To meet the terms of the 2015 Paris Agreement, the global energy system must be entirely decarbonized by the end of this century. Two scenarios have been developed: a reference case (REF) and an advanced 100% renewable energy scenario (ADV). ADV reflects the trends in global energy systems and will decarbonize the entire energy system by 2050. Those results are compared with the IPCC AR5 450 ppm scenarios, in terms of the 2050 energy demand projections — primary and final energy — and the demands for the transport and building sectors because they are important in urban environments. The results are further discussed with regard to the impact on urban infrastructures and the role of megacities in the global energy consumption pattern. Under the assumption that urbanization rates will remain at the 2015 level until 2050, the annual energy demand for buildings in urban areas is expected to increase by 27 EJ under the reference scenario (REF), from 57 EJ to 84 EJ per year, whereas ADV would lead to an overall reduction to 46 EJ per year by 2050, while the population and GDP continue to grow. Overall, the global energy demand in the transport sector is expected to increase by over 60% by 2050 under REF, whereas the deep mitigation pathway (ADV) reduces the transport energy demand below that of the base year, to 70 EJ per year. This is a significant reduction, even compared with other 450 ppm scenarios, and can be achieved by a drastic shift to electric mobility in response to vehicle efficiency standards, a phasing-out of combustion engines in the transport sector by 2030, and a modal shift in favor of urban public transport. The global energy demand for the building sector in ADV shows a smaller deviation in comparison to other 450 ppm scenarios than that for the transport sector.
• Comparison of deep-decarbonization scenarios reveals large differences in final energy demand projections.
• The projected electricity demand for 2050 varies significantly, between 65 000 TWh/yr and 25 000 TWh/yr.
• The presented low-carbon ADV scenario combines 100% renewable energy for all sectors with high efficiency.
• 100% renewable energy scenarios use high electrification rates for transport and the heating sector.
• Estimated CO2 reduction potential for urban buildings accounts for 35 Gt CO2 by 2050.