To achieve the goal of carbon neutrality, China is projected to significantly reduce anthropogenic aerosols in addition to greenhouse gases. Here, the future changes in East Asian summer monsoon (EASM) and weather extremes responding to the idealized local emission reductions of anthropogenic aerosols (AA) in China are investigated based on time-slice simulations in an aerosol-climate model together with a localized carbon neutral emission scenario, while greenhouse gases and other anthropogenic climate forcers are kept at the present-day (2015) levels. The AA reduction in China leads to a positive change in June-July-August (JJA) mean effective radiative forcing over eastern China in 2030 and 2060s, along with a 0.2 degrees C-0.4 degrees C warming, respectively. It intensifies the temperature difference between land and ocean, and increases the precipitation over eastern China. Multiple EASM indices show that EASM intensity in JJA is estimated to be strengthened in the future, because of the AA decline in China. The AA emissions reduction toward carbon neutrality in China also presents a potential side effect of intensifying the summertime extreme temperatures and precipitation in China. This study reveals the important role of reductions of AA emissions in influencing EASM and weather extremes, which warrants careful assessment in the emission policymaking process prior to the implementation of mitigation strategies.

Thawing permafrost alters climate not only through carbon emissions but also via energy-water feedback and atmospheric teleconnections. This review focuses on the Tibetan Plateau, where strong freeze-thaw cycles, intense radiation, and complex snow-vegetation interactions constitute non-carbon climate responses. We synthesize recent evidence that links freeze-thaw cycles, ground heat flux dynamics, and soil moisture hysteresis to latent heat feedback, monsoon modulation, and planetary wave anomalies. Across these pathways, both observational and simulation studies reveal consistent signals of feedback amplification and nonlinear threshold behavior. However, most Earth system models underrepresent these processes due to simplifications in freezethaw processes, snow-soil-vegetation coupling, and cross-seasonal memory effects. We conclude by identifying priority processes to better simulate multi-scale cryosphere-climate feedback, especially under continued climate warming in high-altitude regions.

Refractory black carbon (rBC) is a primary aerosol species, produced through incomplete combustion, that absorbs sunlight and contributes to positive radiative forcing. The overall climate effect of rBC depends on its spatial distribution and atmospheric lifetime, both of which are impacted by the efficiency with which rBC is transported or removed by convective systems. These processes are poorly constrained by observations. It is especially interesting to investigate rBC transport efficiency through the Asian Summer Monsoon (ASM) since this meteorological pattern delivers vast quantities of boundary layer air from Asia, where rBC emissions are high to the upper troposphere/lower stratosphere (UT/LS) where the lifetime of rBC is expected to be long. Here, we present in situ observations of rBC made during the Asian Summer Monsoon Chemistry and Climate Impact Project of summer, 2022. We use observed relationships between rBC and CO in ASM outflow to show that rBC is removed nearly completely (>98%) from uplifted air and that rBC concentrations in ASM outflow are statistically indistinguishable from the UT/LS background. We compare observed rBC and CO concentrations to those expected based on two chemical transport models and find that the models reproduce CO to within a factor of 2 at all altitudes whereas rBC is overpredicted by a factor of 20-100 at altitudes associated with ASM outflow. We find that the rBC particles in recently convected air have thinner coatings than those found in the UTLS background, suggesting transport of a small number of rBC particles that are negligible for concentration.

Floods in India are recurring natural disasters resulting from extreme precipitation during the summer monsoon season (June-September). The recent flood in North India in July 2023 caused substantial damage to lives, agriculture, and infrastructure. However, what led to the 2023 North India flood and the role of atmospheric and land drivers still need to be examined. Using in situ observations, satellite data, and ERA5 reanalysis combined with hydrological and hydrodynamical modeling, we examine the role of land and atmospheric drivers in flood occurrence and its impacts. Extreme precipitation in a large region during 7-10 July 2023 created favorable conditions for the flood in the hilly terrains and plains of north India. More than 300 mm of precipitation fell in just 4 days, which was eight times higher than the long-term average (2001-2022). Anomalously high moisture transport over northern India was recorded on 7 July 2023, making atmospheric conditions favorable for intense landfall. Increased column water vapor and specific humidity at different pressure levels confirmed the continuous moisture presence before the extreme rainfall that caused floods in northern India from 7 to 12 July 2023. Atmospheric and land (high antecedent soil moisture) conditions contributed to a more than 200% rise in streamflow at several gauge stations. Satellite-based flood extent shows a considerable flood inundation that caused damage in the Sutlej and Yamuna River basins. Our findings highlight the crucial role of the favorable land and atmospheric conditions that caused floods and flash floods in north India in July 2023. In July 2023, North India experienced a severe flood that caused significant damage to lives, agriculture, and infrastructure. However, the exact causes of this flood have yet to be examined. Using in situ, satellite, and reanalysis data, we examined the drivers of the flood. Favorable atmospheric and land conditions created a unique situation that led to a significant flood in north India. For instance, extreme precipitation during 7-10 July enhanced antecedent soil moisture conditions in the hilly and plain regions. Anomalously high moisture transport caused intense rainfall, which, combined with high soil moisture, produced high runoff and streamflow conditions. Flood inundation caused damage to the Sutlaj and Yamuna river basins. Our findings show the need to monitor soil moisture and atmospheric processes for early warning of floods in hilly regions. The flood in North India in July 2023 caused substantial damage to lives, agriculture, and infrastructure Anomalously high moisture transport over northern India created atmospheric conditions favorable for intense landfall High antecedent soil moisture and extreme precipitation caused the north India flood in 2023

