Effective Radiative forcing from emissions of reactive gases and aerosols - a multimodel comparison.

This paper quantifies the effective radiative forcing from CMIP6 models of the present-day anthropogenic emissions of NO_x, CO, VOCs, SO₂, NH₃, black carbon and primary organic carbon. Effective radiative forcing from pre-industrial to present-day changes in the concentrations of methane, N₂O and halocarbons are quantified and attributed to their anthropogenic emissions. Emissions of reactive species can cause multiple changes in the composition of radiatively active species: tropospheric ozone, stratospheric ozone, secondary inorganic and organic aerosol and methane. We therefore break down the ERFs from each emitted species into the contributions from the composition changes. The 1850 to 2014 mean ERFs are 1.1 ± 0.07 W m^-2 for sulfate, -0.24 ± 0.01 W m^-2 for organic carbon (OC), and 0.15 ± 0.04 W m^-2 for black carbon (BC), and for the aerosols combined it is -0.95 ± 0.03 W m^-2. The means for the reactive gases are 0.69 ± 0.04 W m^-2 for methane (CH₄), 0.06 ± 0.04 W m^-2 for NO_x, -0.09 ± 0.03 W m^-2 for volatile organic carbons (VOC), 0.16 ± 0.03 W m^-2 for ozone (O₃), 0.27 W m^-2 for nitrous oxide (N₂O) and -0.02 ± 0.06 W m^-2 for hydrocarbon (HC). Differences in ERFs calculated for the different models reflect differences in the complexity of their aerosol and chemistry schemes, especially in the case of methane where tropospheric chemistry captures increased forcing from ozone production. [ABSTRACT FROM AUTHOR]