Enhanced Light Absorption and Radiative Forcing by Black Carbon Agglomerates

The climate models of the Intergovernmental Panel on Climate Change list black carbon (BC) as an important contributor to global warming based on its radiative forcing (RF) impact. Examining closely these models, it becomes apparent that they might underpredict significantly the direct RF for BC, la...

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Bibliographic Details
Published in:Environmental science & technology 2022-06, Vol.56 (12), p.8610-8618
Main Authors: Kelesidis, Georgios A., Neubauer, David, Fan, Liang-Shih, Lohmann, Ulrike, Pratsinis, Sotiris E.
Format: Article
Language:English
Subjects:
Absorption
Agglomerates
Black carbon
Carbon
Climate change
Climate models
Dipoles
Electromagnetic absorption
Emissions
Energy and Climate
Global warming
Intergovernmental Panel on Climate Change
Light
Light scattering
Morphology
Optical analysis
Optical thickness
Radiative forcing
Refractivity
Satellite observation
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Summary:The climate models of the Intergovernmental Panel on Climate Change list black carbon (BC) as an important contributor to global warming based on its radiative forcing (RF) impact. Examining closely these models, it becomes apparent that they might underpredict significantly the direct RF for BC, largely due to their assumed spherical BC morphology. Specifically, the light absorption and direct RF of BC agglomerates are enhanced by light scattering between their constituent primary particles as determined by the Rayleigh–Debye–Gans theory interfaced with discrete dipole approximation and recent relations for the refractive index and lensing effect. The light absorption of BC is enhanced by about 20% by the multiple light scattering between BC primary particles regardless of the compactness of their agglomerates. The resulting light absorption agrees very well with the observed absorption aerosol optical depth of BC. ECHAM-HAM simulations accounting for the realistic BC morphology and its coatings reveal high direct RF = 3–5 W/m2 in East, South Asia, sub-Sahara, western Africa, and the Arabian peninsula. These results are in agreement with satellite and AERONET observations of RF and indicate a regional climate warming contribution by 0.75–1.25 °C, solely due to BC emissions.
ISSN:0013-936X
1520-5851
DOI:10.1021/acs.est.2c00428