Sanderson, M.; Strahan, S. E.; Sudo, K.; Szopa, S.; van Noije, T. P. C.; Wild, O. Multi-model simulations of the impact of international shipping on Atmospheric Chemistry and Climate in 2000 and 2030. Atmos. Chem. Phys. 2007, 7, 757−780. (27) Myhre, G.; Shindell, D.; Bréon, F.-M.; Collins, W.; Fuglestvedt, J.; Huang, J.; Koch, D.; Lamarque, J.-F.; Lee, D.; Mendoza, B.; Nakajima, T.; Robock, A.; Stephens, G.; Takemura, T.; Zhang, H., Anthropogenic and natural radiative forcing. In Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change; Stocker, T. F., Qin, D., Plattner, G.-K., Tignor, M., Allen, S. K., Doschung, J., Nauels, A., Xia, Y., Bex, V., Midgley, P. M., Eds.; Cambridge University Press: Cambridge, 2013; pp 659−740. (28) Stamnes, K.; Tsay, S.; Wiscombe, W.; Jayaweera, K. Numerically stable algorithm for discrete-ordinate-method radiative transfer in multiple scattering and emitting layered media. Appl. Opt. 1988, 27, 2502−2509. (29) Myhre, G.; Shine, K.; Radel, G.; Gauss, M.; Isaksen, I.; Tang, Q.; Prather, M.; Williams, J.; van Velthoven, P.; Dessens, O.; Koffi, B.; Szopa, S.; Hoor, R.; Grewe, V.; Borken-Kleefeld, J.; Berntsen, T.; Fuglestvedt, J. Radiative forcing due to changes in ozone and methane caused by the transport sector. Atmos. Environ. 2011, 45, 387−394. (30) Myhre, G.; Bellouin, N.; Berglen, T.; Berntsen, T.; Boucher, O.; Grini, A.; Isaksen, I.; Johnsrud, M.; Mishchenko, M.; Stordal, F.; Tanre, D. Comparison of the radiative properties and direct radiative effect of aerosols from a global aerosol model and remote sensing data over ocean. Tellus, Ser. B 2007, 59, 115−129.
M.S.E: Developed emission scenarios. T.F.B.: Developed emission scenarios. Notes
The authors declare no competing financial interest.
■
ACKNOWLEDGMENTS This work was funded by the Norwegian Research Council (Project No. 184873/S30, “Unlocking the Arctic Ocean: the climate impact of increased shipping and petroleum activities (ArcAct)”), by the EU project ACCESS (Arctic Climate Change Economy and Society), and the CRAICC (Cryosphere-Atmosphere Interactions in a Changing Arctic Climate) project. ACCESS received funding from the European Union under Grant Agreement No. 265863 within the Ocean of tomorrow call of the European Commission seventh framework programme. We thank Robbie Andrew for comments.
■
REFERENCES
(1) Stephenson, S.; Smith, L.; Agnew, J. Divergent long-term trajectories of human access to the Arctic. Nat. Clim. Change 2011, 1, 156−160. (2) Paxian, A.; Eyring, V.; Beer, W.; Sausen, R.; Wright, C. PresentDay and Future Global Bottom-Up Ship Emission Inventories Including Polar Routes. Environ. Sci. Technol. 2010, 1333−1339. (3) Peters, G.; Nilssen, T.; Lindholt, L.; Eide, M.; Glomsrod, S.; Eide, L.; Fuglestvedt, J. Future emissions from shipping and petroleum activities in the Arctic. Atmos. Chem. Phys. 2011, 11, 5305−5320. (4) Corbett, J.; Lack, D.; Winebrake, J.; Harder, S.; Silberman, J.; Gold, M. Arctic shipping emissions inventories and future scenarios. Atmos. Chem. Phys. 2010, 10, 9689−9704. (5) Arctic Council. Arctic Marine Shipping Assessment 2009 Report; Arctic Council, April 2009. (6) Serreze, M.; Holland, M.; Stroeve, J. Perspectives on the Arctic’s shrinking sea-ice cover. Science 2007, 1533−1536. (7) Smith, L.; Stephenson, S. New Trans-Arctic shipping routes navigable by midcentury. Proc. Natl. Acad. Sci. U.S.A. 2013, 110, E1191−E1195. (8) Eyring, V.; Isaksen, I. S. A.; Berntsen, T.; Collins, W. J.; Corbett, J. J.; Endresen, O.; Grainger, R. G.; Moldanova, J.; Schlager, H.; Stevenson, D. S. Transport impacts on atmosphere and climate: Shipping. Atmos. Environ. 