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| Titel |
Uncertainties in global aerosols and climate effects due to biofuel emissions |
| VerfasserIn |
J. K. Kodros, C. E. Scott, S. C. Farina, Y. H. Lee, C. L'Orange, J. Volckens, J. R. Pierce |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 15, no. 15 ; Nr. 15, no. 15 (2015-08-03), S.8577-8596 |
| Datensatznummer |
250119943
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| Publikation (Nr.) |
 copernicus.org/acp-15-8577-2015.pdf |
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| Zusammenfassung |
| 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 secondary organic aerosol (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 (homogeneous,
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 +0.8 W m−2. The global-mean cloud-albedo aerosol indirect effect (AIE) 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. |
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