Uncertainties in global aerosols and climate effects due to biofuel emissions

Abstract

Abstract. Aerosol emissions from biofuel combustion impact both health and climate; however, while reducing emissions through improvements to combustion technologies will improve health, the net effect on climate is largely unconstrained. In this study, we examine sensitivities in global aerosol concentration, direct radiative climate effect, and cloud-albedo aerosol indirect climate effect to uncertainties in biofuel emission factors, optical mixing-state, and model nucleation and background SOA. We use the Goddard Earth Observing System global chemical-transport model (GEOS-Chem) with TwO Moment Aerosol Sectional (TOMAS) microphysics. The emission factors include: amount, composition, size and hygroscopicity, as well as optical mixing-state properties. We also evaluate emissions from domestic coal use, which is not biofuel but is also frequently emitted from homes. We estimate the direct radiative effect assuming different mixing states (internal, core-shell, and external) with and without absorptive organic aerosol (brown carbon). We find the global-mean direct radiative effect of biofuel emissions ranges from −0.02 to +0.06 W m−2 across all simulation/mixing state combinations with regional effects in source regions ranging from −0.2 to +1.2 W m−2. The global-mean cloud-albedo aerosol indirect effect ranges from +0.01 to −0.02 W m−2 with regional effects in source regions ranging from −1.0 to −0.05 W m−2. The direct radiative effect is strongly dependent on uncertainties in emissions mass, composition, emissions aerosol size distributions and assumed optical mixing state, while the indirect effect is dependent on the emissions mass, emissions aerosol size distribution and the choice of model nucleation and secondary organic aerosol schemes. The sign and magnitude of these effects have a strong regional dependence. We conclude that the climate effects of biofuel aerosols are largely unconstrained, and the overall sign of the aerosol effects is unclear due to uncertainties in model inputs. This uncertainty limits our ability to introduce mitigation strategies aimed at reducing biofuel black carbon emissions in order to counter warming effects from greenhouse-gases. To better understand the climate impact of particle emissions from biofuel combustion, we recommend field/laboratory measurements to narrow constraints on: (1) emissions mass, (2) emission size distribution, (3) mixing state, and (4) ratio of black carbon to organic aerosol.

Radiative Effects of Residential Sector Emissions in China: Sensitivity to Uncertainty in Black Carbon Emissions

“…Several recent studies, mostly using global models, have focused specifically on the impact of BC and residential emissions on climate (e.g., Aunan et al, 2009;Butt et al, 2016;Kodros et al, 2015;Lacey & Henze, 2015). Using the GEOS-Chem model, Lacey and Henze (2015) estimated a total contribution to net global warming from cookstove emissions of 33 mK with model DRE and parameterized AIE.…”

“…Using the GEOS-Chem model, Lacey and Henze (2015) estimated a total contribution to net global warming from cookstove emissions of 33 mK with model DRE and parameterized AIE. Kodros et al (2015) used a cloud-resolving version of GEOS-Chem and estimated the global impacts of annual biofuel emissions results in an ERF of +0.35 W/m 2 . Kodros et al (2015) used a cloud-resolving version of GEOS-Chem and estimated the global impacts of annual biofuel emissions results in an ERF of +0.35 W/m 2 .…”

Synergistic Retrieval of Multitemporal Aerosol Optical Depth Over North China Plain Using Geostationary Satellite Data of Himawari‐8

“…Aerosol influences the climate via direct, indirect, and semidirect ways (Charlson et al, ; Forkel et al, ; Kaufman et al, ; Kaufman & Nakajima, ; Kiehl & Briegleb, ; Stevens, ; Twomey et al, ; Wang et al, ). Besides, atmospheric aerosol is considered as the primary source of uncertainty for the current Earth's anthropogenic radiative forcing (Archer‐Nicholls et al, ; Intergovernmental Panel on Climate Change (IPCC), ; Kodros et al, ; Li et al, ). Precise and consistent monitoring of aerosol distribution is required to reduce such uncertainty (Cheng et al, ).…”

Emission factors of health‐ and climate‐relevant pollutants measured in home during a carbon‐finance‐approved cookstove intervention in rural India

“…However, OC from biomass combustion also includes brown carbon, which absorbs light at shorter visible and UV wavelengths and may make a considerable contribution to warming [ Saleh et al , ]. While the magnitude of the net aerosol climate effect of current biofuel combustion is uncertain, it is likely climate warming [ Kodros et al , ; Lacey and Henze , ]. Also considering GHG emissions, especially methane and CO 2 from nonrenewable use of biomass [ Bailis et al , ], and other climate warming substances associated with emissions (e.g., ozone), traditional biofuel use is likely warming [ Unger et al , ; Grieshop et al , ].…”