Creutzig, Felix

Edelenbosch, Oreane Y.

Jochem, Patrick

Mattauch, Linus

McCollum, David

Minx, Jan

Vuuren, Detlef P. van

KITopen

By Felix Creutzig,1,2* Patrick Jochem,3Oreane Y. Edelenbosch,4 Linus Mattauch,1,2 Detlef P. van Vuuren,4,5David McCollum,6 Jan Minx1,7Global emissions scenarios studies, such as those informing the Inter-governmental Panel on Climate Change (IPCC) 5th Assessment Re-port (AR5), highlight the importance of the transport sector for climate change mitigation along with the difficul-ties of achieving deep reductions therein (1) [supplementary materials (SM)]. Trans-port is responsible for about 23% of total energy-related CO2 emissions worldwide (2). The sector is growing more rapidly than most oth-ers, with emissions projected to double by 2050. Global scenario studies, specifically those produced by integrated assessment models (IAMs), communicate aggregate mitigation potentials by sec-tors in IPCC reports. Yet recent evidence indicates that emissions may be reduced further than these global scenario studies suggest if policy-makers use the full suite of policies at their disposal.If current trends continue, the global number of light-duty vehicles will roughly double by midcentury, driven by rising af-fluence especially in China, India, and South East Asia (3). Demand for freight transport (road, rail, shipping, and air) and passen-ger aviation is projected to surge as well. In recent years, CO2 emissions from trans-port have stabilized in the European Union and the United States as fuel economy and emission standards were tightened. Muni-cipalities worldwide have implemented lo-cal measures to reduce emissions of urban transport systems. However, these efforts have not been able to slow sectoral emis-sion growth on the global level; there needs to be a broader suite of complementary, and enforced, policies in order to succeed.The IPCC AR5 indicates that stabilization of CO2 emissions in the transport sector by 2050 at roughly 2010 levels would be con-sistent with the 2°C global mean tempera-ture increase target [i.e., 430 to 480 parts per million (ppm) CO2-equivalent (CO2 -eq)]. But this transport mitigation burden is con-ditional on emission reductions in other sectors. The 2050 target for the transport sector is relatively modest because, in these global emissions scenarios, the power sector often compensates for residual emissions in the transport sector by removing CO2 from the atmosphere via bioenergy and carbon capture and storage (SM). If non-transport reductions turn out to be more difficult to achieve, then transport would need to halve its emissions by midcentury.CAN AMBITIOUS CO2 REDUCTIONS BE ACHIEVED? Transport mitigation options can, in principle, lower emissions by reduc-ing (i) overall transport demand growth (re-ducing distance traveled; shifting to more efficient modes), (ii) the amount of energy needed for propelling a vehicle over a given distance (increase fuel efficiency), or (iii) the carbon intensity of transport fuels [gCO2/MJ] (fuel shift). In global scenarios, options (ii) and (iii) form the main mitiga-tion options (1). In contrast, many urban transport experts highlight the potential of option (i), such as compact urban develop-ment, bus rapid transit, bicycle highways, and telecommuting. As the last-mentioned options often lead to nonclimate benefits at the local level, they are increasingly be-coming part of municipal agendas world-wide. But current-generation global IAMs lack necessary spatial and/or jurisdictional resolution to represent local, often idiosyn-cratic, solutions of this type. Whereas IAMs remain crucial for the big picture, trans-port-specific models with higher resolution in space and technological data comple-ment IAMs and show that more ambitious mitigation appears plausible.We illustrate the main challenges using results of three representative scenario runs by the IAM IMAGE (see the figure, A to C) (SM) (4) in order to then contextual-ize the relevance of additional mitigation options. In the most ambitious case, total emissions in the transport sector will be 4.2 Gt CO2 in 2050, within the range of the 430 to 480 ppm CO2 -eq scenarios. But which transport sector developments substanti-ate mitigation scenarios? We sketch key elements of the solution space, following the IPCC (1, 2) and, drawing on other litera-ture, point to two options in land passen-Transport: A roadblock toclimate change mitigation?Urban mobility solutions foster climate mitigation“...transport could... nearly halve its CO2 emissions by midcentury….”8060402000.0 0.5 1.0 1.5050100 1002050 ambitious mitigation: 450 ppm CO2-eq scenario 2050 moderate mitigation: 650 ppm CO2-eq scenario 2050 business as usual2011 referenceCO2 intensity (gCO2/MJ)Energy e2ciency (MJ/pkm)Demand(trillionpkm)Demand(trillionpkm)Demand(trilliontkm)A  Land transport passenger8060402000.0 0.5 1.0 1.5 2.0 2.5050CO2intensity(gCO2/MJ)Energy e2ciency (MJ/pkm)B  Aviation passenger8060402000.0 0.50100200CO2intensity(gCO2/MJ)Energy e2ciency (MJ/tkm)C  Total freightModeled transport CO2 emissions, in 2011 and in 2050, based on data from 2005. (See SM). (A) Land passenger (passenger-kilometer, pkm); (B) aviation; and (C) freight transport (metric ton–kilometer, tkm), as modeled by the IAM IMAGE (14) (See SM). Emissions, calculated as the product of the three axes (CO2 intensity, energy efficiency, and demand), can be visualized by the volume of the boxes.ger transport that complement the solution space: electric cars and urban transport de-mand management.The scenarios show that passenger road transport continues to be responsible for the highest emissions share within the transport sector (part A); but aviation dis-plays the highest growth in emissions (part B), consistent with historical trends of shifting to faster modes. Aviation requires considerable fuel per passenger-km trav-eled (part B), whereas maritime transport, a major component of freight demand, is highly fuel-efficient (part C).Road transport could contribute a major mitigation share by (i) continuing to ag-gressively increase efficiency; (ii) shifting from fossil fuels to electric-drive vehicles; and (iii) slowing demand growth, especially in urban settings. First, continuously im-proved technical standards in road trans-port in all major auto markets worldwide have resulted in efficiency gains for new light-duty vehicles of about 2 to 4% per year (5). Although this rate can be extrapolated for another decade, future efficiency gains are likely to become more costly without sacrificing vehicle size, safety, equipment, or comfort. But a shift in societal prefer-ences toward smaller cars would allow for reduced incremental costs.Second, deeply decarbonizing road transport would involve a large-scale shift from gasoline and diesel to biofuels, elec-tricity, and/or hydrogen, either in dedi-cated battery-electric or fuel-cell vehicles or in mixed configurations, such as plug-in hybrid-electric vehicles. Our scenario, similar to those assessed by AR5, indicates only partial decarbonization until 2050 (Fig. 1A), mostly because production of advanced vehicle technologies and low-carbon fuels with high-energy density are expected to remain costly for several de-cades (relative to gasoline and diesel used in efficient conventional vehicles). There is no agreement on which of the three al-ternative energy carriers will replace for fossil liquid fuels in the long term, but it appears likely that one or several of these will come to dominate in the second half of this century if deep cuts in emissions are to be achieved (6). Battery-electric mobil-ity, for instance, might take off faster than expected owing to substantial declines in battery prices (7), which would make battery-electric travel less expensive than conventional fossil fuel based mobility [(8) see also SM]. Hence, battery-electric cars are likely to reduce emissions further until 2050 [even though indirect emissions from electricity generation are not negli-gible (9)], on top of the emission reduction shown in IMAGE.Third, infrastructure development, land-use policies and behavioral interventions can catalyze further emission reductions; these, however, are hard to assess quanti-tatively in current-generation global IAMs that lack the fine-scale resolution of local infrastructure and behavioral issues (10). In general, those strategies are not mod-eled explicitly. Options include shifting to modes with low carbon intensities, park-ing management and congestion charges, smart growth policies, and behavioral mea-sures. Such options also carry potentially large social benefits, e.g., reduced noise, air pollution; traffic congestion; and risk of obesity-related diseases, depression, and dementia, which often create strong incen-tives for local action. In sum, the combined mitigation potential in urban transport via spatial planning, transport pricing, and behavioral options amounts to 20 to 50% between 2010 and 2050, compared with baseline (11) (fig. S1).Infrastructure investments and behav-ioral options can produce cost savings that are not typically included in global esti-mates of mitigation costs. Although low-carbon infrastructure options may include expensive up-front construction (e.g., high-speed rail tracks), such investments could lead to enormous savings from building and maintaining fewer roads and parking spaces over coming decades. One study puts these infrastructure investment cost savings for low-carbon transport