This session addresses: the strong and spatially complex trends in temperature, hydroclimate, air quality, and extreme events driven by aerosol changes over the historical era, and those expected in the near future; the interplay between aerosol-driven changes and those induced by other forcing factors; and their extensions to climate risk and impact studies. We encourage contributions based on model and observation-based approaches to investigate the effects of aerosols on regional decadal climate variability and extremes, tropical-extratropical interactions and teleconnections, and the interactions with modes of variability such as the NAO, ENSO, AMV, and PDO. This year we especially welcome studies focusing on the climate effects of African air pollution, notably how absorbing aerosols influence Sub-Saharan precipitation, and any analyses using the RAMIP dataset. We also welcome focused studies on aerosol influences on monsoon systems, midlatitude and Arctic responses, extreme temperature and precipitation, atmospheric and oceanic circulation changes, tropical cyclones, and daily variability, using for example CMIP6 projections, large ensemble simulations, or specifically designed experiments. We also encourage studies focusing on climate risk and concrete regional impacts on nature and society resulting from changes in anthropogenic and natural aerosol emissions.
Orals: Wed, 6 May, 10:45–12:30 | Room M1
Over the past several decades, the proportion of solar radiation reflected back into space has declined, accelerating the accumulation of heat within the Earth system. Satellite observations provide compelling evidence for the loss of reflective marine clouds and rising sea surface temperatures in the Northern Hemisphere. Natural climate variability is unlikely to be the primary cause of this cloud reflectivity decrease, which is poorly understood. Here we show that the marine cloud reflectivity, as measured by the shortwave cloud radiative effect, decreased on average by 2.8 +/- 1.2% per decade in the combined North Atlantic and Northeast Pacific regions between 2003 and 2022. The majority of the Earth System Models we analyzed simulated a cloud reflectivity decrease that is significantly less than observed in these regions. Our simulations using an updated aerosol-climate model show that reductions in sulfur dioxide and other air pollutants accounted for 69% (range 55 to 85%) of the decrease through aerosol-cloud interactions, consistent with the observed aerosol optical depth and cloud droplet number trends. These emission reductions are projected to persist over the next few decades, which raises the prospect of a continuing cloud reflectivity decrease and warming enhancement in these regions and globally.
How to cite: von Salzen, K., Akingunola, A., Cole, J., Digby, R., Doherty, S., Fraser-Leach, L., Gryspeerdt, E., Sigmond, M., and Wood, R.: Extensive Decline of Reflective Clouds over the North Atlantic and Northeast Pacific from Aerosol Reductions, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3599, https://doi.org/10.5194/egusphere-egu26-3599, 2026.
The Indo-Gangetic Plain (IGP), home to over 900 million people, experiences some of the world's worst air pollution, with PM2.5 concentrations routinely exceeding WHO guidelines by factors of 5-10. While seasonal patterns of aerosol loading are well documented, driven by monsoon rainfall cycles and emission variations, the synoptic meteorological controls governing day-to-day pollution extremes remain poorly understood. This limits our ability to project future air quality under changing atmospheric circulation patterns and to evaluate whether climate models accurately represent the circulation-aerosol coupling essential for reliable near-term climate projections over South Asia.
We identify and characterise distinct synoptic circulation regimes over the IGP and quantify their control on aerosol loading and air quality. Using circulation classification applied to reanalysis data combined with satellite-derived aerosol observations and pollution measurements, we isolate how atmospheric circulation variability modulates PM2.5 and aerosol optical depth independently of emission changes. Given the IGP's unique valley topography, we find air quality shows distinct responses to meteorological variability across seasons, with implications for both climate model evaluation and future projections. We extend this analysis to the UK Earth System Model to assess whether current generation climate models capture the observed sensitivity of aerosol loading to circulation patterns. This is critical because future air quality depends on both emission pathways and changes to circulation regime frequency under climate change.
This work has important implications for climate risk assessment in South Asia. As the monsoon system responds to global warming, shifts in circulation patterns could amplify or offset emission-driven air quality trends, creating pollution hotspots even under declining emissions, or provide ventilation that moderates pollution despite stable emissions. The results could inform emission reduction strategies by clarifying when and how meteorological conditions determine pollution outcomes, and establish process based constraints for models projecting future climate risks in South Asia.
How to cite: Bhandekar, A., Wilcox, L., Lawrence, B., Abraham, N. L., and O'Connor, F.: Synoptic circulation control on aerosol loading over the Indo-Gangetic Plain: Implications for regional air quality, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11733, https://doi.org/10.5194/egusphere-egu26-11733, 2026.
