Estimation of global black carbon direct radiative forcing and its uncertainty constrained by observations

Wang, Rong; Balkanski, Yves; Boucher, Oliviér; Ciais, Philippe; Schuster, Gregory L.; Chevallier, F.; Samset, B. H.; Liu, Junfeng; Piao, Shilong; Valari, Myrto; Tao, Shu

doi:10.1002/2015jd024326

Cited by 88 publications

(72 citation statements)

References 106 publications

(245 reference statements)

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“…36) may indicate our SOA estimates are lower bounds. Our methods also use global estimates of aerosol semi-and indirect climate impacts (37) and assume a central BC radiative forcing from Bond et al (38) that has been suggested to be 27% too large (39). Our adjoint sensitivities were calculated using a single year of meteorology (2009) that may not reflect a climatological mean, although error bounds of our radiative forcing estimates do draw from comparisons of multiyear modeling studies.…”

Section: Discussionmentioning

confidence: 99%

Transient climate and ambient health impacts due to national solid fuel cookstove emissions

Henze

Lee

et al. 2017

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

115

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Residential solid fuel use contributes to degraded indoor and ambient air quality and may affect global surface temperature. However, the potential for national-scale cookstove intervention programs to mitigate the latter issues is not yet well known, owing to the spatial heterogeneity of aerosol emissions and impacts, along with coemitted species. Here we use a combination of atmospheric modeling, remote sensing, and adjoint sensitivity analysis to individually evaluate consequences of a 20-y linear phase-out of cookstove emissions in each country with greater than 5% of the population using solid fuel for cooking. Emissions reductions in China, India, and Ethiopia contribute to the largest global surface temperature change in 2050 [combined impact of −37 mK (11 mK to −85 mK)], whereas interventions in countries less commonly targeted for cookstove mitigation such as Azerbaijan, Ukraine, and Kazakhstan have the largest per cookstove climate benefits. Abatement in China, India, and Bangladesh contributes to the largest reduction of premature deaths from ambient air pollution, preventing 198,000 (102,000-204,000) of the 260,000 (137,000-268,000) global annual avoided deaths in 2050, whereas again emissions in Ukraine and Azerbaijan have the largest per cookstove impacts, along with Romania. Global cookstove emissions abatement results in an average surface temperature cooling of −77 mK (20 mK to −278 mK) in 2050, which increases to −118 mK (−11 mK to −335 mK) by 2100 due to delayed CO 2 response. Health impacts owing to changes in ambient particulate matter with an aerodynamic diameter of 2.5 µm or less (PM 2.5 ) amount to ∼22.5 million premature deaths prevented between 2000 and 2100.aerosols | climate | human health | cookstoves | atmospheric modeling G lobally over 3 billion people presently use solid fuel for meal preparation (1). The extent of this activity and the associated air quality pollutant emissions have led to numerous cookstove intervention studies and programs, such as the Global Alliance for Clean Cookstoves work to implement 60 million clean cookstoves by 2017 (cleancookstoves.org/about/news/11-20-2014-market-enabling-roadmap-phase-2-2015-2017.html). A primary goal of these efforts is to improve indoor air quality, estimated to cause ∼4.3 million premature deaths annually, along with enhancing livelihood of woman and children via reprieval from fuel collection and other solid fuel cookingrelated tasks (2).The magnitude of the emissions of aerosols, aerosol precursors, and greenhouse gases from solid fuel use has also motivated studies of the impact of these emissions on climate and ambient air quality. An estimated 370,000-500,000 global premature deaths in adults occur annually owing to ambient exposure to fine particulate matter associated with residential cookstoves (3-5), and there are as many as 1.0 million global annual premature deaths of adults and children under the age of 5 y from combined residential and commercial energy generation (which includes solid fuel use for cooking) (6). Thi...

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Section: Discussionmentioning

confidence: 99%

Transient climate and ambient health impacts due to national solid fuel cookstove emissions

Henze

Lee

et al. 2017

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

115

View full text Add to dashboard Cite

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“…One estimate puts top-of-the-atmosphere direct forcing by BC as high as 0.9 W m −2 , which is comparable in magnitude to that of CO 2 (Ramanathan and Carmichael, 2008). Other more recent assessments yield 0.71 W m −2 with 90 % uncertainty bounds of 0.08 to 1.27 W m −2 (Bond et al, 2013) (Wang et al, 2016), while the IPCC suggests a value of 0.40 [+0.05 to +0.80] W m −2 (Boucher et al, 2013).…”