at around $20 trillion by 2050 globally (12). Rededi-cating existing urban infrastructure to non-motorized transport (e.g., pedestrian zones and bicycle lanes) can be achieved at little cost. Behavioral interventions have mostly zero or low monetary costs (SM), but unlocking their considerable mitiga-tion potential requires policies that explic-itly take nonstandard preferences, beliefs, and decision-making processes into ac-count, as well as normative considerations of policy-makers (13).If both urban transport mitigation op-tions and increasingly cost-effective battery-electric cars are fully utilized, there are reasons to believe global transport could be on track to nearly halve its CO2 emissions by midcentury, which would bring the sector in line with the 2∞C target (SM). Higher fuel taxes would foster long-term development toward compact urban form and low-carbon urban transport (14) and, at the same time, incentivize faster market penetration of battery-electric vehicles (7). In fact, avoiding rebound effects associated with the sub-stantially greater efficiency of electric vehi-cles necessitates high prices on fossil fuels. So far, however, we see little global appetite among policy-makers for seriously discuss-ing thorny transport issues in public debates and international climate negotiations. Un-less this changes swiftly, transport may re-main a roadblock to the world’s efforts to mitigate climate change. REFERENCES AND NOTES 1. O. Edenhofer et al., in Climate Change 2014: Mitigation of Climate Change. Contribution of Working Group III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change, O. Edenhofer et al., Eds. (Cambridge Univ. Press, New York, 2014), pp. 33 108. 2. R. Sims et al., in Climate Change 2014: Mitigation of Climate Change. Contribution of Working Group III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change, O. Edenhofer et al., Eds. (Cambridge Univ. Press, New York, 2014), pp. 599 670.. 3. D. Sperling, D. Gordon, Two Billion Cars (Oxford Univ. Press, New York, 2009). 4. B. Girod, D. P. van Vuuren, S. Deetman, Energy Policy 45, 152 (2012). 5. S. L. Winkler, T. J. Wallington, H. Maas, H. Hass, Environ. Sci. Technol. 48, 6453 (2014). 6. R. Pietzcker et al., Energy 64, 95 (2014). 7. B. Nykvist, M. Nilsson, Nat. Clim. Change 5, 329 (2015). 8. National Research Council, Transitions to Alternative Fuels and Vehicles (National Academies Press, Washington, DC, 2013). 9. P. Jochem, S. Babrowski, W. Fichtner, Transp. Res. A: Policy Pract. 78, 68 (2015). 10. T. Schwanen, D. Banister, J. Anable, Transp. Res. A Policy Pract. 45, 993 (2011). 11. F. Creutzig, Transp. Rev. 10.1080/01441647.2015.1079277 (2015). 12. J. Dulac, “Global land transport infrastructure requirements” (International Energy Agency, Paris, 2013). 13. L. Mattauch, M. Ridgway, F. Creutzig, Transp. Res. Part D Transp. Environ. 10.1016/j.trd.2015.08.006 (2015). 14. F. Creutzig, Urban Clim. 10, 63 (2014).ACKNOWLEDGMENTSWe thank B. Girod and J. Römer for support in modeling and R. Pietzcker, W. Rothengatter, and Y. Hayashi for helpful discussions. We acknowledge funding by EU Framework Programme 7 (FP 7) 2007 2013 no. 308329 (ADVANCE).“Infrastructure investments and behavioral options can produce cost savings that are not typically included in global estimates of mitigation costs.”1Mercator Research Institute on Global Commons and Climate Change (MCC), 10829 Berlin, Germany. 2Technical University Berlin, 10623 Berlin, Germany. 3Karlsruhe Institute of Technology (KIT), 76131 Karlsruhe, Germany. 4PBL Netherlands Environmental Assessment Agency, 3720AH Bilthoven, Netherlands. 5Copernicus Institute of Sustainable Development of Geosciences, Utrecht University, 3584CS Utrecht, Netherlands. 6International Institute for Applied Systems Analysis (IIASA), 2361 Laxenburg, Austria. 7Hertie School of Governance, 10117 Berlin, Germany. *Corresponding author. E mail: creutzig@mcc berlin.net      Repository KITopen  Dies ist ein Postprint/begutachtetes Manuskript.  Empfohlene Zitierung:  Creutzig, F.; Jochem, P.; Edelenbosch, O. Y.; Mattauch, L.; Vuuren, D. P. van; McCollum, D.; Minx, J. Transport: A roadblock to climate change mitigation?. 2015. Science, 350.  doi:10.554/IR/1000055150    Zitierung der Originalveröffentlichung:  Creutzig, F.; Jochem, P.; Edelenbosch, O. Y.; Mattauch, L.; Vuuren, D. P. van; McCollum, D.; Minx, J. Transport: A roadblock to climate change mitigation?. 2015. Science, 350 (6263), 911-912.  doi:10.1126/science.aac8033                 Lizenzinformationen: KITopen-Lizenz 

Transport: A roadblock to climate change mitigation?

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Transport: A roadblock to climate change mitigation?

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