AAAR 33rd Annual Conference
October 20 - October 24, 2014
Rosen Shingle Creek
Orlando, Florida, USA
Abstract View
Uncertainties in Global Aerosol and Climate Forcings from Biofuel Emissions
JOHN KODROS, Catherine Scott, Salvatore Farina, Jeffrey Pierce, Colorado State University
Abstract Number: 32 Working Group: Carbonaceous Aerosols in the Atmosphere
Abstract Prevalent use of biofuel as a source of energy for domestic tasks has created concerns for air quality and climate. Successful interventions of improved combustion devices decreases emitted particle concentrations and improves air quality. The net effect of changing emission scenarios on climate remains uncertain. Combustion of wood, agricultural waste, and dung emits black (BC) and organic carbon (OC). BC and OC can alter climate through absorption and scattering (direct effect), altering cloud properties (indirect effect), and altering the temperature profile (semi-direct effect). Recent studies have focused on the positive direct effect from black carbon absorption. Black carbon can also have a cooling effect when activated as a cloud condensation nuclei. The net forcing from BC and OC is dependent on emission mass, size distribution and chemical mixing state. To test the sensitivity of particle number and aerosol radiative forcing to these uncertainties we run a sensitivity study using GEOS-Chem-TOMAS. With the current emission dataset we find biofuel emissions contribute close to 25% of global BC and OC mass. In heavy source regions biofuel contributes more than half of total BC and OC mass. Altering the size distribution leads to changes in particle number of around 10% in source regions. The sensitivity of aerosol number from uncertainties in size are on the same order of removing biofuel emissions. The aerosol indirect effect is dependent on particle number which in turn is dependent on emitted size distribution. Thus, while it is clear combustion improvements will lead to improvements to health, the net result on climate remains uncertain.