AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
Unconstrained Climate Impacts of Biofuel Combustion Due to Uncertain Carbonaceous Radiative and Cloud Effects
JOHN KODROS, Catherine Scott, Salvatore Farina, Lee Yunha, Christian L'Orange, John Volckens, Jeffrey R. Pierce, Colorado State University
Abstract Number: 38 Working Group: Carbonaceous Aerosols in the Atmosphere
Abstract Prevalent combustion of biofuel as a source of energy for domestic tasks emits large quantities of black carbon and organic aerosol, causing potentially large impacts to air quality and climate. While reducing aerosol emissions through improving technologies is a necessary step for improving health and lifestyle in developing regions, the net effect on climate is largely unconstrained due to large uncertainties surrounding black carbon’s radiative and cloud effects. We use the chemical transport model, GEOS-Chem, with TOMAS microphysics to explore the sensitivity of the direct and cloud-albedo indirect effects due to uncertainties from black and organic carbon emission factors, optical mixing state, and modeled nucleation and background secondary organic aerosol. We find the direct radiative effect is strongly dependent on assumed mixing state, absorptivity of organic aerosol (brown carbon), and the emissions BC to OA ratio, while the cloud-albedo indirect effect is strongly dependent on emissions mass, aerosol size distribution, and choice of model nucleation and secondary organic aerosols. In the global average, the direct effect ranges from -0.02 to +0.06 W m$^(-2) and the indirect effect ranges from +0.01 to -0.02 W m$^(-2), with larger magnitude effects in source regions. We find the sign of the net climate effect from biofuel combustion emissions uncertain, thus substantially limiting our ability to introduce mitigation strategies aimed at reducing black carbon to counter warming effects from greenhouse gases.