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

Abstract. Vehicles are among the most important contributors to global anthropogenic CO₂ emissions. However, the lack of fuel-, vehicle type-, and age-specific information about global on-road CO₂ emissions in existing datasets, which are available only at the sector level, makes these datasets insufficient to support the establishment of emission mitigation strategies. Thus, a fleet turnover model is developed in this study, and CO₂ emissions from global on-road vehicles from 1970 to 2020 are estimated for each country. Here, we analyze the evolution of the global vehicle stock over 50 years, identify the dominant emission contributors by vehicle and fuel type, and further characterize the age distribution of on-road CO₂ emissions. We find that trucks accounted for less than 5 % of global vehicle ownership but represented more than 20 % of on-road CO₂ emissions in 2020. The contribution of diesel vehicles to global on-road CO₂ emissions doubled during the 1970–2020 period, driven by the shift in the fuel-type distribution of vehicle ownership. The proportion of CO₂ emissions from vehicles in developing countries such as China and India in terms of global emissions from newly registered vehicles significantly increased after 2000, but global CO₂ emissions from vehicles that survived more than 15 years in 2020 still originated mainly from developed countries such as the United States and countries in the European Union.