![Scanning electron microscope image of BC aggregates in young smoke from the Madikwe Game Reserve fire, South Africa, on 20 August 2000; (b) transmission electron microscope (TEM) image of chain-like BC aggregates in flaming smoke from the dambo fire near Kaoma, Zambia, on 5 September 2000; (c) TEM image of a compact BC aggregate in regional haze near Skukuza, South Africa, on 22 August 2000 [Li et al., 2003]. (Reproduced with permission of the American Geophysical Union).](https://www.researchgate.net/profile/S-Doherty/publication/260000142/figure/fig18/AS:268044970754097@1440918309889/Scanning-electron-microscope-image-of-BC-aggregates-in-young-smoke-from-the-Madikwe-Game_Q320.jpg)
![Mass and number size distributions of BC particles observed in three fresh urban (red) and two fresh biomass burning (black) plumes as identified in the legend. The measurements are made on board an aircraft using an in situ, single-particle detection instrument (SP2). The variable coatings on the BC particles is not shown. The observed (a) mass and (b) number amounts are plotted as symbols versus volume equivalent diameter based on assuming a spherical particle shape. The mass distributions are normalized to the same peak value. The observations are fit by a lognormal function between 90 and 600 nm (solid lines). The number distribution fits are those consistent with the fit to the respective mass distribution and are scaled to represent the same BC mass. From Schwarz et al. [2008b].](https://www.researchgate.net/profile/S-Doherty/publication/260000142/figure/fig29/AS:268055200661505@1440920748367/Mass-and-number-size-distributions-of-BC-particles-observed-in-three-fresh-urban-red_Q320.jpg)
![Critical supersaturation required to activate particles of varying size and BC content into cloud condensation nuclei. Higher supersaturation values mean that particles are less likely to become cloud droplets. Results are from a particle-resolved model that simulates coagulation and condensation in ambient air onto individual particles. The two branches show aged particles from diesel exhaust (70% BC) and gasoline exhaust (20% BC), assuming that Köhler theory describes activation. Particle diameter has the greatest effect on activation, with BC content inhibiting activation to a lesser extent. Figure is based on simulations [Deville et al., 2011] of particle-resolved model [Riemer et al., 2009].](https://www.researchgate.net/profile/S-Doherty/publication/260000142/figure/fig38/AS:268058887454720@1440921627095/Critical-supersaturation-required-to-activate-particles-of-varying-size-and-BC-content_Q320.jpg)
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Bounding the role of black carbon in the climate system: A Scientific assessment
Abstract and Figures
Black carbon aerosol plays a unique and important role in Earth's climate system. Black carbon is a type of carbonaceous material with a unique combination of physical properties. This assessment provides an evaluation of black-carbon climate forcing that is comprehensive in its inclusion of all known and relevant processes and that is quantitative in providing best estimates and uncertainties of the main forcing terms: direct solar absorption; influence on liquid, mixed phase, and ice clouds; and deposition on snow and ice. These effects are calculated with climate models, but when possible, they are evaluated with both microphysical measurements and field observations. Predominant sources are combustion related, namely, fossil fuels for transportation, solid fuels for industrial and residential uses, and open burning of biomass. Total global emissions of black carbon using bottom-up inventory methods are 7500 Gg yr(-1) in the year 2000 with an uncertainty range of 2000 to 29000. However, global atmospheric absorption attributable to black carbon is too low in many models and should be increased by a factor of almost 3. After this scaling, the best estimate for the industrial-era (1750 to 2005) direct radiative forcing of atmospheric black carbon is +0.71 W m(-2) with 90% uncertainty bounds of (+0.08, +1.27) W m(-2). Total direct forcing by all black carbon sources, without subtracting the preindustrial background, is estimated as +0.88 (+0.17, +1.48) W m(-2). Direct radiative forcing alone does not capture important rapid adjustment mechanisms. A framework is described and used for quantifying climate forcings, including rapid adjustments. The best estimate of industrial-era climate forcing of black carbon through all forcing mechanisms, including clouds and cryosphere forcing, is +1.1 W m(-2) with 90% uncertainty bounds of +0.17 to +2.1 W m(-2). Thus, there is a very high probability that black carbon emissions, independent of co-emitted species, have a positive forcing and warm the climate. We estimate that black carbon, with a total climate forcing of +1.1 W m(-2), is the second most