India has witnessed a significant rise in surface temperature during the pre-monsoon season, driving more intense, frequent, and prolonged heatwaves, particularly over the northwest and central regions of the country. While there is a clear consensus on the role of greenhouse gases driving global warming, the role of anthropogenic aerosols, particularly absorbing ones such as black carbon, brown carbon, and dust, on regional warming remains uncertain and is less understood. While scattering aerosols dominate in many regions, India exhibits a high loading of absorbing aerosols, mainly mineral dust and black carbon from natural transport and combustion sources. These absorbing aerosols can offset aerosol-induced cooling and amplify regional near-surface warming. These absorbing aerosols trap solar radiation, heat the atmosphere, and stabilize the atmospheric boundary layer, further amplifying the heatwave conditions by offsetting surface cooling. Studies through observations and model simulations have linked the possible links between the elevated absorbing aerosols and heat extremes through strong radiative forcing and an increase in shortwave energy to the surface layer. However, long-term observational evidence quantifying the relationships between absorbing aerosols and temperature extremes (for both dry and moist heat) over India is yet to be established, motivating this study.
For this, we obtained the pre-monsoon season (March–June; MAMJ) absorbing aerosol and extreme heat data over India (66.5°- 100.5°E; 6.5°-36.5°N) for 1980-2024. The Absorbing Aerosol Index (AAI) is used as a qualitative measure of UV‐absorbing aerosols, obtained from the TOMS satellite record (1980–2004) and the OMI instrument (2005–2024). For extreme heat, we used daily maximum temperature (Tmax) obtained from the Indian Meteorological Department (IMD) to characterize dry heat, while we calculated wet bulb temperature (WBT) by combining Tmax from IMD and relative humidity from ERA5 datasets to define moist heat. We further computed the temporal season mean trends of variables along with their statistical significance at a 95% confidence level. We selected 3 boxes based on significant trends and reported heatwave-prone regions over northwest, eastern, and southern India to analyze the co-evolution of AAI and extreme heat variables.
We found substantial positive trends in season mean AAI and temperature variables across India, with an approximate rate of 0.25 units per decade, ~0.20°C per decade (dry heat), and ~0.2-0.4°C per decade (moist heat), respectively. The increase is highly significant in north-central India in the case of Tmax and AAI, while Central and eastern India show significance for moist heat. The consistent elevated summer temperatures in north-central India are in agreement with scientifically recognized meteorological conditions such as North Atlantic blocking creating high-pressure systems aiding the role of absorbing aerosols in amplifying heat stress. Meanwhile, moist heat increases are linked to rises in pre-monsoon humidity, which are associated with increases in irrigation and sea-surface temperature across India. The current findings have significant implications for coordinated climate and air-quality action to reduce aerosol-driven climate risks associated with extreme heat at regional scales.
How to cite: Modak, A., Tiwari, D., Mondal, A., and Venkataraman, C.: Absorbing aerosols and rising dry–moist heat extremes over India: Evidence of a strengthening air pollution–climate nexus, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21786, https://doi.org/10.5194/egusphere-egu26-21786, 2026.
Extreme rainfall events in India, causing floods and droughts, damage lives and livelihoods and thereby significantly impact agriculture production, natural and constructed landscapes, water resources, and the economy. This part of the world is also a global hotspot for air pollution due to the increase of anthropogenic aerosols since the late 20th century. Aerosols influence the radiation budget and cloud microphysical and dynamical processes, thus influencing monsoon rainfall patterns and trends. However, temporal modulations in monsoon rainfall over the Indian subcontinent, characterized by wet and dry spells, are yet to be understood in the context of the role of enhanced anthropogenic aerosol emissions. To address this gap, in this study, we examine the link between increased aerosol levels and dry and wet spell characteristics of the Indian summer monsoon of the recent era (2001-2025), using observations and model simulations (ECHAM-HAM), made with a regionally representative Indian emission inventory.
We find aerosol-induced drying of both wet and dry rainfall extremes, in the recent period, over the Indian core monsoon region, using Indian Meteorological Department (IMD)’s rainfall and satellite-derived Moderate Resolution Imaging Spectroradiometer (MODIS) aerosol optical depth (AOD) datasets. In the recent era, aerosol enhancements correlate with increasing dry spells but decreasing wet spells, as well as, decreasing rainfall intensity in both wet and dry spells. Model simulations reveal aerosol-induced stabilization and reduction in convective potential energy, inhibiting upward moisture transport. There is also a cloud microphysical effect, reducing cloud drop size and inhibiting rainout. This study illustrates how high aerosol pollution levels over India can lead to rainfall deficits, affecting the region's water supplies and exacerbating climate risks.
