The IPCC Forth Assessment Report postulates that global warming can be limited to 2˚C by deploying technologies that are currently available or expected to be commercialized in the coming decades. However, neither specific technological pathways nor reduction targets for different sectors have been established. Using direct CO2 emissions from the growing passenger car stock in China as example, we investigate whether it is sufficient to focus on reductions within the different sectors of energy use while assuming even contribution of all sectors and a unitary global per capita emission quota. We performed a dynamic Material Flow Analysis on the passenger car stock to compute future direct CO2 emissions depending on population, car utilization, and fuel efficiency. Massive deployment of present prototypes of fuel efficient cars can reduce emissions by about 45% compared to average car use in industrialized countries; moderately lower use could contribute with another 33 %. Still, emissions remain about two times higher than the 2˚C target and hence, alternative fuels, more significant lifestyle changes, or reduction potentials beyond the sector boundary have to be explored. The proposed model facilitates the necessary extension as it offers direct interfaces to material industries, fuel production, and supply of scrap vehicles.
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