Modeling fuel- and vehicle- type specific CO2 emissions from global on-road vehicles during 1970-2020

Vehicles are one of the most important contributors to global anthropogenic CO₂ emissions. However, lack of fuel- and vehicle- type specific information about global on-road CO₂ emissions from existing datasets, which are only available at sector level, makes it insufficient to support establishment of emission mitigation strategies. Thus, a fleet model is developed in this study and CO₂ emissions from global on-road vehicles during 1970-2020 are estimated at vehicle level. Here we access the fuel- and vehicle- type specific characteristics of both vehicular CO₂ emissions and vehicle ownership, and highlight the trend in the intensity of CO₂ emissions and ownership of on-road vehicles in hotspot regions. We find that, heavy-duty trucks and buses which account for less than 10% of global vehicle ownership but represent over 30% of on-road CO₂ emissions. Contribution of diesel vehicles to global on-road CO₂ emissions has doubled during 1970-2020, driven by the shift in fuel-type distribution of vehicle ownership. As the top four vehicle markets, vehicles per thousand people in the United States, European Union, China and India all increased significantly from 1970 to 2020 while vehicle intensity China and India was still lower than global average level, which indicates that developing countries have to face great challenges in vehicular decarbonization in the future. CO₂ emissions per vehicle in these regions generally decreased for the last 50 years, but vehicular CO₂ emission intensity in the United States and European Union were relatively higher, meaning that there're still large potentials for developed countries in vehicular CO₂ emission mitigation. These findings provide better understanding of trends of historical CO₂ emissions from on-road vehicles, as well as insights into the effective governance of CO₂ emissions in the future.