important human emission in terms of its climate forcing in the present-day atmosphere; only carbon dioxide is estimated to have a greater forcing. Sources that emit black carbon also emit other short-lived species that may either cool or warm climate. Climate forcings from co-emitted species are estimated and used in the framework described herein. When the principal effects of short-lived co-emissions, including cooling agents such as sulfur dioxide, are included in net forcing, energy-related sources (fossil fuel and biofuel) have an industrial-era climate forcing of +0.22 (-0.50 to +1.08) W m(-2) during the first year after emission. For a few of these sources, such as diesel engines and possibly residential biofuels, warming is strong enough that eliminating all short-lived emissions from these sources would reduce net climate forcing (i.e., produce cooling). When open burning emissions, which emit high levels of organic matter, are included in the total, the best estimate of net industrial-era climate forcing by all short-lived species from black-carbon-rich sources becomes slightly negative (-0.06 W m(-2) with 90% uncertainty bounds of -1.45 to +1.29 W m(-2)). The uncertainties in net climate forcing from black-carbon-rich sources are substantial, largely due to lack of knowledge about cloud interactions with both black carbon and co-emitted organic carbon. In prioritizing potential black-carbon mitigation actions, non-science factors, such as technical feasibility, costs, policy design, and implementation feasibility play important roles. The major sources of black carbon are presently in different stages with regard to the feasibility for near-term mitigation. This assessment, by evaluating the large number and complexity of the associated physical and radiative processes in black-carbon climate forcing, sets a baseline from which to improve future climate forcing estimates.
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... Large amounts of black carbon (BC) are emitted into the atmosphere from the incomplete combustion of fossil fuels and 25 biomass burning (Bond et al., 2013;Liu et al., 2020). BC is the most absorbing atmospheric aerosol and therefore affects the Earth's climate system (Bond et al., 2006;Bond and Bergstrom, 2007). ...
... BC is the most absorbing atmospheric aerosol and therefore affects the Earth's climate system (Bond et al., 2006;Bond and Bergstrom, 2007). Compared with greenhouse gases such as carbon dioxide and methane, the atmospheric lifetime of BC is relatively shorter, in the range of hours to days (Bond et al., 2013). According to the sixth Intergovernmental Panel on Climate Change (IPCC, 2021) report, BC light absorption has significant regional effects. ...
... The uncertainties of BC climate forcing estimation can be attributed to a limited understanding of its size distribution, mixing state, morphology, spatiotemporal distribution, and absorption properties, all of which require more representative and long-term measurements (Cappa et al., 2012;Bond et al., 2013;Liu et al., 2017;Romshoo et al., 2021). The size 35 distribution of BC is mainly related to different sources, e.g. ...
Uncertainties remain in estimating black carbon's (BC) radiative forcing due to a limited understanding of its microphysical properties. This study investigated the physical properties of refractory black carbon (rBC) at the central 10 European background site Melpitz during summer and winter, using a single particle soot photometer coupled with a thermodenuder. Different air masses associated with distinct rBC properties were identified in both seasons. In summer, rBC exhibited a similar mass concentration (~0.16 μg m-3) among different air masses, with the smallest mass median diameter (MMD) of rBC overserved in the long transportation from the northwest (140nm), while in winter, the highest concentration (1.23 μg m-3) and largest MMD (216 nm) were both observed in the air mass influenced by the easterly 15 winds. Thickly coated rBC fractions increased during the daytime in summer, indicating the photochemical processes significantly influence the rBC mixing state. In winter, a higher fraction (27%) of rBC with thick coating in the cold air mass compared to the warm air mass (14%) suggests the contribution of residential heating emissions to the mixing state. Most rBC retained a low-volatile coating in the thermodenuder samples (58% mass fraction). In summer, photochemical processes also contribute to coating volatility, showing a higher fraction of rBC particles containing low-volatile coatings 20 during the daytime. In winter, low-volatile coatings showed no significant diurnal variation and were more dependent on ambient temperature. Therefore, rBC coating volatility in winter is more influenced by emission sources, particularly residential heating, rather than atmospheric processes.
