Radiative forcing of the direct aerosol effect from AeroCom Phase II simulations

Myhre, Gunnar; Samset, B. H.; Schulz, Mıchael; Balkanski, Yves; Bauer, Susanne E.; Berntsen, Terje; Bian, Huisheng; Bellouin, Nicolas; Chin, Mian; Diehl, Thomas; Easter, Richard C.; Feichter, J.; Ghan, S. J.; Hauglustaine, Didier; Iversen, Trond; Kinne, Stefan; Kirkevåg, Alf; Lamarque, J. F.; Lin, Guang; Liu, X.; Luo, Gan; Ma, Xingxing; Penner, J. E.; Rasch, Philip J.; Seland, Øyvind; Skeie, Ragnhild Bieltvedt; Stier, Philip; Takemura, Toshihiko; Tsigaridis, Kostas; Wang, Z.; Xu, Li; Yu, Hongbin; Yu, Fangqun; Yoon, Jin‐Ho; Zhang, K.; Zhang, H.; Zhou, Cheng

doi:10.5194/acpd-12-22355-2012

Cited by 104 publications

(171 citation statements)

References 83 publications

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“…Our measured maximum absorption enhancement factor of 2.4 in Beijing is larger than those commonly adopted in global climate models (12,(27)(28)(29). To assess the climatic implications of BC aging, our measured absorption enhancement is used to estimate DRF on the basis of simulations from the previous global climate models (12).…”

Section: Significancementioning

confidence: 99%

Markedly enhanced absorption and direct radiative forcing of black carbon under polluted urban environments

Peng

Guo

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

516

479

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Black carbon (BC) exerts profound impacts on air quality and climate because of its high absorption cross-section over a broad range of electromagnetic spectra, but the current results on absorption enhancement of BC particles during atmospheric aging remain conflicting. Here, we quantified the aging and variation in the optical properties of BC particles under ambient conditions in Beijing, China, and Houston, United States, using a novel environmental chamber approach. BC aging exhibits two distinct stages, i.e., initial transformation from a fractal to spherical morphology with little absorption variation and subsequent growth of fully compact particles with a large absorption enhancement. The timescales to achieve complete morphology modification and an absorption amplification factor of 2.4 for BC particles are estimated to be 2.3 h and 4.6 h, respectively, in Beijing, compared with 9 h and 18 h, respectively, in Houston. Our findings indicate that BC under polluted urban environments could play an essential role in pollution development and contribute importantly to large positive radiative forcing. The variation in direct radiative forcing is dependent on the rate and timescale of BC aging, with a clear distinction between urban cities in developed and developing countries, i.e., a higher climatic impact in more polluted environments. We suggest that mediation in BC emissions achieves a cobenefit in simultaneously controlling air pollution and protecting climate, especially for developing countries.black carbon | absorption | air quality | radiative forcing | climate B lack carbon (BC) particles, produced from incomplete fossil fuel combustion and biomass burning, are ubiquitous in the atmosphere and have profound impacts on air quality and climate (1-4). As a key short-lived climate forcer, the magnitude of BC direct radiative forcing (DRF) is dependent on the mixing state, i.e., whether particles are externally or internally mixed with other aerosol types (5, 6), and atmospheric aging by coating with secondary aerosol constituents (such as organics and sulfate) enhances the mass absorption cross-section (MAC) (5-9). Previous laboratory studies conducted under controlled experimental conditions yielded a broad range of MAC enhancements from 1.05 to 3.50, varying with the diameter, morphology, and coating of BC particles (7-15). On the other hand, a field measurement indicated a negligible absorption enhancement of ambient BC particles under a variable mixing state (16). In addition, BC aging and absorption enhancement also strongly impact visibility and atmospheric stability.Few direct measurements have been conducted to capture aging and quantify the related absorption variation of BC particles under ambient conditions. In particular, atmospheric measurements at fixed sites are affected by transport, local emissions, and chemistry, and quantification of the evolution in the BC properties (such as morphology, mixing state, and absorption and scattering coefficients) during aging involves complex decoupli...

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Section: Significancementioning

confidence: 99%

Markedly enhanced absorption and direct radiative forcing of black carbon under polluted urban environments

Peng

Guo

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

516

479

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“…The PI emissions are that of year 1750 as in Schulz et al (2006). According to Schulz et al (2006) and Myhre et al (2012), the anthropogenic forcing is defined as Heintzenberg et al (2000). The simulations shown in red and blue correspond to the HAM1 and HAM2 simulations, respectively.…”

Section: Direct Radiative Effect Of Aerosolsmentioning

confidence: 99%

“…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%

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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“…Recent multi-model studies 11,12 have indicated that, at recent emission levels, sulphate is the dominant anthropogenic aerosol contributor to climate forcing over black carbon or organic carbon. We also performed simulations perturbing regional black carbon emissions but, consistent with these studies, we were unable to observe any significant large-scale climate impacts for realistic emission changes, and so results for black carbon are not presented here.…”

Section: Modelling Of Regional Aerosol Emission Reductionsmentioning

confidence: 99%

Similar spatial patterns of global climate response to aerosols from different regions

2018

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Anthropogenic aerosol forcing is spatially heterogeneous, mostly localised around industrialised regions like North America, Europe, East and South Asia. Emission reductions in each of these regions will force the climate in different locations, which could have diverse impacts on regional and global climate. Here, we show that removing sulphur dioxide (SO 2 ) emissions from any of these northern-hemisphere regions in a global composition-climate model results in significant warming across the hemisphere, regardless of the emission region. Although the temperature response to these regionally localised forcings varies considerably in magnitude depending on the emission region, it shows a preferred spatial pattern independent of the location of the forcing. Using empirical orthogonal function analysis, we show that the structure of the response is tied to existing modes of internal climate variability in the model. This has implications for assessing impacts of emission reduction policies, and our understanding of how climate responds to heterogeneous forcings.

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Radiative forcing of the direct aerosol effect from AeroCom Phase II simulations

Cited by 104 publications

References 83 publications

Markedly enhanced absorption and direct radiative forcing of black carbon under polluted urban environments

Markedly enhanced absorption and direct radiative forcing of black carbon under polluted urban environments

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

Similar spatial patterns of global climate response to aerosols from different regions

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