Anthropogenic Greenhouse Gas Emissions, Growth, and Population Projections.

Greenhouse gas emissions and corresponding baseline projections of GDP and population growth are exogenous and taken from the Representative Concentration Pathway (RCP)/Shared Socio-Economic Pathway (SSP) database (40, 41). We match RCP3-PD/2.6 with SSP1, RCP4.5 with SSP2 and SSP5, RCP6 with SSP4, and RCP8.5 with SSP5. Since we estimate the SCC, it is important that our emissions scenarios extend beyond 2100. Therefore, we use the Extended Concentration Pathways database for emissions (42) and develop a method of extending the corresponding SSPs beyond 2100 (SI Appendix). CO2 and CH4 emissions are modeled explicitly. Other GHGs and forcing agents are combined into an exogenous vector of residual radiative forcing.