How much can the vertical distribution of black carbon affect its global direct radiative forcing?

Zarzycki, Colin M.; Bond, Tami C.

doi:10.1029/2010gl044555

Cited by 157 publications

(141 citation statements)

References 42 publications

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“…That estimate includes both a gross 15 % global downscaling of BC forcing efficiency due to overestimation of BC aloft, and a differentiated regional upscaling of emissions derived by comparing aerosol absorption optical depth from AeroCom Phase I with that from AERONET ground-based remote sensing. Their downscaling, based on recent model studies (Bond et al, 2013;Samset and Myhre, 2011;Zarzycki and Bond, 2010) and evaluation of AeroCom Phase I results (Schwarz et al, 2010), is comparable to our 25 % reduction in forcing, though our reduction is attributed to remote ocean areas. For near-source and remote regions covered in the present study we here find no need for an emission bias-related upscaling; however the present data do not cover the regions where the upscaling in that analysis (Bond et al, 2013) was most pronounced.…”

Section: Consequences For Modelled Bc Ff + Fb Rfmentioning

confidence: 58%

“…The uncertainty ranges (5-95 %) show that BC is still a major contributor to the total uncertainty on anthropogenic RF. Further, it has recently been shown that, because the direct RF per unit mass BC increases strongly with altitude (Ban-Weiss et al, 2011;Zarzycki and Bond, 2010;Samset and Myhre, 2011), the diversity in modelled vertical profiles of BC concentration in the AeroCom Phase II models may account for up to 50 % of the model diversity in anthropogenic BC RF . Climate model simulations, however, indicate that, while direct BC forcing strengthens with altitude, its climate efficacy may decrease, i.e.…”

Section: Introductionmentioning

confidence: 99%

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Modelled black carbon radiative forcing and atmospheric lifetime in AeroCom Phase II constrained by aircraft observations

et al. 2014

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Abstract. Atmospheric black carbon (BC) absorbs solar radiation, and exacerbates global warming through exerting positive radiative forcing (RF). However, the contribution of BC to ongoing changes in global climate is under debate. Anthropogenic BC emissions, and the resulting distribution of BC concentration, are highly uncertain. In particular, longrange transport and processes affecting BC atmospheric lifetime are poorly understood. Here we discuss whether recent assessments may have overestimated present-day BC radiative forcing in remote regions. We compare vertical profiles of BC concentration from four recent aircraft measurement campaigns to simulations by 13 aerosol models participating in the AeroCom Phase II intercomparison. An atmospheric lifetime of BC of less than 5 days is shown to be essential for reproducing observations in remote ocean regions, in line with other recent studies. Adjusting model results to measurements in remote regions, and at high altitudes, leads to a 25 % reduction in AeroCom Phase II median direct BC forcing, from fossil fuel and biofuel burning, over the industrial era. The sensitivity of modelled forcing to BC vertical profile and lifetime highlights an urgent need for further flight campaigns, close to sources and in remote regions, to provide improved quantification of BC effects for use in climate policy.

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Section: Consequences For Modelled Bc Ff + Fb Rfmentioning

confidence: 58%

Section: Introductionmentioning

confidence: 99%

Modelled black carbon radiative forcing and atmospheric lifetime in AeroCom Phase II constrained by aircraft observations

et al. 2014

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“…Further analyses are planned. Within the framework of the AeroCom Phase II intercomparison (Myhre et al, 2012), it will be interesting to investigate issues like the regional responses to anthropogenic aerosol forcing, and modeling uncertainties in the distribution and absorption properties of black carbon (Zarzycki and Bond, 2011;Samset and Myhre, 2011;Stier et al, 2007).…”

Section: Direct Radiative Effect Of Aerosolsmentioning

confidence: 99%

“…Langner and Rodhe, 1991;Feichter et al, 1996) gradually led to appreciation of the importance of microphysics in aerosol modelling. The newer models have thus included more detailed descriptions of aerosol composition and size distribution, using different approaches (Wilson et al, 2001;Jacobson, 2001;Vignati et al, 2004;Easter et al, 2004;Stier et al, 2005;Spracklen et al, 2005;Liu et al, 2005;Bauer et al, 2008;Liu et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

