Estimating the social cost of non-CO2 GHG emissions: Methane and nitrous oxide

Many estimates of the social cost of CO2 emissions (SCCO2) can be found in the climate economics literature. However, to date few estimates of the social costs of other greenhouse gases have been published, and most are not comparable to current estimates of the SCCO2. We construct an integrated assessment model that combines MAGICC and economic components from DICE to estimate the social costs of CO2, CH4, and N2O for the years 2010–2050, using assumptions similar to the recent U.S. government interagency SCC working group. We compare our estimates of the social costs for non-CO2 gases to those produced using the SCCO2 to value “CO2-equivalent” emissions, calculated using global warming potentials (GWPs). We examine the estimation error associated with using GWPs for single- and multi-gas abatement policies. In both cases the error can be large, so estimates of the social costs of these gases should be used whenever possible. However, if direct estimates are not available the value of reductions estimated using GWPs will typically have lower absolute errors than default estimates of zero, and provide lower bounds of the abatement benefits.