Passenger transport decarbonisation under different equity considerations

Climate change is often seen as an equity problem, as it is caused primarily by richer countries and households, while its impacts are generally expected to affect poorer countries and households significantly stronger. Climate policy aiming at mitigating these impacts, however, can also have a regressive impact on societies, unless it is designed such that the costs of mitigation are shared progressively depending on wealth differences. At the same time, historical energy transitions have often been driven by wealthy consumers demanding higher quality goods and services, which consequently grew from niche to mainstream technologies. Particularly the transportation sector is a sector difficult to decarbonise, while there are significant differences in contribution between poorer and wealthier users. This study uses a global integrated assessment model (GCAM) with 10 different income groups for each of the 32 regions to compare several decarbonisation scenarios for passenger transportation. On the one hand, implementing a general cap-and-trade policy for transport emissions, while traditionally seen as the economically optimal policy, affects poorer individuals significantly more in terms of access to transport services in a decarbonised world. On the other hand, implementing fixed caps for each country and income group, which cannot be traded with consumers at lower other income groups or countries, and are globally equal for each individual, leads to significantly higher costs for higher income individuals, but does not affect the access to transport services of poorer individuals as strongly. Also, this last alternative leads to a significantly faster take-up of modern clean technologies in transport.