Pollutant emissions in China have significantly decreased over the past decade and are expected to continue declining in the future. Aerosols, as important pollutants and short-lived climate forcing agents, have significant but currently unclear climate impacts in East Asia as their concentrations decrease until mid-century. Here, we employ a well-developed regional climate model RegCM4 combined with future pollutant emission inventories, which are more representative of China to investigate changes in the concentrations and climate effects of major anthropogenic aerosols in East Asia under six different emission reduction scenarios (1.5 degrees C goals, Neutral-goals, 2 degrees C -goals, NDC-goals, Current-goals, and Baseline). By the 2060s, aerosol surface concentrations under these scenarios are projected to decrease by 89%, 87%, 84%, 73%, 65%, and 21%, respectively, compared with those in 2010-2020. Aerosol climate effect changes are associated with its loadings but not in a linear manner. The average effective radiative forcing at the surface in East Asia induced by aerosol-radiation-cloud interactions will diminish by 24% +/- 13% by the 2030s and 35% +/- 13% by the 2060s. These alternations caused by aerosol reductions lead to increases in near-surface temperatures and precipitations. Specifically, aerosol-induced temperature and precipitation responses in East Asia are estimated to change by -78% to -20% and -69% to 77%, respectively, under goals with different emission scenarios in the 2060s compared to 2010-2020. Therefore, the significant climate effects resulting from substantial reductions in anthropogenic aerosols need to be fully considered in the pathway toward carbon neutrality.

The light absorption enhancement (E-abs) of black carbon (BC) coated with non-BC materials is crucial in the assessment of radiative forcing, yet its evolution during photochemical aging of plumes from biomass burning, the globe's largest source of BC, remains poorly understood. In this study, plumes from open burning of corn straw were introduced into a smog chamber to explore the evolution of E-abs during photochemical aging. The light absorption of BC was measured with and without coating materials by using a thermodenuder, while the size distributions of aerosols and composition of BC coating materials were also monitored. E-abs was found to increase initially, and then decrease with an overall downward trend. The lensing effect dominated in E-abs at 520 nm, with an estimated contribution percentages of 47.5%-94.5%, which is far greater than light absorption of coated brown carbon (BrC). The effects of thickening and chemical composition changes of the coating materials on E-abs were evaluated through comparing measured E-abs with that calculated by the Mie theory. After OH exposure of 1 x 10(10) molecules cm(-3) s, the thickening of coating materials led to an E-abs increase by 3.2% +/- 1.6%, while the chemical composition changes or photobleaching induced an E-abs decrease by 4.7% +/- 0.6%. Simple forcing estimates indicate that coated BC aerosols exhibit warming effects that were reduced after aging. The oxidation of light-absorbing CxHy compounds, such as polycyclic aromatic hydrocarbons (PAHs), to CxHyO and CxHyO>1 compounds in coating materials may be responsible for the photobleaching of coated BrC. Plain Language Summary Understanding how black carbon (BC) coated with non-BC materials affects light absorption is crucial for assessing its impact on the Earth's climate. However, there is limited knowledge about how this process changes when BC, particularly from biomass burning, is exposed to light. Biomass burning is a significant global source of BC. This study investigated the changes in light absorption of BC from burning corn straw as it aged in a controlled environment. We measured the light absorption of BC with and without its coating materials. Our results showed that the main cause of increased light absorption was the lensing effect of the coating materials, which was more significant than the light absorption by the coating materials themselves. We also discovered that as the coating materials thickened, BC absorbed more light. However, changes in the chemical composition of the coating materials led to a decrease in total absorption. These findings suggest that while coated BC initially has a warming effect on the climate, this effect diminished as the BC ages. The decrease is likely due to the breakdown of light-absorbing compounds in the coating materials, such as polycyclic aromatic hydrocarbons (PAHs).

