The Social Costs of Aviation: Comparing Contrail Cirrus and CO2

Abstract Aviation contrail cirrus has important climate impacts. To construct efficient policies to reduce the uncertain, heterogeneous and short-lived climate impacts of contrail cirrus and balance these against the certain, homogeneous and long-lived climate impact of CO₂ emissions the climate impact of CO₂ and contrail cirrus need to be placed on a common scale. We analyze the social cost of CO₂and of contrail cirrus as well their ratio using an updated version of the Dynamic Integrated Climate Economy (DICE) model with three different discount rates and three different future climate pathways. The social cost of contrail cirrus is less sensitive to the discount rate and less affected by the long-term temperature pathway than the social cost of CO₂. However, the social cost of contrail cirrus is strongly dependent on specific meteorological conditions, which makes the social cost associated with individual flights vary by several orders of magnitude.