Socioeconomic Analysis of Various Emission Pathways Considering the Uncertainties of Earth System Models

Abstract

Although much uncertainty exists in simulating future climate profiles with earth system models (ESMs), it has not been evaluated in relation to socioeconomic aspects. In this study, we analyze the socioeconomic impact of three emission pathways, all of which possibly achieve 4.5 W/m2 of radiative forcing in the year 2100 within uncertainties estimated by an ESM of intermediate complexity tuned for full ESMs using a computable general equilibrium model. The results indicate that the impacts are larger in the lower bound emission pathway to achieve 4.5 W/m2 as expected, although the economy and energy demand increase continuously in this century. However, the global primary energy demand in 2100 in the lower bound case is slightly larger than in the mean case; this can be interpreted because biomass energy with carbon capture and storage technology is enhanced to achieve very low carbon dioxide emissions in the lower bound case. In a comparison between the upper bound and lower bound emission pathways, the carbon price of the latter is approximately three times higher in 2100. The gross domestic product (GDP) in the latter is 4.1% smaller than that in the former in 2100, which is equivalent to only a 0.042% decrease in the annual GDP growth rate. Thus, the socioeconomic impacts caused by ESM uncertainties, here evaluated by GDP and energy demand, are not insignificant but are smaller than the differences in the emission pathways to achieve 4.5 W/m2.