... Black carbon poses health hazards [69][70][71] and is also capable of altering Earth's climate via perturbations in radiative forcing [72][73][74]. It has a high GWP (global warming potential) [75], which is counterbalanced by its short persistence time in the atmosphere [76,77]. ...
The central Mediterranean and nearby regions were affected by extreme wildfires during summer 2021. During the crisis, Türkiye, Greece, Italy and other countries faced numerous challenges ranging from the near complete destruction of landscapes to human losses, and high outputs in emissions which compromised local air quality. In the Mediterranean basin, atmospheric monitoring stations perform continuous measurements of chemical and meteorological parameters meant to track and evaluate greenhouse gas and pollutant emissions in the area. In the case of wildfires, CO (carbon monoxide) and formaldehyde (HCHO) are effective tracers and the integration of satellite data on tropospheric column densities with surface measurements can provide additional insights on the transport of air masses originating from wildfires. At the Lamezia Terme (code: LMT) World Meteorological Organization – Global Atmosphere Watch (WMO/GAW) observation site in Calabria, Southern Italy, a new multiparameter approach combining different methodologies has been used to expand the knowledge the summer 2021 crisis. A previous study focused on wildfires affecting specifically the Aspromonte massif area in Calabria itself: in this study, the integration of surface concentrations, tropospheric columns, and backtrajectories has allowed to pinpoint additional contributions from other southern Italian regions, north Africa and Greece. CO data were available for both surface and column assessments, while HCHO data were only available through satellite. In order to correlate the observed peaks with wildfire phenomena, surface BC (black carbon) was also analyzed. The analysis, which focused on July and August 2021 data, pinpointed case studies highlighting distinct sources of combustion processes during the wildfire crisis of that year. Although wildfires have certain local effects in terms of biomass loss and direct damage to both the environment and human infrastructures, their broad impact on air quality also requires monitoring via the integration of multiple methodologies and the cross-analysis of satellite and surface data.
... Black carbon (BC) is a carbonaceous aerosol emitted through incomplete combustion and has a great effect on the global radiative balance and climate system (Andreae & Gelencsér, 2006;Bond et al., 2013;Ramanathan & Carmichael, 2008). It not only absorbs solar radiation directly, but also exerts indirect radiative forcing on the earth by participating in the cloud formation and depositing on the ice and snow (Flanner et al., 2007;X. ...
Plain Language Summary
Black carbon (BC) significantly affects the radiation balance of the globe due to its light‐absorbing capability. The absorption enhancement of BC Eabs is induced when BC is coated by other components. However, large discrepancies exist between observed and simulated Eabs , primarily due to the complex BC mixing state. In this study, we developed a high‐resolution sectional model that resolves both aerosol size and BC core size distributions, linking dynamic precesses with BC mixing state. Utilizing this model, we find that BC mixing state tends to become steady in a short period of time due to the balance among particle emission, growth and deposition. BC mixing state can be effectively represented by the size distribution of BC‐containing particles in the steady state, exhibiting an approximately linear relation with particle size on a logarithmic scale. Condensation of gaseous species plays an important role on the equilibrium between particle growth and deposition. The exponential size distribution in the steady state is validated across diverse atmospheric conditions.
... In particular, including ACI contributes to a warming as well as drying effect over Southern India and South Asia. For BC aerosols, which make a smaller contribution to the total aerosol number than SO 4 and have previously been shown to influence climate primarily through direct scattering and absorption of radiation (Bond et al., 2013), ACI is not yet implemented in FORTE2. This is a potential avenue for further development, in order fully represent the processes that link BC to local and remote climate effects, however it is expected to be of secondary importance. ...