2010, 44, 4735−4771. (9) Berntsen, T.; Fuglestvedt, J. Global temperature responses to current emissions from the transport sectors. Proc. Natl. Acad. Sci. U.S.A. 2008, 19154−19159. (10) Eide, M.; Dalsoren, S.; Endresen, O.; Samset, B.; Myhre, G.; Fuglestvedt, J.; Berntsen, T. Reducing CO2 from shipping - do nonCO2 effects matter? Atmos. Chem. Phys. 2013, 13, 4183−4201. (11) Berntsen, T.; Fuglestvedt, J.; Myhre, G.; Stordal, F.; Berglen, T. F. Abatement of greenhouse gases: Does location matter? Clim. Change 2006, 74, 377−411. (12) van Vuuren, D.; Edmonds, J.; Kainuma, M.; Riahi, K.; Weyant, J. A special issue on the RCPs. Clim. Change 2011, 109, 1−4. (13) Schultz, M.; van het Bolscher, M.; Pulles, T.; Brand, R.; Pereira, J.; Spessa, A.; Dalsøren, S.; van Nojie, T.; Szopa, S.; Schultz, M. Emission data sets and methodologies for estimating emissions. REanalysis of the TROpospheric chemical composition over the past 40 years. A long-term global modeling study of tropospheric chemistry funded under the 5th EU framework programme. EU-Contract No. EVK2-CT-2002-00170, 2008. (14) Dalsøren, S.; Eide, M.; Endresen, O.; Mjelde, A.; Gravir, G.; Isaksen, I. Update on emissions and environmental impacts from the international fleet of ships: the contribution from major ship types and ports. Atmos. Chem. Phys. 2009, 9, 2171−2194. (15) Ødemark, K.; Dalsøren, S. B.; Samset, B. H.; Berntsen, T. K.; Fuglestvedt, J. S.; Myhre, G. Short-lived climate forcers from current shipping and petroleum activities in the Arctic. Atmos. Chem. Phys. 2012, 12, 1979−1993. 13278
dx.doi.org/10.1021/es502379d | Environ. Sci. Technol. 2014, 48, 13273−13279
Environmental Science & Technology
Article
(31) Quaas, J.; Boucher, O. Constraining the first aerosol indirect radiative forcing in the LMDZ GCM using POLDER and MODIS satellite data. Geophys. Res. Lett. 2005, 32, L17814. (32) Quaas, J.; Boucher, O.; Lohmann, U. Constraining the total aerosol indirect effect in the LMDZ and ECHAM4 GCMs using MODIS satellite data. Atmos. Chem. Phys. 2006, 6, 947−955. (33) Hodnebrog, Ø.; Myhre, G.; Samset, B. H. How shorter black carbon lifetime alters its climate effect. Nat. Commun. 2014, 5. (34) Boucher, O.; Randall, D.; Artaxo, P.; Bretherton, C.; Feingold, G.; Forster, P.; Kerminen, V.-M.; Kondo, Y.; Liao, H.; Lohmann, U.; Rasch, P.; Satheesh, S. K.; Sherwood, S.; Stevens, B.; Zhang, X. Y., Clouds and aerosols. In Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change; Cambridge University Press: Cambridge, 2013; pp 571−657. (35) Berntsen, T. K.; Fuglestvedt, J. S.; Joshi, M. M.; Shine, K. P.; Stuber, N.; Ponater, M.; Sausen, R.; Hauglustaine, D. A.; Li, L. Response of climate to regional emissions of ozone precursors: sensitivities and warming potentials. Tellus, Ser. B 2005, 57, 283−304. (36) Joos, F.; Roth, R.; Fuglestvedt, J. S.; Peters, G. P.; Enting, I. G.; von Bloh, W.; Brovkin, V.; Burke, E. J.; Eby, M.; Edwards, N. R.; Friedrich, T.; Frölicher, T. L.; Halloran, P. R.; Holden, P. B.; Jones, C.; Kleinen, T.; Mackenzie, F. T.; Matsumoto, K.; Meinshausen, M.; Plattner, G. K.; Reisinger, A.; Segschneider, J.; Shaffer, G.; Steinacher, M.; Strassmann, K.; Tanaka, K.; Timmermann, A.; Weaver, A. J. Carbon dioxide and climate impulse response functions for the computation of greenhouse gas metrics: a multi-model analysis. Atmos. Chem. Phys. 2013, 13, 2793−2825. (37) Flato, G.; Marotzke, J.; Abiodun, B.; Braconnot, P.; Chou, S. C.; Collins, W.; Cox, P.; Driouech, F.; Emori, S.; Eyring, V.; Forest, C.; Gleckler, P.; Guilyardi, E.; Jakob, C.; Kattsov, V.; Reason, C.; Rummukainen, M., Evaluation of Climate Models. In Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change; Stocker, T. F., Qin, D., Plattner, G.-K., Tignor, M., Allen, S. K., Boschung, J., Nauels, A., Xia, Y., Bex, V., Midgley, P. M., Eds.; Cambridge University Press: Cambridge, 2013. (38) Ban-Weiss, G.; Cao, L.; Bala, G.; Caldeira, K. Dependence of climate forcing and response on the altitude of black carbon aerosols. Clim. Dynamics 2012, 38, 897−911. (39) Shindell, D.; Faluvegi, G. Climate response to regional radiative forcing during the twentieth century. Nat. Geosci. 2009, 2, 294−300. (40) Collins, W. J.; Fry, M. M.; Yu, H.; Fuglestvedt, J. S.; Shindell, D. T.; West, J. J. Global and regional temperature-change potentials for near-term climate forcers. Atmos. Chem. Phys. 2013, 13, 2471−2485. (41) Sand, M.; Berntsen, T.; Kay, J.; Lamarque, J.; Seland, O.; Kirkevag, A. The Arctic response to remote and local forcing of black carbon. Atmos. Chem. Phys. 2013, 13, 211−224. (42) Fuglestvedt, J.; Berntsen, T.; Eyring, V.; Isaksen, I.; Lee, D.; Sausen, R. Shipping emissions: From cooling to warming of climateand reducing impacts on health. Environ. Sci. Technol. 2009, 43, 9057− 9062.
13279
dx.doi.org/10.1021/es502379d | Environ. Sci. Technol. 2014, 48, 13273−13279