The global aerosol-climate model ECHAM-HAM, version 2: sensitivity to improvements in process representations

et al. 2012

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Abstract. This paper introduces and evaluates the second version of the global aerosol-climate model ECHAM-HAM. Major changes have been brought into the model, including new parameterizations for aerosol nucleation and water uptake, an explicit treatment of secondary organic aerosols, modified emission calculations for sea salt and mineral dust, the coupling of aerosol microphysics to a two-moment stratiform cloud microphysics scheme, and alternative wet scavenging parameterizations. These revisions extend the model's capability to represent details of the aerosol lifecycle and its interaction with climate. Nudged simulations of the year 2000 are carried out to compare the aerosol properties and global distribution in HAM1 and HAM2, and to evaluate them against various observations. Sensitivity experiments are performed to help identify the impact of each individual update in model formulation.Results indicate that from HAM1 to HAM2 there is a marked weakening of aerosol water uptake in the lower troposphere, reducing the total aerosol water burden from 75 Tg to 51 Tg. The main reason is the newly introduced κ-Köhler-theory-based water uptake scheme uses a lower value for the maximum relative humidity cutoff. Particulate organic matter loading in HAM2 is considerably higher in the upper troposphere, because the explicit treatment of secondary organic aerosols allows highly volatile oxidation products of the precursors to be vertically transported to regions of very low temperature and to form aerosols there. Sulfate, black carbon, particulate organic matter and mineral dust in HAM2 have longer lifetimes than in HAM1 because of weaker incloud scavenging, which is in turn related to lower autoconversion efficiency in the newly introduced two-moment cloud microphysics scheme. Modification in the sea salt emission scheme causes a significant increase in the ratio (from 1.6 to 7.7) between accumulation mode and coarse mode emission fluxes of aerosol number concentration. This leads to a general increase in the number concentration of smaller particles over the oceans in HAM2, as reflected by the higher Angström parameters.Evaluation against observation reveals that in terms of model performance, main improvements in HAM2 include a marked decrease of the systematic negative bias in the absorption aerosol optical depth, as well as smaller biases over the oceans inÅngström parameter and in the accumulation mode number concentration. The simulated geographical distribution of aerosol optical depth (AOD) is better correlated with the MODIS data, while the surface aerosol mass concentrations are very similar to those in the old version. The total aerosol water content in HAM2 is considerably Published by Copernicus Publications on behalf of the European Geosciences Union. K. Zhang et al.: Aerosol properties in ECHAM-HAM2closer to the multi-model average from Phase I of the AeroCom intercomparison project. Model deficiencies that require further efforts in the future include (i) positive biases in AOD over the ocean, (ii) n...

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“…However, the diversity in existing estimates of the climate effect of BC is large (Bond et al, 2013;Boucher et al, 2013;Myhre et al, 2013). The causes for the diversity in estimates are many, from emissions (Amann et al, 2013;Cohen and Wang, 2014;Lam et al, 2012;Stohl et al, 2013;Wang et al, 2014b), lifetime and abundance (Hodnebrog et al, 2014;Samset et al, 2014;Wang et al, 2014a) to radiative efficiency Zarzycki and Bond, 2010).…”

Section: Introductionmentioning

confidence: 99%

Standard climate models radiation codes underestimate black carbon radiative forcing

Myhre

Samset

2015

Atmos. Chem. Phys.

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Abstract. Radiative forcing (RF) of black carbon (BC) in the atmosphere is estimated using radiative transfer codes of various complexities. Here we show that the two-stream radiative transfer codes used most in climate models give too strong forward scattering, leading to enhanced absorption at the surface and too weak absorption by BC in the atmosphere. Such calculations are found to underestimate the positive RF of BC by 10 % for global mean, all sky conditions, relative to the more sophisticated multi-stream models. The underestimation occurs primarily for low surface albedo, even though BC is more efficient for absorption of solar radiation over high surface albedo.

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How much can the vertical distribution of black carbon affect its global direct radiative forcing?

Cited by 157 publications

References 42 publications

Modelled black carbon radiative forcing and atmospheric lifetime in AeroCom Phase II constrained by aircraft observations

Modelled black carbon radiative forcing and atmospheric lifetime in AeroCom Phase II constrained by aircraft observations

The global aerosol-climate model ECHAM-HAM, version 2: sensitivity to improvements in process representations

Standard climate models radiation codes underestimate black carbon radiative forcing

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