Emissions of anthropogenic aerosols are rapidly changing, in amounts, composition and geographical distribution. In East and South Asia in particular, strong aerosol trends combined with high population densities imply high potential vulnerability to climate change. Improved knowledge of how near‐term climate and weather influences these changes is urgently needed, to allow for better‐informed adaptation strategies. To understand and decompose the local and remote climate impacts of regional aerosol emission changes, we perform a set of Systematic Regional Aerosol Perturbations (SyRAP) using the reduced‐complexity climate model FORTE 2.0 (FORTE2). Absorbing and scattering aerosols are perturbed separately, over East Asia and South Asia, to assess their distinct influences on climate. In this paper, we first present an updated version of FORTE2, which includes treatment of aerosol‐cloud interactions. We then document and validate the local responses over a range of parameters, showing for instance that removing emissions of absorbing aerosols over both East Asia and South Asia is projected to cause a local drying, alongside a range of more widespread effects. We find that SyRAP‐FORTE2 is able to reproduce the responses to Asian aerosol changes documented in the literature, and that it can help us decompose regional climate impacts of aerosols from the two regions. Finally, we show how SyRAP‐FORTE2 has regionally linear responses in temperature and precipitation and can be used as input to emulators and tunable simple climate models, and as a ready‐made tool for projecting the local and remote effects of near‐term changes in Asian aerosol emissions.
... It is a particulate pollutant emitted from the incomplete combustion of fossil fuels and biofuels [1], and subsequently released into the atmosphere, where it generates a significant and adverse impact on climate change. The International Maritime Organization (IMO) defines black carbon as a unique carbonaceous material with multiple physical properties [2], produced by combustion and emitted directly into the atmosphere. Black carbon is an important component of greenhouse gases and is widely found in nature. ...
Black carbon, a short-lived climate forcer, has the dual impact of intensifying global warming and polluting the atmosphere. The further opening of Arctic shipping routes has resulted in a severe issue of black carbon emissions in this fragile region. The use of fuel, especially heavy fuel oil, in international shipping has generated enormous black carbon emissions, posing a serious threat to the climate in the Arctic and beyond. As the international community continues to pay attention to air pollution control and greenhouse gas emissions reduction, the need for effective global governance of black carbon emissions from Arctic shipping has become increasingly evident. This issue has emerged as a critical part of the broader effort to address ocean and climate governance through the lens of international law. Despite the efforts made by both the International Maritime Organization (IMO) and the Arctic Council (AC) to reduce black carbon emissions, the current international legal framework remains fragmented, with weak enforcement mechanisms and limited capacity for coordinated governance. The findings of this research underscore the importance of strengthening international legal instruments aimed at reducing black carbon emissions from Arctic shipping. In particular, there is a pressing need for the development of a dedicated international treaty with enhanced binding force to mitigate the ecological degradation in the Arctic, address global warming, and realize sustainable development goals.
Polycyclic aromatic hydrocarbons (PAHs) play a major role in the chemistry of combustion, pyrolysis, and the interstellar medium. Production (or activation) of radical PAHs and propagation of their resulting reactions require efficient dehydrogenation, but the preferred method of hydrogen loss is not well understood. Unimolecular hydrogen ejection (i.e., direct C─H bond fission) and bimolecular radical abstraction are two main candidate pathways. We performed a computational study to characterize the role of H ejection, particularly as a driver for radical-centric hydrocarbon-growth mechanisms and particle formation. Electronic structure calculations establish that C─H bond strengths span a broad range of energies, which can be weaker than 30 kcal/mol in some C 9 and C 13 PAH radicals. At T > 1200 K, calculated thermal rates for hydrogen ejection from weak C─H bonds at zigzag sites on PAH radicals are significantly larger than typical H-abstraction rates. These results are highly relevant in the context of chain reactions of radical species and soot inception under fuel-rich combustion conditions. Furthermore, calculated microcanonical rates that include the additional internal energy released by bond formation (e.g., ring closure to yield C 9 H 9 ) yield significantly higher rates than those associated with full thermalization. These microcanonical considerations are relevant to the astrochemical processes associated with hydrocarbon growth and processing in the low-density interstellar environment.
