of 41
Article
Microphysical complexity of black carbon particles
restricts their warming potential
Graphical abstract
Highlights
d
Inadequate BC microphysics understanding hinders its
climate assessment
d
Coating heterogeneity and morphology co-explain the lower
BC absorption by

50%
d
Off-center BC-core position is also an essential factor in
absorption gap
d
Integrating an observation-based framework in this model
reduces global BC DRF by up to 23%
Authors
Xiao-Feng Huang, Yan Peng,
Jing Wei, ..., Hongjun Mao,
John H. Seinfeld, Yuan Wang
Correspondence
pengjianfei@nankai.edu.cn (J.P.),
hely@pku.edu.cn (L.-Y.H.),
yzwang@stanford.edu (Y.W.)
In brief
The warming effect of black carbon (BC)
is uncertain due to a persistent model-
measurement gap in light absorption
enhancement. Here, we reveal multi-level
microphysical complexities in BC-
containing particles, and these explain
the lower observed BC absorption. In
addition to coating heterogeneity and
non-spherical shape, the off-center BC-
core position is also an essential factor in
the absorption gap. When considering
the observation-based framework in the
BC microphysical representation, BC’s
global direct radiative forcing reduces by
up to 23%.
Huang et al., 2024, One Earth
7
, 136–145
January 19, 2024
ª
2023 The Author(s). Published by Elsevier Inc.
https://doi.org/10.1016/j.oneear.2023.12.004
ll
Article
Microphysical complexity of black carbon particles
restricts their warming potential
Xiao-Feng Huang,
1
,
6
Yan Peng,
1
,
6
Jing Wei,
1
,
6
Jianfei Peng,
2
,
7
,
*
Xiao-Yu Lin,
1
Meng-Xue Tang,
1
Yong Cheng,
1
Zhengyu Men,
2
Tiange Fang,
2
Jinsheng Zhang,
2
Ling-Yan He,
1
,
*
Li-Ming Cao,
1
Chao Liu,
3
Chenchong Zhang,
4
Hongjun Mao,
2
John H. Seinfeld,
5
and Yuan Wang
4
,
*
1
Laboratory of Atmospheric Observation Supersite, School of Environment and Energy, Peking University Shenzhen Graduate School,
Shenzhen 518055, China
2
Tianjin Key Laboratory of Urban Transport Emission Research & State Environmental Protection Key Laboratory of Urban Ambient Air
Particulate Matter Pollution Prevention and Control, College of Environmental Science and Engineering, Nankai University, Tianjin
300071, China
3
Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters, Nanjing University of Information Science &
Technology, Nanjing 210044, China
4
Department of Earth System Science, Stanford University, Stanford, CA 94305, USA
5
Divisions of Chemistry and Chemical Engineering and Engineering and Applied Science, California Institute of Technology, Pasadena,
CA, USA
6
These authors contributed equally
7
Lead contact
*Correspondence:
pengjianfei@nankai.edu.cn
(J.P.),
hely@pku.edu.cn
(L.-Y.H.),
yzwang@stanford.edu
(Y.W.)
https://doi.org/10.1016/j.oneear.2023.12.004
SUMMARY
Black carbon (BC) strongly absorbs solar radiation, but its warming effect on climate is poorly quantified. A
key challenge is to accurately assess BC light absorption after BC is mixed with non-BC components. How-
ever, there has consistently been a large observation-modeling gap in BC light absorption estimation, reflect-
ing the insufficient understanding of realistic BC complexity. Here, we conduct comprehensive
in situ
mea-
surements of BC single-particle microphysics, e.g., size, coating amounts, density, and shape, along with
optical closure calculation. Specifically, the observed particle-to-particle heterogeneities in size and coating
and the non-spherical BC shape only explain the lower observed BC absorption by

20% and

30%, respec-
tively. A remaining gap for fully aged spherical BC-containing particles is related to the off-center BC-core
position. The global climate model assessment shows that fully accounting for the observed BC complexity
in the aerosol microphysical representation reduces the global BC direct radiative forcing by up to 23%.
INTRODUCTION
Black carbon (BC) is ubiquitous in the atmosphere and profoundly
affects global and regional climate owing to its efficient radiative
absorption capacity.
1–3
The direct radiative forcing (DRF) of BC
particles represents one of the largest sources of uncertainty in
present and future climate assessments.
4
Estimation of BC DRF
depends explicitly on the particle’s light absorption cross-section,
which is further determined by the mixing state of BC with non-BC
materials.
5–8
A widely adopted assumption of the mixing state in
SCIENCE FOR SOCIETY
Black carbon (BC) strongly absorbs solar radiation, but its warming effect is still
highly uncertain. One crucial uncertainty stems from insufficient understanding of BC microphysics and op-
tics, which is evident as the constant model-measurement discrepancy in BC light absorption enhancement
in previous studies. Therefore, characterizing the complexity of BC microphysics in the realistic atmosphere
is essential for constraining BC light absorption ability. Here, we present direct observations of the micro-
physical properties of individual particles across the entire BC-containing particle population, providing
unique insight into multi-level BC microphysical heterogeneity that largely reconciles the model-measure-
ment gap. Our observation-based framework facilitates in-depth assessment of BC environmental and
climate effects in measurement and model studies.
136
One Earth
7
, 136–145, January 19, 2024
ª
2023 The Author(s). Published by Elsevier Inc.
This is an open access article under the CC BY-NC license (
http://creativecommons.org/licenses/by-nc/4.0/
).
ll
OPEN ACCESS