In the context of China's dual carbon goal, emissions of air pollutants are expected to significantly decrease in the future. Thus, the direct climate effects of black carbon (BC) aerosols in East Asia are investigated under this goal using an updated regional climate and chemistry model. The simulated annual average BC concentration over East Asia is approximately 1.29 mu g/m(3) in the last decade. Compared to those in 2010-2020, both the BC column burden and instantaneous direct radiative forcing in East Asia decrease by more than 55% and 80%, respectively, in the carbon peak year (2030s) and the carbon neutrality year (2060s). Conversely, the BC effective radiative forcing (ERF) and regional climate responses to BC exhibit substantial nonlinearity to emission reduction, possibly resulting from different adjustments of thermal-dynamic fields and clouds from BC-radiation interactions. The regional mean BC ERF at the tropopause over East Asia is approximately +1.11 W/m(2) in 2010-2020 while negative in the 2060s. BC-radiation interactions in the present-day impose a significant annual mean cooling of -0.2 to -0.5 K in central China but warming +0.3 K in the Tibetan Plateau. As China's BC emissions decline, surface temperature responses show a mixed picture compared to 2010-2020, with more cooling in eastern China and Tibet of -0.2 to -0.3 K in the 2030s, but more warming in central China of approximately +0.3 K by the 2060s. The Indian BC might play a more important role in East Asian climate with reduction of BC emissions in China.

The Tibetan Plateau, referred as the last pure land on the earth, is frequently exposure to heavy air pollution during springtime. Here, we find South Asia biomass burning is crucial to cause the heavy springtime air pollution over the Tibetan Plateau, which explain the most (more than 60%) of aerosol components in the region, although its contribution to gaseous pollutants is not significant. South Asian biomass burning mainly affects primary PM2.5 components black carbon (65.3%) and organic carbon (79.5%) over the Tibetan Plateau, but has little influence (less than 5%) on second aerosol components (sulfate, nitrate, and ammonium). The transboundary transmissions of aerosols were regulated by a combination of large-scale westerly winds and regional mountain-valley winds in springtime. In addition to worsen air quality, aerosols from South Asian biomass burning lead to surface temperature decrease of 0.06 degrees C, and precipitation reduction of 3.9 mm over the Tibetan Plateau during springtime. These climate changes will threat the fragile ecosystem over the Tibetan Plateau, such as plant growth and flowering during springtime. Overall, our findings demonstrate a necessary and urgency to reduce biomass burning emissions over South Asia to protect the Tibetan Plateau environment.

Brown carbon (BrC) are important light-absorbing carbonaceous aerosols in the atmosphere, and it is of great significance to study the climate effects of BrC for regional or global climate change. This paper reviews recent advances in research on the radiative forcing of BrC, its effects on temperature and precipitation, and snow/ice albedo. Recent research suggests that: (1) Climate effects of aerosols can be represented more accurately when including BrC absorption in climate models; the regions with the highest global mean surface BrC concentrations estimated by models are mostly Southeast Asia and South America (biomass burning), East Asia and northeast India (biofuel burning), and Europe and North America (secondary sources); estimates of BrC radiative forcing are quite erratic, with a range of around 0.03-0.57 W m-2. (2) BrC heating lead to tropical expansion and a reduction in deep convective mass fluxes in the upper troposphere; cloud fraction and cloud type have a substantial impact on the heating rate estimates of BrC. The inclusion of BrC in the model results in a clear shift in the cloud fraction, liquid water path, precipitation, and surface flux. BrC heating decreases precipitation on a global scale, particularly in tropical regions with high convective and precipitation intensity, but different in some regions. (3) Uncertain optical properties of BrC, mixing ratio of radiation-absorbing aerosols in snow, snow grain size and snow coverage lead to higher uncertainties and lower confidence in the simulated distribution and radiative forcing of BrC in snow than BC. To reduce the uncertainty of its climate effects, future research should focus on improving model research, creating reliable BrC emission inventories, and taking into account the photobleaching and lense effects of BrC.

