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Intro How well do models simulate BC? BC radiative effects BC effects on ice clouds Conclusions Extra
Climate Effects of Black Carbon Aerosols
Ulrike Lohmann
ETH Zurich
Institute for Atmospheric
and Climate Science
Acknowledgements:
Zamin Kanji and Andre Welti
Ulrike Lohmann (IACETH) BC climate effects ETH Zurich, June 24, 2014 1 / 16
Intro How well do models simulate BC? BC radiative effects BC effects on ice clouds Conclusions Extra
Bond et al., JGR (2013)
Ulrike Lohmann (IACETH) BC climate effects ETH Zurich, June 24, 2014 2 / 16
Intro How well do models simulate BC? BC radiative effects BC effects on ice clouds Conclusions Extra
(a)
(c)
(a) (b)
(d)(c)
Scattering aerosols
Aerosol-radiation interactions
Absorbing aerosols
CoolingThe atmospheric circulation and mixing processes spread the cooling regionally and in the vertical.
Aerosols scatter solar radiation. Less solar radiation reaches the surface, which leads to a localised cooling.
At the larger scale there is a net warming of the surface and atmosphere because the atmospheric circulation and mixing processes redistribute the thermal energy.
WarmingAerosols absorb solar radiation. This heats the aerosol layer but the surface, which receives less solar radiation, can cool locally.
IPCC, Fig. FAQ 7.2, (2013)
Ulrike Lohmann (IACETH) BC climate effects ETH Zurich, June 24, 2014 3 / 16
Intro How well do models simulate BC? BC radiative effects BC effects on ice clouds Conclusions Extra
Vertical profiles of BC
Pres
sure
(hPa
)
1000
Pres
sure
(hPa
)
0.01 0.1 1 10 100 1000BC MMR (ng kg-1)
0.01 0.1 1 10 100 1000BC MMR (ng kg-1)
GMI GOCART
IMPACT INCA ECHAM5-HAM
SPRINTARS TM5
OsloCTM2 BCC CAM4-Oslo CAM5.1 HadGEM2
GISS-MATRIX GISS-modelE
600
200
1000
600
200
HIPPO-1 (Jan 2009)20ºS - 20ºN
HIPPO-1 (Jan 2009)60ºS - 20ºS
A-FORCE (Mar-Apr. 2009)26ºN - 38ºN
HIPPO-1 (Jan 2009)20ºN - 60ºN
Fig. 7.15 (IPCC, 2013)
Ulrike Lohmann (IACETH) BC climate effects ETH Zurich, June 24, 2014 4 / 16
Intro How well do models simulate BC? BC radiative effects BC effects on ice clouds Conclusions Extra
Transport to the Arctic
Bourgeouis and Bey, JGR (2011)
Ulrike Lohmann (IACETH) BC climate effects ETH Zurich, June 24, 2014 5 / 16
Intro How well do models simulate BC? BC radiative effects BC effects on ice clouds Conclusions Extra
Bond et al., JGR (2013)
Ulrike Lohmann (IACETH) BC climate effects ETH Zurich, June 24, 2014 6 / 16
Intro How well do models simulate BC? BC radiative effects BC effects on ice clouds Conclusions Extra
Aerosol radiative forcing 1750-2010
��
���
���
RFar
i (W
m-2)
Sulphate
POA FFBB
SOA
Nitrate
Mineral
Total
BC FF
hatched: Aero-
Com II models
solid: AR5 esti-
mates
(IPCC, Fig. 7.18,
2013)
Ulrike Lohmann (IACETH) BC climate effects ETH Zurich, June 24, 2014 7 / 16
Intro How well do models simulate BC? BC radiative effects BC effects on ice clouds Conclusions Extra
Bond et al., JGR (2013)
Ulrike Lohmann (IACETH) BC climate effects ETH Zurich, June 24, 2014 8 / 16
Intro How well do models simulate BC? BC radiative effects BC effects on ice clouds Conclusions Extra
Bond et al., JGR (2013)
Ulrike Lohmann (IACETH) BC climate effects ETH Zurich, June 24, 2014 9 / 16
Intro How well do models simulate BC? BC radiative effects BC effects on ice clouds Conclusions Extra
Bond et al., JGR (2013)
Ulrike Lohmann (IACETH) BC climate effects ETH Zurich, June 24, 2014 10 / 16
Intro How well do models simulate BC? BC radiative effects BC effects on ice clouds Conclusions Extra
Heterogeneous freezing
Hoose and Mohler, ACP (2012)
Ulrike Lohmann (IACETH) BC climate effects ETH Zurich, June 24, 2014 11 / 16
Intro How well do models simulate BC? BC radiative effects BC effects on ice clouds Conclusions Extra
Compilation of freezing data on soot
Hoose and Mohler, ACP (2012)
Ulrike Lohmann (IACETH) BC climate effects ETH Zurich, June 24, 2014 12 / 16
Intro How well do models simulate BC? BC radiative effects BC effects on ice clouds Conclusions Extra
Ice nucleation active surface site (INAS) density
Hoose and Mohler, ACP (2012)
Ulrike Lohmann (IACETH) BC climate effects ETH Zurich, June 24, 2014 13 / 16
Intro How well do models simulate BC? BC radiative effects BC effects on ice clouds Conclusions Extra
Frozen fraction of droplets containing BC
233 234 235 236 237 238 239 240 241 242 2430.0
0.2
0.4
0.6
0.8
1.0 100 nm 200 nm 400 nm
Froz
en fr
actio
n
Temperature (K)
Regal Black
233 234 235 236 237 238 239 240 241 242 2430.0
0.2
0.4
0.6
0.8
1.0 100 nm 200 nm 400 nm
Froz
en fr
actio
n
Temperature (K)
GFG spark generator
233 234 235 236 237 238 239 240 241 242 2430.0
0.2
0.4
0.6
0.8
1.0 100 nm 200 nm 400 nm
Froz
en F
ract
ion
Temperature (K)
Fullerene
233 234 235 236 237 238 239 240 241 242 2430.0
0.2
0.4
0.6
0.8
1.0 100 nm 200 nm 400 nm
Froz
en fr
actio
n
Temperature (K)
Cast Black
233 234 235 236 237 238 239 240 241 242 2430.0
0.2
0.4
0.6
0.8
1.0Cast Brown
200 nm 400 nm
Froz
en fr
actio
n
Temperature (K)
Courtesy Andre Welti and Zamin Kanji (ETHZ)
Ulrike Lohmann (IACETH) BC climate effects ETH Zurich, June 24, 2014 14 / 16
Intro How well do models simulate BC? BC radiative effects BC effects on ice clouds Conclusions Extra
Conclusions
BC as ice nuclei:
! BC nucleates ice only at rather cold temperatures
! The studies testing BC as an ice nuclei obtain conflicting results
Climate effects of BC:
! The total climate forcing of BC is positive, but could be close to zero
if co-emitted species are considered as well
! The effect of BC on clouds seems to counteract its direct radiative
effect, but they are much more uncertain
Ulrike Lohmann (IACETH) BC climate effects ETH Zurich, June 24, 2014 15 / 16
Intro How well do models simulate BC? BC radiative effects BC effects on ice clouds Conclusions Extra
BC-rich sources comprise 99% of
all BC emissions
! Top bar: direct forcing by
aerosol and most gases and
aerosol cryosphere forcing
! Middle bar: cloud effects
and nitrate
! Bottom bar: net climate
forcing by each emission
source
Bond et al., JGR (2013)
Ulrike Lohmann (IACETH) BC climate effects ETH Zurich, June 24, 2014 16 / 16
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