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Warming influenced by the ratio of black carbon to sulphate and the black-carbon source
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Black carbon is generated by fossil-fuel combustion and biomass burning. Black-carbon aerosols absorb solar radiation, and are probably a major source of global warming. However, the extent of black-carbon-induced warming is dependent on the concentration of sulphate and organic aerosols-which reflect solar radiation and cool the surface-and the origin of the black carbon. Here we examined the impact of black-carbon-to-sulphate ratios on net warming in China, using surface and aircraft measurements of aerosol plumes from Beijing, Shanghai and the Yellow Sea. The Beijing plumes had the highest ratio of black carbon to sulphate, and exerted a strong positive influence on the net warming. Compiling all the data, we show that solar-absorption efficiency was positively correlated with the ratio of black carbon to sulphate. Furthermore, we show that fossil-fuel-dominated black-carbon plumes were approximately 100% more efficient warming agents than biomass-burning-dominated plumes. We suggest that climate-change-mitigation policies should aim at reducing fossil-fuel black-carbon emissions, together with the atmospheric ratio of black carbon to sulphate.
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... The observed larger spread in ATM and a simultaneous less cooling TOA is consistent with the joint effects of changes in BC aging and BC size on the per-particle optical properties, with modeling studies done by Wu et al. 66 demonstrating that BC could obtain a positive regional TOA after significant aging, Cohen et al. 12 demonstrating a global increase in TOA as a function of the change in the size of aged BC, and Ramana et al. 67 showing that a critical ratio of BC to sulfate can yield a positive TOA. Supplementary Fig. 1 shows the PDF of surface spectral albedo, BC sizes, and size ratio solutions at the two sites, indicating that the two sites have significant differences in these aspects. ...
... Statistical metrics of TOA and ATM under different BC core sizes and AOD conditions are presented in Table 2 and visualized for small and extremely big core sizes under clean and polluted conditions in Fig. 2. First, irrespective of the core size, AOD condition, or site, COSMO-TOA always has a less negative value than AERONET-TOA, including both when varying core size at constant AOD, as well as when varying AOD at constant core size. COSMO-TOA becomes negative more slowly for each and every fixed AOD condition as the BC size increases (aerosols are less cooling) at both Lumbini and Taihu, similar to findings by 67,78 . However, the rate of change is slower at Lumbini across all AOD conditions as the core size increases than in Taihu. ...
Direct radiative forcing (DRF) of aerosols is driven by aerosol concentration, size, and mixing state, and solar radiation. This work introduces Core-Shell Mie model optimization (COSMO) to compute top of the atmosphere (TOA) forcing based on inversely constrained black carbon (BC) size and mixing state from AERONET, over two rapidly developing areas: Lumbini and Taihu. COSMO has both, a less negative TOA than AERONET and a wider range of variability, with the mean and standard deviation difference between COSMO and AERONET being 13 ± 8.1 W m−2 at Lumbini and 16 ± 12 W m−2 at Taihu. These differences are driven by particle aging and size-resolved BC emissions, with up to 17.9% of cases warmer than the maximum AERONET TOA, and 1.9% of the total possible cases show a net-warming at TOA (TOA > 0). A linearized correction is deduced which can be immediately implemented by climate models, and suggested ranges of BC size and mixing observations are made for future campaigns. Given that the COSMO TOA bias and uncertainty are larger than the forcing of locally emitted GHGs, active consideration of BC is necessary to reduce climate uncertainty in developing areas.
... This is due to its ability to absorb incoming solar radiation, leading to temperature rises on ice surfaces or in the atmosphere (Rajesh and Ramachandran 2022). Hence, such anthropogenic activities are proven sources of BC emission in the atmosphere (Ramana et al. 2010) and potential causes of global warming (Resquin et al. 2018). However, its extinction is dependent on the scattering ability of sulfate particles and the emission potential of the responsible sources of BC . ...