In India, particularly within its Northeastern territories, landslides triggered by rainfall following dry periods are a major concern, consistently causing extensive damage to both life and infrastructure. This study focuses on mitigating their impact through preemptive measures, with an emphasis on analyzing slope stability to determine critical intervention points. The investigation includes experimental tests on soil samples to assess key parameters, such as soil matric suction and unconfined compressive strength, alongside an analysis of slope failures during the 2017 monsoon in Mizoram's Lunglei district. Employing Soil-Water Characteristic Curves (SWCC) derived from ASTM D5298-10 standards and a microwave drying technique for preparing soil samples, the research evaluates the condition of the slopes before and after monsoonal rains. This study utilizes a blend of numerical modeling and empirical laboratory investigations to explore the factors contributing to slope instability. The findings underscore the necessity of advanced landslide warning systems, suggesting that a deeper understanding of rainfall-induced slope failures could significantly enhance disaster preparedness and reduce potential damages.

Knowledge of the paleoclimatic record of the northeastern Tibetan Plateau (NETP) can potentially improve our understanding of the evolution of the Asian summer monsoon (ASM). However, the history of climate change and inferred spatial extent of the ASM on the NETP since the last deglaciation remain unclear. Here, we use several environmental proxies from the sediments of Hala Lake (beyond the modern limit of ASM), including chironomids, loss-on-ignition, grain size and element data, to explore the climatic history of the NETP and the northern boundary of the ASM since the last deglaciation. The results document a series of climatic events during the deglaciation, including Heinrich Event 1, the Bolling-Allerod interstadial and the Younger Dryas event. The records also reveal the timing of the megathermal and precipitation maximum, the lake-level maximum, and strongest chemical weathering, which occurred during similar to 10-7 ka. The inferred precipitation maximum during the early Holocene in the Hala Lake basin, which can be verified by the simulated precipitation change, is consistent with that in typical Indian summer monsoon (ISM) regions, suggesting that the ISM has penetrated into Hala Lake basin at that time. The monsoon-dominated climate in the Hala Lake basin during the early Holocene and the westerlies-dominated climate in the arid central Asia indicate that the maximum areal extent of the ASM on the NETP since the last deglaciation lay to the northwest of Hala Lake basin. In combination with other published records, the northernmost boundary of the ASM over China since the last deglaciation has been tentatively delineated, to shed some lights on this long-standing debate.

The NCAR Community Earth System Model is used to study the influences of anthropogenic aerosols on the Indian summer monsoon (ISM). We perform two sets of 30-year simulations subject to the prescribed perpetual SST annual cycle. One is triggered by the year 2000 climatology anthropogenic aerosol emissions data over the Indian Peninsula (referred to as AERO), and the other one is by the year 1850 (referred to as CTL). Only aerosol direct effects are included in the experiments. In our results, the transition of ISM in AERO relative to the CTL exhibits a similar ensemble-mean onset date with a larger spread, and more abrupt onset in late spring, and an earlier but more gradual withdrawal in early fall. The aerosols-induced circulation changes feature an upward motion over the northeastern Indian Peninsula and strengthened anticyclonic circulation over the Arabia Sea in the pre-monsoon season, and a northward shift of monsoon flow in the developed monsoon period along with strengthened local meridional circulation over northern India. The strengthened anticyclonic circulation over Arabia Sea caused a 16% increase in natural dust transport from the Middle East in the pre-monsoon season. The elevated aerosol heating over Tibet causes stronger ascending motion in the pre-monsoon period that leads to earlier and more abrupt ISM onset. The earlier monsoon withdrawal is attributed to the aerosol-induced anticyclonic flow within 10 & DEG;-25 & DEG;N and cyclonic flow within 0 & DEG;-10 & DEG;N over eastern India and Bay of Bengal that resemble the ISM seasonal transition in September.