Carbonaceous aerosols (CA), composed of black carbon (BC) and organic matter (OM), significantly impact the climate. Light absorption properties of CA, particularly of BC and brown carbon (BrC), are crucial due to their contribution to global and regional warming. We present the absorption properties of BC (bAbs,BC) and BrC (bAbs,BrC) inferred using Aethalometer data from 44 European sites covering different environments (traffic (TR), urban (UB), suburban (SUB), regional background (RB) and mountain (M)). Absorption coefficients showed a clear relationship with station setting decreasing as follows: TR > UB > SUB > RB > M, with exceptions. The contribution of bAbs,BrC to total absorption (bAbs), i.e. %AbsBrC, was lower at traffic sites (11-20%), exceeding 30% at some SUB and RB sites. Low AAE values were observed at TR sites, due to the dominance of internal combustion emissions, and at some remote RB/M sites, likely due to the lack of proximity to BrC sources, insufficient secondary processes generating BrC or the effect of photobleaching during transport. Higher bAbs and AAE were observed in Central/Eastern Europe compared to Western/Northern Europe, due to higher coal and biomass burning emissions in the east. Seasonal analysis showed increased bAbs, bAbs, BC, bAbs,BrC in winter, with stronger %AbsBrC, leading to higher AAE. Diel cycles of bAbs, BC peaked during morning and evening rush hours, whereas bAbs,BrC, %AbsBrC, AAE, and AAEBrC peaked at night when emissions from household activities accumulated. Decade-long trends analyses demonstrated a decrease in bAbs, due to reduction of BC emissions, while bAbs,BrC and AAE increased, suggesting a shift in CA composition, with a relative increase in BrC over BC. This study provides a unique dataset to assess the BrC effects on climate and confirms that BrC can contribute significantly to UV-VIS radiation presenting highly variable absorption properties in Europe.
This study examines the environmental and health impacts caused by the release of polycyclic aromatic hydrocarbons (PAHs) from the combustion of biomass and agricultural waste. Today, bioenergy plays a crucial role in global energy systems, accounting for 70 % of renewable energy consumption, 9.5 % of total primary energy supply, and 13 % of global gross final energy consumption. However, environmental pollution remains one of the greatest challenges of the 21st century, with serious implications for human health, biodiversity, and climate change. PAHs, released during the incomplete combustion of organic fuels, are particularly concerning due to their carcinogenic and mutagenic properties. This review aims to evaluate the emissions of PAHs during biomass combustion, with a focus on fuel types and combustion conditions. It synthesizes data from over 30 contemporary scientific sources, comprehensively analysing PAH formation and distribution in flue gases, and identifies the key factors influencing these emissions. The research reveals that PAH emissions vary significantly depending on the type of biomass, combustion conditions, and the control measures employed. Open burning of agricultural residues generates much higher PAH concentrations compared to controlled combustion in stoves or furnaces. The analysis assumes consistent data reporting across studies and acknowledges that real-world conditions may differ from laboratory settings, potentially affecting emission levels. The findings underscore the importance of implementing effective emission control strategies to reduce environmental and health risks, particularly in regions like Ukraine that rely heavily on biomass as an energy source. By addressing a critical gap in the literature, this review enhances understanding of the long-term impacts of bioenergy on environmental health and sustainability and advocates for updating Ukrainian regulatory legislation with modern methodological procedures.
This study undertakes the spatio-temporal analysis of the concentrations of criteria air pollutants—NO₂, SO₂, PM₂.₅, and CO—utilizing ground-based monitoring datasets from Delhi for the period 2021-22. The investigation meticulously assesses pollutant variability in relation to meteorological variables including wind velocity, wind direction, near-surface air temperature, planetary boundary layer (PBL) dynamics, and relative humidity. Notably, the average NO₂ concentration is observed to be marginally elevated in the post-monsoon season (45.63 ± 17.84 µg/m³), with winter concentrations closely trailing (44.53 ± 15.95 µg/m³). CO levels exhibit a pronounced peak in winter (1.56 ± 1.05 mg/m³), correlating with the agricultural residue combustion in Punjab and Haryana. The highest SO₂ concentration is recorded in summer (17.24 ± 6.59 µg/m³), likely attributed to emissions from industrial sources and thermal power stations. For PM₂.₅, winter demonstrates the highest surface concentration (148.41 ± 79.61 µg/m³), with the post-monsoon season following (133.80 ± 82.14 µg/m³). A significant novel contribution of this study lies in the application of Concentration Weighted Trajectory (CWT) and cluster analysis via backward trajectory modeling of air parcels at an elevation of 100 m above ground level (AGL) using the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model. This methodology, applied across the Winter (DJF), Summer (MAM), Monsoon (JJAS), and Post-monsoon (ON) seasons, unveils critical insights into the spatio-temporal patterns and emission source regions for these pollutants. The trajectories reveal that major pollutant transport pathways are predominantly WNW, NW, and NNW. Trans-boundary long-range transport from NW is identified as a significant factor, while regional contributions from Punjab and Haryana are substantial. The study identifies that the winter season is primarily responsible for the highest pollutant concentrations across all pollutants, except SO₂, which exhibits its peak contributing area during the summer season.
