Long-term transport energy demand and climate policy: Alternative visions on transport decarbonization in energy-economy models

Decarbonizing transport will be necessary to limit global warming below 2 °C. Due to persistent reliance on fossil fuels, it is posited that transport is more difficult to decarbonize than other sectors. To test this hypothesis, we compare long-term transport energy demand and emission projections for China, USA and the world from five large-scale energy-economy models. We diagnose the model's characteristics by subjecting them to three climate policies. We systematically analyze mitigation levers along the chain of causality from mobility to emissions, finding that some models lack relevant mitigation options. We partially confirm that transport is less reactive to a given carbon tax than the non-transport sectors: in the first half of the century, transport mitigation is delayed by 10-30 years compared to non-transport mitigation. At high carbon prices towards the end of the century, however, the three global models achieve deep transport emission reductions by >90% through the use of advanced vehicle technologies and low-carbon primary energy; especially biomass with CCS (carbon capture and sequestration) plays a crucial role. The extent to which earlier mitigation is possible strongly depends on implemented technologies and model structure. Compared to the global models, the two partial-equilibrium models are less flexible in their reaction to climate policies.