Internalization of the external costs of global environmental damage in an integrated assessment model

This study simulates the internalization of the external costs of major global environmental issues using an optimal economic growth model. We merged two existing models: an integrated assessment model (IAM) and a life-cycle impact assessment (LCIA) model. We sought to achieve simultaneously the following three objectives: (i) to incorporate environmental issues including global warming in the IAM; (ii) to assess environmental impacts with a bottom-up approach from the LCIA; and (iii) to internalize external costs obtained from the environmental impact study. The study also provides initial simulation results obtained from the merged model. Simulation results indicate that global warming will account for somewhere from 10% to 40% of all external costs in the 21st century. The remaining cost will come from land use and its changes. The internalization of the external cost will cause a decline in economic growth by approximately 5%, whereas forest preservation will increase by 40% and fossil-fuel consumption will be reduced by 15%. The estimated sustainability indicators imply that a necessary condition of sustainable development is satisfied for the entire world and for the developed countries during the 21st century, but is not satisfied until the latter half of this century for the developing counties.