Do Different Emission Pathways Under Fixed Cumulative CO2 Emissions affect Socioeconomic Conditions?

Cumulative carbon dioxide (CO2) emissions have become a good indicator of increases in the global mean temperature. This study evaluates the relationship between cumulative CO2 emissions, their pathways, and their socioeconomic impacts. We analyzed multiple emission pathways that achieve three cumulative emission levels using a computable general equilibrium model with cumulative emissions equivalent to the 2ºC target, the 2ºC target plus 10%, and the representative concentration pathway of 4.5 W/m2. Although the cumulative emission figures are identical, the resulting impacts vary depending on the pathway used. For example, the 95% confidence interval of cumulative global gross domestic product (GDP) (2010–2100; discount rate: 5%) for the 2ºC target is 1355–1363 trillion USD. However, the observed differences are small compared to those for different cumulative emissions. The year emission reduction starts also affects cumulative GDP. The cumulative GDP of pathways with later starting years grows weaker (5% significance level). Furthermore, emission levels in 2100 share a number of correlations with the socioeconomic factors highlighted in this study. For example, emission levels have a strong positive correlation with GDP in 2100 (r = 0.93 for the 2ºC target), whereas they have only a moderate negative correlation with cumulative GDP. They also have a strong negative correlation with the cumulative energy demand (r = -0.93). These results suggest that different pathways toward cumulative emissions in this century will affect the resulting cumulative socioeconomic impacts. Earlier emission reduction is effective in realizing higher GDP and increases the probability of achieving ambitious climate targets