Black carbon (BC) exerts potential effect on climate, especially in the Tibetan Plateau (TP), where the cryosphere and environment are very sensitive to climate change. Although transport of atmospheric BC from South and East Asia to the TP has been comprehensively investigated, transport of BC from Central and West Asia (CWA) to the TP and its climate effect on the region have received little attention and are warrant investigation. Therefore, based on the observation and ERA-Interim reanalysis data, this study investigated transport of atmospheric BC from CWA to the TP, its seasonality and climate effect over the TP using WRF-Chem model. On an annual scale, BC from CWA contributes to 5.8% of total BC over the TP. Seasonally, the contribution rates were 5.1%, 5.9%, 6.2%, and 5.7% in spring, summer, autumn, and winter, respectively. The area-averaged surface radiative forcing over the TP induced by BC from CWA ranged from-0.14 to-0.04 W m(-2), with the largest and smallest negative radiative forcing occurring in autumn and winter, respectively. Affected by BC from CWA, the area-averaged surface temperature over the TP increased by 0.033 degrees C in summer, whereas it decreased by 0.002, 0.005, and 0.001 degrees C in spring, autumn and winter, respectively. In the atmosphere over the TP, the positive radiative forcing with values of 0.17, 0.20, 0.04, and 0.07 W m(-2) were induced by BC from CWA in spring, summer, autumn, and winter, respectively. At the top of the atmosphere over the TP, the calculated radiative forcing associated with BC from CWA were 0.08, 0.14,-0.1, and 0.03 W m(-2) in spring, summer, autumn, and winter, respectively. On an annual scale, the radiative forcing in the atmosphere and at the top of the atmosphere over the TP caused by BC from CWA were 0.12 W m(-2) and 0.04 W m(-2), respectively. This study enriched the theoretical connotation of transboundary transport of BC aerosols to the TP.

Black carbon (BC) exerts potential effect on climate, especially in the Tibetan Plateau (TP), where the cryosphere and environment are very sensitive to climate change. Although transport of atmospheric BC from South and East Asia to the TP has been comprehensively investigated, transport of BC from Central and West Asia (CWA) to the TP and its climate effect on the region have received little attention and are warrant investigation. Therefore, based on the observation and ERA-Interim reanalysis data, this study investigated transport of atmospheric BC from CWA to the TP, its seasonality and climate effect over the TP using WRF-Chem model. On an annual scale, BC from CWA contributes to 5.8% of total BC over the TP. Seasonally, the contribution rates were 5.1%, 5.9%, 6.2%, and 5.7% in spring, summer, autumn, and winter, respectively. The area-averaged surface radiative forcing over the TP induced by BC from CWA ranged from-0.14 to-0.04 W m(-2), with the largest and smallest negative radiative forcing occurring in autumn and winter, respectively. Affected by BC from CWA, the area-averaged surface temperature over the TP increased by 0.033 degrees C in summer, whereas it decreased by 0.002, 0.005, and 0.001 degrees C in spring, autumn and winter, respectively. In the atmosphere over the TP, the positive radiative forcing with values of 0.17, 0.20, 0.04, and 0.07 W m(-2) were induced by BC from CWA in spring, summer, autumn, and winter, respectively. At the top of the atmosphere over the TP, the calculated radiative forcing associated with BC from CWA were 0.08, 0.14,-0.1, and 0.03 W m(-2) in spring, summer, autumn, and winter, respectively. On an annual scale, the radiative forcing in the atmosphere and at the top of the atmosphere over the TP caused by BC from CWA were 0.12 W m(-2) and 0.04 W m(-2), respectively. This study enriched the theoretical connotation of transboundary transport of BC aerosols to the TP.