An extinction of incoming solar radiation is taking place by absorption and scattering by dust, water droplets, and gaseous molecules. Such phenomena are responsible for altering meteorological variables. In the present study, temporal analysis of the aerosol optical thickness (AOT) and black carbon (BC) surface mass concentration was undertaken using an ozone monitoring instrument (OMI) and modern-era retrospective analysis for research and applications, version 2 (MERRA-2) satellite from the year 2018 to 2022. The study was mainly focused on the western states of India which are Rajasthan, Gujarat, and Maharashtra. The correlation of AOT and BC surface mass concentration with near-surface temperature (2m above ground level) was analyzed. BC and temperature shows strong negative correlation as BC is known for its absorption of radiation. It accumulates in the atmosphere and contributes to atmospheric warming while simultaneously bringing down the near-surface air temperature due to the reduced sunlight reaching the ground. Also, seasonal analysis was conducted for winter, summer, monsoon, and post-monsoon, which shows the higher values of AOT in monsoon; however, seasonal average BC surface mass concentration was found high in winter in each year for all three states. AERONET data from Jaipur, Rajasthan, and Pune, Maharashtra for the year 2021 was used to further evaluate the AOT generated from OMI. The results demonstrated a significant connection, with R² values of 0.62 and 0.69, respectively. The temperature retrieved from MERRA-2 was also validated with ground truth data of the Continuous Ambient Air Quality Monitoring Station (CAAQMS) at both stations showing high agreement with R² > 0.70.
... The current study focuses on regionally relevant E MAC and has several references. For instance, Ramana et al. (2010) noted that BC MAC observed at receptor sites in E Asia was higher than in S Asia, and suggested a link to higher SO₄ 2− /EC as an indication of coatings in the former system as an explanation. Peng et al. (2016) performed long-term chamber studies with ambient polluted air in Beijing and demonstrated a large E MAC-BC (> 2) after several days of aging of such polluted air. ...
... According to the sixth IPCC report, the total direct radiative forcing caused by anthropogenic aerosols is generally negative. However, light-absorbing carbonaceous (LAC) particles have a warming effect on climate (Ramana et al., 2010;Gustafsson and Ramanathan, 2016), which can partly offset the cooling effect caused by scattering aerosols, such as sulfate. Black carbon (BC) is the most important LAC compound. ...
In this study, the mixing state of size-resolved soot particles and their influencing factors were investigated based on a 5-month aerosol volatility measurement at a suburban site (Xingtai, XT) in the central North China Plain (NCP). The volatility and mixing state of soot-containing particles at XT were complex, caused by multiple pollution sources and various aging processes. The results suggest that anthropogenic emissions can weaken the mean volatility of soot-containing particles and enhance their degree of external mixing. There were fewer externally mixed soot particles in warm months (June, July, and August) than in cold months (May, September, and October). Monthly variations in the mean coating depth (Dc,mean) of volatile matter on soot particles showed that the coating effect was stronger in warm months than in cold months, even though aerosol pollution was heavier in cold months. Moreover, the volatility was stronger, and the degree of internal mixing was higher in nucleation-mode soot-containing particles than in accumulation-mode soot-containing particles. Relationships between Dc,mean and possible influencing factors (temperature (T), relative humidity (RH), and particulate matter, with diameters ranging from 10 to 400 nm) further suggest that high ambient T and RH in a polluted environment could promote the coating growth of accumulation-mode soot particles. However, high ambient T but low RH in a clean environment was beneficial to the coating growth of nucleation-mode soot particles. Our results highlight the diverse impact of anthropogenic emissions and aging processes on the mixing state of soot particles in different modes, which should be considered separately in models to improve the simulation accuracy of aerosol absorption.
... The red and blue stars represent the weekdays and weekends, respectively. The dashed red, blue, and black solid lines show the linear fit for the weekdays, weekends, and complete dataset BC emissions enhance atmospheric warming, as the fossil-fuel-dominated black-carbon plumes are known to be more efficient warming agents (Jacobson 2001; Ramana et al. 2010). The warming of the atmosphere can be observed with the help of changes in the air temperature corresponding to climate change. ...