Remote region is normally considered a receptor of long-range transported pollutants. Monitoring stations are important platforms for investigating the atmospheric environment of remote regions. However, the potential contribution of very local sources around these stations may produce important influences on its atmospheric environment, which is still barely studied. In this study, major ions of precipitation were investigated simultaneously at a typical remote station (Nam Co station) and other sites nearby on the Tibetan Plateau (TP) - the so-called The Third Pole in the world. The results showed that despite low values compared to those of other remote regions, the concentrations of major ions in precipitation of Nam Co station (e.g., Ca2+: 32.71 mu eq/L; SO42- : 1.73 mu eq/L) were significantly higher than those at a site around 2.2 Km away ( Ca2+: 11.47 mu eq/L; SO42- : 0.64 mu eq/L). This provides direct evidence that atmospheric environment at Nam Co station is significantly influenced by mineral dust and pollutants emitted from surface soil and anthropogenic pollutants of the station itself. Therefore, numbers of other related data reported on the station are influenced. For example, the aerosol concentration and some anthropogenic pollutants reported on Nam Co station should be overestimated. Meanwhile, it is suggested that it is cautious in selecting sites for monitoring the atmospheric environment at the remote station to reduce the potential influence from local sources.

The northernmost margin of the East Asian summer monsoon (NMEASM) is the northernmost position that the East Asia summer monsoon (EASM) can reach. NMEASM has obvious multi-scale variability, and well reflects the wet/dry climate variability in northern China. Predicting the location change of the NMEASM is important for understanding future East Asian climate change. However, the variability of the NMEASM has not been studied extensively, and its underlying mechanisms have not been clarified. To explore the movement of the NMEASM and its causes, we use reanalysis datasets to evaluate the NMEASM index from 1979 to 2018. The NMEASM indicates a decreasing trend over 40 years and a significant abrupt point in 2000, which is positively correlated with the Tibetan Plateau snow cover before 2000 and the Siberian snow cover after 2000 in spring. The decreased Siberian snow cover increases the soil temperature and decreases the atmospheric baroclinicity over Mongolia and northern China after 2000. The decreased atmospheric baroclinicity induces the dipole mode of anticyclonic anomaly over Mongolia and northern China and the cyclonic anomaly over the Sea of Japan by modulating the wave activity flux (WAF). The WAF's southeastward propagation strengthens the anticyclonic anomaly over Mongolia and northern China and the cyclonic anomaly over the Sea of Japan, which weakens the upward movement and water vapor transport, respectively. Hence, the decreased Siberian snow cover in spring modulates the precipitation over Mongolia and northern China and the southward movement of NMEASM by turbulent westerly circulation.

Aerosol mixtures, which are still unclear in current knowledge, may cause large uncertainties in aerosol climate effect assessments. To better understand this research gap, a well-developed online coupled regional climate-chemistry model is employed here to investigate the influences of different aerosol mixing states on the direct interactions between aerosols and the East Asian summer monsoon (EASM). The results show that anthropogenic aerosols have high-level loadings with heterogeneous spatial distributions in East Asia. Black carbon aerosol loading accounts for more than 13% of the totals in this region in summer. Thus, different aerosol mixing states cause very different aerosol single scattering albedos, with a variation of 0.27 in East Asia in summer. Consequently, the sign of the aerosol instantaneous direct radiative forcing at the top of the atmosphere is changed, varying from - 0.95 to + 1.50 W/m(2) with increasing internal mixing aerosols. The influence of aerosol mixtures on regional climate responses seems to be weaker. The EASM circulation can be enhanced due to the warming effect of anthropogenic aerosols in the lower atmosphere, which further induces considerable aerosol accumulation associated with dynamic field anomaly, decrease in rainfall and so on, despite aerosol mixtures. However, this interaction between aerosols and the EASM will become more obvious if the aerosols are more mixed internally. Additionally, the differences in aerosol-induced EASM anomalies during the strongest and weakest monsoon index years are highly determined by the aerosol mixing states. The results here may further help us better address the environmental and climate change issues in East Asia.