Black carbon (BC) exerts a potential influence on climate, especially in the Arctic, where the environment is very sensitive to climate change. Therefore, the study of climate effects of BC in this region is particularly important. In this study, numerical simulations were performed using the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem) in the Arctic in winter and spring for two years to investigate the atmospheric BC causing changes in surface radiation, meteorology, and atmospheric stability. Generally, WRF-Chem well reproduced the temporal variations of meteorological variables and BC concentration. Numerical simulations showed that BC concentrations in the Arctic in winter were mostly higher than those in spring, and the BC-induced near-surface temperature changes were also stronger. The effects of BC on near-surface water vapor mixing ratio were consistent with the spatial pattern of near-surface temperature changes. That was probably the result of the regional circulation anomaly due to the temperature changes. Additionally, the distributions of near-surface temperature changes and horizontal wind changes also reflected in the distribution of planetary boundary layer height. Ultimately, this study revealed that the downward longwave radiation related to cloudiness changes played an important role for driving near-surface temperature in the Arctic in winter. While in spring, the relatively less changes in near-surface temperature may be the result of the mutual compensation between the surface longwave and shortwave radiation effects. (C) 2020 Elsevier B.V. All rights reserved.

Black carbon (BC) aerosol is a significant, short-lived climate forcing agent. To further understand the effects of BCs on the regional climate, the warming effects of BCs from residential, industrial, power and transportation emissions are investigated in Asian regions during summer using the state-of-the-art regional climate model RegCM4. BC emissions from these four sectors have very different rates and variations. Residential and industrial BCs account for approximately 85% of total BC emissions, while power BCs account for only approximately 0.19% in Asian regions during summer. An investigation suggests that both the BC aerosol optical depth (AOD) and direct radiative forcing (DRF) are highly dependent on emissions, while the climate effects show substantial nonlinearity to emissions. The total BCs AOD and clear-sky top of the atmosphere DRF averaged over East Asia (100-130 degrees E, 20-50 degrees N) are 0.02 and +1.34 W/m(2), respectively, during summer. Each sector's BC emissions may result in a warming effect over the region, leading to an enhanced summer monsoon circulation and a subsequent local decrease (e.g., northeast China) or increase (e.g., south China) in rainfall in China and its surrounding regions. The near surface air temperature increased by 0.2 K, and the precipitation decreased by approximately 0.01 mm/day in east China due to the total BC emissions. The regional responses to the BC warming effects are highly nonlinear to the emissions, which may be linked to the influences of the perturbed atmospheric circulations and climate feedback. The nonuniformity of the spatial distribution of BC emissions may also have significant influences on climate responses, especially in south and east China. The results of this study could aid us in better understanding BC effects under different emission conditions and provide a scientific reference for developing a better BC reduction strategy over Asian regions.

We used an online aerosol-climate model (BCC_AGCM2.0_CUACE/Aero) to simulate effective radiative forcing and climate response to changes in the concentrations of short-lived climatic pollutants (SLCPs), including methane, tropospheric ozone, and black carbon, for the period 2010-2050 under Representative Concentration Pathway scenarios (RCPs) 8.5, 4.5, and 2.6. Under these three scenarios, the global annual mean effective radiative forcing were 0.1, -0.3, and -0.5Wm(-2), respectively. Under RCP 8.5, the change in SLCPs caused significant increases in surface air temperature (SAT) in middle and high latitudes of the Northern Hemisphere and significant decreases in precipitation in the Indian Peninsula and equatorial Pacific. Global mean SAT and precipitation increased by 0.13K and 0.02 mmd(-1), respectively. The reduction in SLCPs from 2010 to 2050 under RCPs 4.5 and 2.6 led to significant decreases in SAT at high latitudes in the Northern Hemisphere. Precipitation increased slightly in most continental regions, and the Intertropical Convergence Zone moved southward under both of these mitigation scenarios. Global mean SAT decreased by 0.20 and 0.44K, and global averaged precipitation decreased by 0.02 and 0.03 mmd(-1) under RCPs 4.5 and 2.6, respectively.