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A declining trend in Indian summer monsoon precipitation (ISMP) in the latter half of the 20th century is a scientifically challenging and societally relevant research issue. Heavy aerosol loading over India is one of the key factors in modulating the ISMP. Using the state-of-the-state-of-the-art chemistry-climate model, ECHAM6-HAMMOZ, the impacts of South Asian anthropogenic sulfate aerosols on the Indian summer monsoon precipitation were investigated against: (1) 2010 La Niña (excess monsoon), (2) 2015 El Niño (deficit monsoon) in comparison to (3) normal monsoon 2016. Sensitivity simulations were designed with 48% enhancement in South Asian SO 2 emissions based on a trend estimated from Ozone Monitoring Instrument (OMI) satellite observations during 2006–2017. The model simulations showed that sulfate aerosols reduce ISMP by 27.5%–43.3 %, while simulations without sulfate loading enhanced ISMP by 23% in 2010 La Niña and reduction by 35% in 2015 El Niño. This paper reports that sulfate aerosols loading over India reduce precipitation by aerosol-induced direct and indirect effects by inducing atmospheric cooling, weakening in the convection, and reduction in moisture transport to Indian landmass. This paper emphasizes the necessity of alternate use of energy to reduce sulfate aerosol emissions to solve water issues in South Asia. [Display omitted] • Sulfate emission reduces Indian summer monsoon precipitation through aerosol-radiation and aerosol-cloud interactions. • Over 27% of the summer monsoon rainfall deficit in a normal year are linked to Asian anthropogenic sulfate emissions. • Sulfate-induced rainfall reduction is the maximum for La Niña year. • SO 2 loading increases atmospheric stability and weakens moisture transport to India. [ABSTRACT FROM AUTHOR]

• Expert technical and economic rationalities overlook political aspects of sustainability. • Local experiences reveal structures and processes that shape inequitable outcomes. • Sustainable developmentality creates a triple-bind for rural mountain residents. • The triple-bind contributes to large numbers migrating from mountain dwellings. • Mountain migration and land abandonment is a political not an inevitable process. Sustainability challenges persist in the central Indian Himalayas (CIH) despite an array of solutions proffered by external experts. This paper interrogates the 'sustainability gaze' of external experts – which reflects attempts to reconcile neoliberal economic growth with environmental conservation within the logics of technical and biophysical rationalities - by exploring local experiences of rapid and uncertain social and environmental change. Three strands of policy and practice shape the gaze: (i) natural hazard mitigation for climate change adaptation; (ii) reducing social vulnerability through pro-poor development; and (iii) increasing resilience through environmental management and conservation. Results challenge narratives that overpopulation causes environmental degradation and changing patterns of migration are a natural process of modernisation in the CIH. Alternative local narratives highlight haphazard and inequitable economic growth, lack of mountain planning and disaster management, inadequate social welfare programmes, and monkey relocation policies as the major sustainability challenges. The paper discusses how the gaze produces 'sustainable developmentality' - a depoliticising process that cultivates multiple and conflicting mountain subjectivities, namely: (i) active community members responsible for mitigating natural hazards, (ii) productive farmers and flexible waged labourers, and (iii) custodians of the environment. This creates a triple-bind for smallholders which has forced huge numbers to migrate from their mountain dwellings with unsustainable outcomes. Exploring local perspectives re-politicises the debate, exposing the contradictions and tensions of the gaze and the broader systemic issues of power and inequity the gaze overlooks. Such insights are crucial for rendering development policies more relevant to mountain residents of the CIH and beyond. [ABSTRACT FROM AUTHOR]

South Asian air pollutants exert substantial effect on the climate and environment change over the Tibetan Plateau (TP). This paper investigates the trans-boundary transport of PM 10 , PM 2.5 , and O 3 from South Asia to the TP via WRF-Chem sensitive analysis. It is found that PM 10 , PM 2.5 , and O 3 over South Asia are mainly sourced from anthropogenic sources. South Asian emissions contribute up to 54% of PM 10 (PM 2.5) in the TP in the pre-monsoon season. For O 3 , the highest contribution of 18.13% is in the monsoon season, while the lowest contribution of 8.67% is in the winter season. To evaluate the respective contributions of anthropogenic and biomass burning emissions in South Asia to PM 10 , PM 2.5 , and O 3 in the TP, anthropogenic and biomass burning emissions in South Asia are considered separately. The results show that the largest percentage contribution of PM 10 (PM 2.5) from South Asian anthropogenic emissions to PM 10 (PM 2.5) in the TP with value of 35.86% (37.77%) occurs in winter, while the lowest percentage contribution of 16.52% (16.77%) appears in the monsoon season. For O 3 , the largest contribution of 17.74% from South Asian anthropogenic emissions appears in the monsoon season, whereas the lowest contribution of 8.59% occurs in winter. Compared to the anthropogenic emissions, the biomass burning emissions in South Asia have a relative less contribution to PM 10 , PM 2.5 , and O 3 in the TP. The largest contribution of PM 10 (PM 2.5) from South Asian biomass burning emissions to PM 10 (PM 2.5) in the TP is 20.04% (18.37%) in the pre-monsoon season. Conversely, the lowest contribution of 0.58% (0.53) appears in the monsoon season. O 3 from South Asian biomass burning emissions contributes <1% to O 3 in the TP in each season, implying that the biomass burning emissions in South Asia have little effect on O 3 in the TP. This study is of great significance to the ecological environment protection for the TP. • Contributions of South Asian emissions to PM 10 , PM 2.5 , and O 3 in the TP are quantified. • Anthropogenic emissions in South Asia have a larger contribution to PM 10 , PM 2.5 , and O 3 in the TP. • O 3 from South Asian biomass burning emissions contributes <1% to O 3 in the Tibetan Plateau. [ABSTRACT FROM AUTHOR]

