New climate scenario framework implementation in the GCAM integrated assessment model

Abstract

This report has various objectives: (i) to provide an overview of the climate Integrated Assessment approach; (ii) to describe the Global Climate Assessment Model (GCAM); (iii) to outline the new IPCC scenario framework represented by the Shared Socio-economic Pathways (SSPs) and the Representative Concentration Pathways (RCPs); and (iv) to document the implementation of the new scenario framework in version 3.1 of the GCAM. The GCAM baseline is thus calibrated to the “Middle of the Road” or SSP2 scenario using the data calculated by the OECD. The implications of this scenario are important because it will probably become a standard scenario among the research community. The exogenous variables, the implications for income convergence and the results in terms of energy mix, emissions, temperature and radiative forcing of SSP2 implementation in the GCAM are presented at both global and regional levels. These results are also compared with the GCAM-Reference baseline and the IPCC SRES representative scenarios. Then the feasibility, cost and implications of a climate policy that seeks to stabilize temperature at 2ºC (2.6 W/m2 RCP) using a global uniform carbon tax are analyzed. The study is completed by a decomposition analysis that enables the main driving factors of CO2 variation to be identified, including population, affluence, energy intensity, carbon intensity and fossil-fuel share of the energy mix. Finally we draw some conclusions and highlight points for further research.