Sustainable Transportation Energy Pathways (STEPS)
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Suggested Citation: Sims, Ralph, Roberto Schaeffer, Felix Creutzig, Xochitl Cruz-Núñez, Marcio D’Agosto, Delia Dimitriu, Maria J. Figueroa Meza, Lewis Fulton, Shigeki Kobayashi, Oliver Lah, Alan McKinnon, Peter Newman, Minggao Ouyang, James J. Schauer, Daniel Sperling, Geetam Tiwari (2014) "Transport," chapter 8 in Edenhofer, O., R. Pichsâ€Madruga, Y. Sokona, E. Farahani, S. Kadner, K. Seyboth, A. Adler, I. Baum, S. Brunner, P. Eickemeier, B. Kriemann, J. Savolainen, S. Schlömer, C. von Stechow, T. Zwickel and J. C. Minx (eds.), Climate Change 2014: Mitigation of Climate Change (Working Group III Contribution to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change). Cambridge University Press.
Reducing global transport greenhouse gas (GHG) emissions will be challenging since the continuing growth in passenger and freight activity could outweigh all mitigation measures unless transport emissions can be strongly decoupled from GDP growth (high confidence).
The transport sector produced 6.7 GtCO2 (7.0 GtCO2eq including nonâ€CO2 gases) of direct GHG emissions in 2010 and hence was responsible for approximately 23% of total energyâ€related CO2 emissions [8.1]. Growth in GHG emissions has continued since the Fourth Assessment Report (AR4) in spite of more efficient vehicles (road, rail, water craft, and aircraft) and policies being adopted. (robust evidence; high agreement)[Section 8.1, 8.3].
Without aggressive and sustained mitigation policies being implemented, transport emissions could increase at a faster rate than emissions from the other energy endâ€use sector and reach around 12 Gt CO2eq/yr by 2050. Transport demand per capita in developing and emerging economies is far lower than in Organisation for Economic Coâ€operation and Development (OECD) countries but is expected to increase at a much faster rate in the next decades due to rising incomes and development of infrastructure. Analyses of both sectoral and integrated model scenarios suggest a higher emission reduction potential in the transport sector than the levels found possible in AR4 and at lower costs. Since many integrated models do not contain a detailed representation of infrastructural and behavioural changes, their results for transport can possibly be interpreted as conservative. If pricing and other stringent policy options are implemented in all regions, substantial decoupling of transport GHG emissions from gross domestic product (GDP) growth seems possible. A strong slowing of lightâ€duty vehicle (LDV) travel growth per capita has already been observed in several OECD cities suggesting possible saturation. (medium evidence, medium agreement) [8.6, 8.9, 8.10]