Sensitivity of tropospheric oxidants to biomass burning emissions: implications for radiative forcing

[1] Biomass burning is one of the largest sources of trace gases and aerosols to the atmosphere and has profound influence on tropospheric oxidants and radiative forcing. Using a fully coupled chemistry-climate model (GFDL AM3), we find that co-emission of trace gases and aerosol from present-day biomass burning increases the global tropospheric ozone burden by 5.1% and decreases global mean OH by 6.3%. Gas and aerosol emissions combine to increase CH4 lifetime nonlinearly. Heterogeneous processes are shown to contribute partly to the observed lower ΔO3/ ΔCO ratios in northern high latitudes versus tropical regions. The radiative forcing from biomass burning is shown to vary nonlinearly with biomass burning strength. At present-day emission levels, biomass burning produces a net radiative forcing of 0.19 W/m ( 0.29 from short-lived species, mostly aerosol direct and indirect effects, +0.10 from CH4and CH4-induced changes in O3 and stratospheric H2O) but increases emissions to over 5 times present levels would result in a positive net forcing. Citation: Mao, J., L. W. Horowitz, V. Naik, S. Fan, J. Liu, and A. M. Fiore (2013), Sensitivity of tropospheric oxidants to biomass burning emissions: implications for radiative forcing, Geophys. Res. Lett., 40, 1241–1246, doi:10.1002/grl.50210.