Extreme climate events are hotspots in global change. However, research on the changes in future compound events and population exposure is still limited. Leveraging from the data of the sixth phase of the Coupled Model Intercomparison Project (CMIP6), this paper aims to analyze the temporal and spatial changes of global compound temperature and precipitation extreme events in the future. We also predict the risk of population exposure and quantify the contribution of different factors to exposure. The results show that: (1) In the next 80 years, compound hot-dry event (CHDE) will increase at a rate of 0.02, 0.03, and 0.08 days per decade under the three scenarios of SSP1–2.6, SSP2–4.5 and SSP5–8.5, respectively. By comparison, compound hot-humidity event (CHHE) shows a downward trend under the three scenarios, with a downward rate of 0.01, 0.02, and 0.11 days per decade, respectively. (2) Under the SSP1–2.6 and SSP2–4.5 scenarios, CHDE and CHHE have two or more mutation points. Under the SSP5–8.5 scenario, CHDE shows a significant upward and CHHE shows a significant downward trend in the middle and late 21st century. These two indices exhibit periodic changes in all three scenarios (3) South Asia, West Asia, and Northeast Africa have higher CHDE values, while regions with higher CHHE values are located in North Asia and Greenland. (4) Climate change is a major factor affecting population exposure. For CHDE, climate, population, and their synergistic effects contribute about 75%, 20%, and 5% to the exposure, respectively. For CHHE, the contributions of these three factors are 85%, 10%, and 5% respectively. These findings provide scientific guidance for the rational formulation of population policies, the effective avoidance of climate disaster risks and the protection of human health. • Frequency of hot-dry events and hot-humidity events will increase and decrease, respectively, in the future. • There are abrupt points and periodicity in the future time series of compound temperature and precipitation extremes. • Asia is projected to have the greatest exposure and climate change contributes the most to exposure. [ABSTRACT FROM AUTHOR]

Aerosols over the Tibetan Plateau (TP) play an important role in the regional and global climate change and ecological environment. The Second Tibetan Plateau Scientific Expedition and Research Program (STEP) carried out observation experiment at the Nam Co Station for Multisphere Observation and Research, Chinese Academy of Sciences (Nam Co Station, 30°46′N, 90°59′E, 4730 m) in the central TP from August 5 to September 11, 2020. This paper investigated the aerosol optical properties and its potential sources over Nam Co region. The main results are as follow: the average aerosol optical depth was 0.025 during the observation period; the average black carbon (BC) concentration and aerosol number concentration was 37 ng/m3 and 129 N/cm3, respectively; the diurnal variation and vertical distribution of aerosol were affected by the local meteorological elements. Frequent southerly winds during the summer monsoon led to a certain contribution of South Asia to the BC concentration in Nam Co region. And particles from the Taklimakan Desert led to dramatic increasing of aerosol number concentration over Nam Co region. The aerosol optical characteristics and influencing factors over the central TP were analyzed, which is beneficial to further study the influence of aerosols over the TP on regional and global weather and climate. • Optical properties of aerosol over Nam Co station were observed by the STEP of China. • Nam Co region was generally influenced by BC from South Asia, local pollution emissions and north particles. • The average of AOD, depolarization ratio and BC over Nam Co station was 0.026, 0.033 and 37 ng/m3, respectively. [ABSTRACT FROM AUTHOR]

Known as the "third pole" and "water tower of Asia", the Tibetan Plateau (TP) is the home to the largest number of glaciers in the mid-latitudes and one of the most sensitive areas to global climate change due to its special geographical location and powerful thermodynamic effects. In recent years, the TP has been affected by exogenous pollutants and the concentrations of some pollutants have shown an increasing trend, especially light-absorbing aerosols (LAAs), when ice core records, ground- and aircraft-based field campaigns and satellite technology enabled synthesized monitoring. The enhanced warming of the vast majority of regions in TP, together with Arctic warming, and snow/ice decline, represents credible evidence of anthropogenic climate change. This paper provides a comprehensive review of studies on the sources, characteristics and climate impacts of LAAs over the TP. Adjacent to the two major emission sources of LAAs in East Asia and South Asia, the unique geographical location and climatic characteristics of the TP make it possible for TP LAAs to cause atmospheric warming and accelerated glacier melting, affecting the hydrological cycle in South Asia, East Asia and even the Northern Hemisphere, thus causing a series of serious environmental and social problems. LAAs, such as black carbon and dust, can strongly absorb solar radiation and and have significantly influence on climate change. Moreover, light-absorbing impurities (LAIs) on snow/ice can reduce the snow/ice albedo and further accelerate the snow/ice melting. Both LAAs and LAIs over the TP can induce thermodynamic feedback processes, cause significant warming of the TP and then lead to a strengthening of the early monsoon and affect the subsequent evolution of the monsoon. Many mechanisms have been proposed forth regarding how TP LAAs modulate the phase, intensity, and amplitude of the Asian climate system. A wide range of theoretical, observational, and modeling findings on TP LAAs and their climate impacts are synthesized, in which dust aerosols from drylands and black carbon from biomass burning are considered leading components. By coupling an integrated approach with state-of-the-art modeling, high temporal and fine spatial resolution remote sensing observations with increasing sampling over the TP will provide further insights into TP aerosols. • Light-absorbing aerosols warm the Tibetan Plateau, further influence climate system • The external input of light-absorbing aerosols over the Tibetan Plateau is dominant • Climate effects of light-absorbing aerosols or impurities in snow is divergent [ABSTRACT FROM AUTHOR]