Section: Introductionmentioning

confidence: 89%

Measurement and modeling of the multiwavelength optical properties of uncoated flame-generated soot

et al. 2018

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Abstract. Optical properties of flame-generated black carbon (BC) containing soot particles were quantified at multiple wavelengths for particles produced using two different flames: a methane diffusion flame and an ethylene premixed flame. Measurements were made for (i) nascent soot particles, (ii) thermally denuded nascent particles, and (iii) particles that were coated and then thermally denuded, leading to the collapse of the initially lacy, fractal-like morphology. The measured mass absorption coefficients (MACs) depended on soot maturity and generation but were similar between flames for similar conditions. For mature soot, here corresponding to particles with volume-equivalent diameters >∼ 160 nm, the MAC and absorption Ångström exponent (AAE) values were independent of particle collapse while the single-scatter albedo increased. The MAC values for these larger particles were also size-independent. The mean MAC value at 532 nm for larger particles was 9.1 ± 1.1 m 2 g −1 , about 17 % higher than that recommended by Bond and Bergstrom (2006), and the AAE was close to unity. Effective, theory-specific complex refractive index (RI) values are derived from the observations with two widely used methods: Lorenz-Mie theory and the Rayleigh-Debye-Gans (RDG) approximation. Mie theory systematically underpredicts the observed absorption cross sections at all wavelengths for larger particles (with x > 0.9) independent of the complex RI used, while RDG provides good agreement. (The dimensionless size parameter x = π d p /λ, where d p is particle diameter and λ is wavelength.) Importantly, this implies that the use of Mie theory within air quality and climate models, as is common, likely leads to underpredictions in the absorption by BC, with the extent of underprediction depending on the assumed BC size distribution and complex RI used. We suggest that it is more appropriate to assume a constant, size-independent (but wavelength-specific) MAC to represent absorption by uncoated BC particles within models.

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“…The discrepancies reported here between in situ and AERONET values of AAOD and SSA suggest that caution should be used in upscaling model results to match AERONET retrievals of absorbing aerosol as this will have a significant impact on global radiative forcing estimates. The work of Wang et al (2016) has shown that other factors (e.g., the spatial resolution of models and emissions) may also contribute to the differences observed between model and AERONET retrievals of AAOD. Thus, really being able to understand and simulate the influence of absorbing aerosol on radiative forcing will require expanded effort on both the measurement and modeling fronts.…”

Section: Discussionmentioning

confidence: 99%

“…Finally, we look at the seasonality of in situ, AERONET and modeled (AeroCom) SSA and AAOD values to see if the annual cycles can provide any insight into observed discrepancies in the direct comparisons. Because this study focuses on only two low-AOD sites in the continental US that are unlikely to be generally representative of other low-loading sites around the globe, and because other factors (e.g., Wang et al, 2016) may contribute to reported differences between modeled and AERONET AAOD, we do not attempt to suggest implications for global BC forcing.…”

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confidence: 99%

“…Alternatively, the column properties retrieved from AERONET measurements and inversions have been widely used to provide a first constraint on modeled vertical aerosol properties (e.g., Sato et al, 2003;Koch et al, 2009;Bond et al, 2013;He et al, 2014;Wang et al, 2014). Use of the AERONET data as an absorption constraint has suggested upscaling of modeled aerosol absorption optical depth (AAOD) values by a factor of 2-6 depending on location (e.g., Bond et al, 2013), although Wang et al (2016) showed that better spatial resolution of models and emission inventories can reduce some of the previously observed model-AERONET discrepancies.…”

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confidence: 99%

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Comparison of AOD, AAOD and column single scattering albedo from AERONET retrievals and in situ profiling measurements

et al. 2017

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Abstract. Here we present new results comparing aerosol optical depth (AOD), aerosol absorption optical depth (AAOD) and column single scattering albedo (SSA) obtained from in situ vertical profile measurements with AERONET ground-based remote sensing from two rural, continental sites in the US. The profiles are closely matched in time (within ±3 h) and space (within 15 km) with the AERONET retrievals. We have used Level 1.5 inversion retrievals when there was a valid Level 2 almucantar retrieval in order to be able to compare AAOD and column SSA below AERONET's recommended loading constraint (AOD > 0.4 at 440 nm). While there is reasonable agreement for the AOD comparisons, the direct comparisons of in situderived to AERONET-retrieved AAOD (or SSA) reveal that AERONET retrievals yield higher aerosol absorption than obtained from the in situ profiles for the low aerosol optical depth conditions prevalent at the two study sites. However, it should be noted that the majority of SSA comparisons for AOD 440 > 0.2 are, nonetheless, within the reported SSA uncertainty bounds. The observation that, relative to in situ measurements, AERONET inversions exhibit increased absorption potential at low AOD values is generally consistent with other published AERONET-in situ comparisons across a range of locations, atmospheric conditions and AOD values. This systematic difference in the comparisons suggests a bias in one or both of the methods, but we cannot assess whether the AERONET retrievals are biased towards high absorption or the in situ measurements are biased low. Based on the discrepancy between the AERONET and in situ values, we conclude that scaling modeled black carbon concentrations upwards to match AERONET retrievals of AAOD should be approached with caution as it may lead to aerosol absorption overestimates in regions of low AOD. Both AERONET retrievals and in situ measurements suggest there is a systematic relationship between SSA and aerosol amount (AOD or aerosol light scattering) -specifically that SSA decreases at lower aerosol loading. This implies that the fairly common assumption that AERONET SSA values retrieved at high-AOD conditions can be used to obtain AAOD at low-AOD conditions may not be valid.

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Estimation of global black carbon direct radiative forcing and its uncertainty constrained by observations

Cited by 88 publications

References 106 publications

Transient climate and ambient health impacts due to national solid fuel cookstove emissions

Transient climate and ambient health impacts due to national solid fuel cookstove emissions

Measurement and modeling of the multiwavelength optical properties of uncoated flame-generated soot

Comparison of AOD, AAOD and column single scattering albedo from AERONET retrievals and in situ profiling measurements

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