Mineral dust, originating in arid regions, exerts substantial influence on air quality, health, and climate, ranking it among the most impactful aerosols. Its capacity to travel over great distances can significantly impact local air quality. In our study conducted for the year 2021, we made use of unprecedented, simultaneous in situ measurements to assess the total number, mass concentrations, and size distribution of near-surface aerosols at a semi-arid station. Furthermore, we conducted an in-depth examination of dust episodes, drawing upon evidence from in situ measurements of surface aerosol properties and meteorological records. The highest total number concentrations (230.1 ± 60.61 cm⁻³) were recorded during the winter season, attributed to a combination of factors including low temperatures, high relative humidity, stable wind conditions, and limited dispersion. Our findings reveal a noteworthy correlation: for every 1% increase in the equivalent black carbon mass fraction, the diurnal temperature range rises by 1.73 °C, with a noticeable impact of the weekend effect. During the dust episodes occurring on April 7–10 and June 16–30, we observed a significant increase (> twofold) in various surface parameters, such as number size distribution (NSD), total and coarse mode mass concentrations, effective radius, and scattering coefficient. Particularly striking was the enhancement in NSD during these dust episodes, consistently exceeding twofold for aerosols larger than 1.0 µm and reaching as high as tenfold for aerosols larger than 5.0 µm. In addition to our surface observations, satellite vertical profiles showed a prominent dust elevated layer situated between 2 and 4 km altitude during the dust episodes. These observations were well-aligned with in situ surface data and dust columnar mass flux obtained from re-analysis data. Re-analysis and model data further support our findings, indicating a long-range transport of aerosols from the Middle East and South Asia during the dust episodes.
Aerosol- and moonsoon-related droughts and floods are two of the most serious environmental hazards confronting more than 60% of the population of the world living in the Asian monsoon countries. In recent years, thanks to improved satellite and in situ observations, and better models, great strides have been made in aerosol and monsoon research, respectively. There is now a growing body of evidence suggesting that interaction of aerosol forcing with monsoon dynamics may alter the redistribution of energy in the atmosphere and at the Earth's surface, thereby influencing monsoon water cycle and climate. In this article, the authors describe the scientific rationale and challenges for an integrated approach to study the interactions between aerosol and monsoon water cycle dynamics. A Joint Aerosol-Monsoon Experiment (JAMEX) is proposed for 2007-11, with enhanced observations of the physical and chemical properties, sources and sinks, and long-range transport of aerosols, in conjunction with meteorological and oceanographic observations in the Indo-Pacific continental and oceanic regions. JAMEX will leverage on coordination among many ongoing and planned national research programs on aerosols and monsoons in China, India, Japan, Nepal, Italy, and the United States, as well as international research programs of the World Climate Research Program (WCRP) and the World Meteorological Organization (WMO).
Understanding the roles of human and natural sources in contributing to aerosol concentrations around the world is an important step toward developing efficient and effective mitigation measures for local and regional air quality degradation and climate change. In this study we test the hypothesis that changes in aerosol optical depth (AOD) over time are caused by the changing patterns of anthropogenic emissions of aerosols and aerosol precursors. We present estimated trends of contributions to AOD for eight world regions from 1980 to 2006, built upon a full run of the Goddard Chemistry Aerosol Radiation and Transport model for the year 2001, extended in time using trends in emissions of man-made and natural sources. Estimated AOD trends agree well (R > 0.5) with observed trends in surface solar radiation in Russia, the United States, south Asia, southern Africa, and East Asia (before 1992) but less well for Organization for Economic Co-operative Development (OECD) Europe (R < 0.5). The trends do not agree well for southeast Asia and for East Asia (after 1992) where large-scale inter- and intraannual variations in emissions from forest fires, volcanic eruptions, and dust storms confound our approach. Natural contributions to AOD, including forest and grassland fires, show no significant long-term trends (
Biomass burning releases gases (e.g.,CO 2 , CO, CH 4 , NO x , SO 2 , C 2 H 6 , C 2 H 4 , C 3 H 8 , C 3 H 6 ) and aerosol-particle components (e.g., black carbon, organic matter, K + , Na + , Ca 2+ , Mg 2+ , NH 4 + , H + , Cl - , H 2 SO 4 , HSO 4 - , SO 4 2- , NO 3 - ). To date, the global-scale climate response of controlling emission of these constituents together has not been examined. Here 10-year global simulations of the climate response of biomass-burning aerosols and short-lived gases are coupled with numerical calculations of the long-term effect of controlling biomass-burning CO 2 and CH 4 to estimate the net effect of controlling burning over 100 years. Whereas eliminating biomass-burning particles is calculated to warm temperatures in the short term, this warming may be more than offset after several decades by cooling due to eliminating long-lived CO 2 , particularly from permanent deforestation. It is also shown analytically that biomass burning always results in CO 2 accumulation, even when regrowth fluxes equal emission fluxes and in the presence of fertilization. Further, because burning grassland and cropland yearly, as opposed to every several years, increases CO 2 , biofuel burning, considered a "renewable" energy source, is only partially renewable, and biomass burning elevates CO 2 until it is stopped. Because CO 2 from biomass burning is considered recyclable and biomass particles are thought to cool climate, the Kyoto Protocol did not consider biomass-burning controls. If the results here, which apply to a range of scenarios but are subject to uncertainty, are correct, such
'Soot' or 'black carbon', which comes from incomplete combustion, absorbs light and warms the atmosphere. Although there have been repeated suggestions that reduction of black carbon could be a viable part of decreasing global warming, it has not yet been considered when choosing actions to reduce climatic impact. In this paper, I examine four conceptual barriers to the consideration of aerosols in global agreements. I conclude that some of the major objections to considering aerosols under hemispheric or global agreements are illusory because: (1) a few major sources will be addressed by local regulations, but the remainder may not be addressed by traditional air quality management; (2) climate forcing by carbon particles is not limited to 'hot spots'—about 90% of it occurs at relatively low concentrations; (3) while aerosol science is complex, the most salient characteristics of aerosol behavior can be condensed into tractable metrics including, but not limited to, the global warming potential; (4) despite scientific uncertainties, reducing all aerosols from major sources of black carbon will reduce direct climate warming with a very high probability. This change in climate forcing accounts for at least 25% of the accompanying CO2 forcing with significant probability (25% for modern diesel engines, 90% for superemitting diesels, and 55% for cooking with biofuels). Thus, this fraction of radiative forcing should not be ignored.