Black carbon, or soot, significantly contributes to atmospheric light absorption due to its low single scattering albedo (SSA). This study investigates the impact of soot's hygroscopic restructuring on satellite remote sensing, focusing on radiative forcing, top-of-atmosphere (TOA) reflectance, and aerosol optical depth (AOD) retrievals. We characterized soot aging using relative humidity (RH) growth factor functions and modeled fresh and aging soot aggregates using a cluster-cluster aggregation algorithm. Bulk optical properties for each RH level were simulated using core-mantle generalized multi-sphere Mie-solution, weighted by the probability density function of soot monomer numbers. We incorporated soot aging models into the 6S radiative transfer model by adjusting the geometric mean radius of the soot component to match bulk SSA values at each aging degree. Extensive radiative transfer simulations were conducted, complemented by an analysis of 16 actual soot-containing cases in China from 2016 to 2019. Results showed that identical soot loads correspond to lower reflectance in dry environments and higher reflectance in humid environments. MODIS AOD retrieval errors approached zero when RH was close to 70 %, likely due to the similarity between the 6S default soot and the aging model at this humidity. Neglecting RH led to overestimations in AOD for cases with RH < 65 % and underestimations in high humidity cases (RH > 75 %). The average MODIS AOD retrieval errors for RH < 65 %, RH between 65 % and 75 %, and RH > 75 % were −33.15 %, −1.80 %, and +42.42 %, respectively. This study underscores the necessity of incorporating RH into satellite AOD retrieval algorithms to enhance accuracy and reduce uncertainties.
211 estimates of the social cost of carbon are included in a meta-analysis. The results confirm that a lower discount rate implies a higher estimate; and that higher estimates are found in the gray literature. It is also found that there is a downward trend in the economic impact estimates of the climate; that the Stern Review’s estimates of the social cost of carbon is an outlier; and that the right tail of the distribution is fat. There is a fair chance that the annual climate liability exceeds the annual income of many people.
An assessment is made of each component of the heat budgets of the surface and of the earth-atmosphere system in the central Arctic, both for an ice-covered ocean and for an ice-free ocean. The annual patterns of atmospheric heat loss for both conditions are obtained as residuals; the relation of these patterns to general atmospheric circulation and glacier accumulation is discussed.
It is shown that atmospheric cooling in the Arctic is closely related to certain indices of atmospheric circulation. An ice-free Arctic Ocean would probably be associated with atmospheric circulation more vigorous in summer at subarctic latitudes and of comparable vigor in winter. The cool summers and warm, moist winters would be highly conducive to glacier growth.
Particulate elemental carbon is found in the atmosphere in both urban and remote regions and isoften responsible for much of the absorption of solar radiation by atmospheric aerosols. Itsatmospheric lifetime is controlled by four factors: the initial size distribution, the concentrationof ambient particles, the frequency and duration of precipitation, and the efficiencies of removalmechanisms. A model of the atmospheric cycle of particulate elemental carbon which includesthese factors has been used to estimate the range of atmospheric lifetimes expected under variousconditions. Calculated lifetimes range from under 40 hours in rainy climates to well over 1 weekin clean, dry regions. DOI: 10.1111/j.1600-0889.1983.tb00027.x