Biomass burning is the burning of evergreen forests, deciduous forests, woodlands, grassland, and agricultural land, either to clear land for other use, to stimulate grass growth, for forest management, or as a ritual. Biomass burning releases both gases (e.g.,CO2, CO, CH4, NOx, SO2, C2H6, C2H4, C3H8, C3H6) and aerosol particle components (e.g., black carbon, organic matter, K+, Na+, Ca2+, Mg2+, NH4+, H+, Cl-, H2SO4, HSO4-, SO42-, NO3-). The global-scale climate response of controlling emissions of these gas plus particle constituents during biomass burning has not been examined to date. Whereas biomass-burning particles enhance global cooling in the short term, it is found that this cooling is partially suppressed by black carbon and more than offset in the long term by the warming effect of long-lived biomass-burning gases. The emissions of the most important of these gases, CO2, is only partially offset by biomass regrowth each year. As such, a reduction in biomass burning, not considered under the Kyoto Protocol, should slow global warming, contrary to common perception. Control of biomass-burning should also improve human health.
Historical changes of black carbon (BC) and particulate organic matter (POM) emissions from biomass burning (BB) and fossil fuel (FF) burning are estimated from 1870 to 2000. A bottom-up inventory for open vegetation (OV) burning is scaled by a top-down estimate for the year 2000. Monthly and interannual variations are derived over the time period from 1979 to 2000 based on the TOMS satellite aerosol index (AI) and this global map. Prior to 1979, emissions are scaled to a CH4 emissions inventory based on land-use change. Biofuel (BF) emissions from a recent inventory for developing countries are scaled forward and backward in time using population statistics and crop production statistics. In developed countries, wood consumption data together with emission factors for cooking and heating practices are used for biofuel estimates. For fossil fuel use, we use fuel consumption data and specific emission factors for different fuel use categories to develop an inventory over 1950–2000, and emissions are scaled to a CO2 inventory prior to that time. Technology changes for emissions from the diesel transport sector are included. During the last decade of this time period, the BC and POM emissions from biomass burning (i.e., OV + BF) contribute a significant amount to the primary sources of BC and POM and are larger than those from FF. Thus 59% of the NH BC emissions and 90% of the NH POM emissions are from BB in 2000. Fossil fuel consumption technologies are needed prior to 1990 in order to improve estimates of fossil fuel emissions during the twentieth century. These results suggest that the aerosol emissions from biomass burning need to be represented realistically in climate change assessments. The estimated emissions are available on a 1° × 1° grid for global climate modeling studies of climate changes.
A global, self-consistent estimate of sulfur dioxide emissions over the last one and a half century were estimated by using a combination of bottom-up and best available inventory methods including all anthropogenic sources. We find that global sulfur dioxide emissions peaked about 1980 and have generally declined since this time. Emissions were extrapolated to a 1{sup o} x 1{sup o} grid for the time period 1850-2000 at annual resolution with two emission height levels and by season. Emissions are somewhat higher in the recent past in this new work as compared with some comprehensive estimates. This difference is largely due to our use of emissions factors that vary with time to account for sulfur removals from fossil fuels and industrial smelting processes.