How to cite: Venkataraman, C., Cherian, R., Gulzar, A., Bhattacharya, A., and Mondal, A.: Role of anthropogenic aerosols in modulating wet and dry extremes of Indian summer monsoon rainfall, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8817, https://doi.org/10.5194/egusphere-egu26-8817, 2026.
Geopolitical tensions in Eastern Europe underscores the urgency of addressing the climatic and radiological consequences of a regional nuclear conflict. Using an Earth System Model, we explore the fallout from a hypothetical frontline conflict involving air- and surface-burst detonations near the Ukraine-Russia border, releasing substantial amounts of aerosol particles (Black Carbon (BC)) and radionuclides into the stratosphere. The extended stratospheric lifetime of BC induces hemispheric climate disruption: the Northern Hemisphere cools by ~1 °C in year-1, with anomalies of −5 °C in Russia and −4 °C in the United States; surface solar radiation declines by ~30 W m⁻² over the US; and precipitation decreases by ~40% across mid-latitude croplands. Stratospheric warming alters subtropical and polar jets, displacing the Intertropical Convergence Zone ~2–6° southward, delaying climate recovery. To contrast the impacts of a high- versus low-latitude nuclear conflict, we compare the hypothetical Ukraine-Russia conflict with the India-Pakistan case, the latter being the most extensively studied regional nuclear conflict in past literature. We examine its impacts on global and regional climate, the trajectory of long-term climate recovery, and both short- and long-term radiological fallout. These findings underscore the importance of nuclear-risk reduction and provide a robust benchmark for food-security and humanitarian-impact assessments.
How to cite: Ranjithkumar, A., Mayne, N., C. Jones, A., and M. Haywood, J.: Nuclear Conflict in Eastern Europe: Climate Disruption & Radiological Fallout, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5555, https://doi.org/10.5194/egusphere-egu26-5555, 2026.
Arid and semi-arid regions are highly sensitive to hydroclimate changes. In recent decades, precipitation and evapotranspiration have declined across vast global drylands, posing critical challenges to water security and fragile ecosystems. However, these drying trends remain poorly understood and inadequately represented in climate models. Here, using observations and CMIP6 multi-model simulations, we interpret hydroclimatic changes in (semi-)arid regions and associated model biases by presenting a theoretical framework. From an energetic perspective, precipitation and evapotranspiration changes are directly linked to climate forcings through variations in atmospheric diabatic cooling (δQ), which is primarily governed by the response of surface sensible heat flux (δSHdown) to surface shortwave radiation changes (δDSSR). Reanalysis and single-forcing simulations reveal that aerosol surface shortwave radiative effects—rather than greenhouse gases—dominate hydrological changes in dry regions, particularly in the Northern Hemisphere. Since the 1970s, aerosol emissions have increased δDSSR and reduced δSHdown, with the consequent decreases in δQ driving the observed drying trends. In CMIP6 simulations, the substantial underestimation of aerosol-induced solar brightening contributes to pronounced discrepancies with observations. By highlighting the critical role of aerosol effects, this work provides an effective approach for understanding and projecting dryland hydroclimatic responses to shortwave radiative forcings under broader scenarios.
How to cite: zhang, Y., Samset, B., Leung, R., Wilcox, L., and Westervelt, D.: Aerosol Emissions Drive Observed and Modeled Hydrological Trends in Arid and Semiarid Regions , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15915, https://doi.org/10.5194/egusphere-egu26-15915, 2026.
Observations show a significant increase in austral summer (December–February, DJF) precipitation over Madagascar and a dipole over southern Africa since the mid-twentieth century, with implications for unique and biodiversity-rich ecosystems in a recognized global biodiversity hotspot. Yet the physical drivers of these long-term changes remain unclear. Over the same period, rapidly increasing anthropogenic aerosol emissions from Asia substantially altered hemispheric energy distributions and are known to influence remote hydroclimate through large-scale atmospheric circulation adjustments. However, their impacts on African rainfall have not been systematically assessed. We addressed this knowledge gap using historical simulations from Coupled Model Intercomparison Project phase 6 (CMIP6) models and idealized single-forcing experiments from the Precipitation Driver Response Model Intercomparison Project (PDRMIP). Our results suggest that Asian anthropogenic aerosol emissions played a key role in the observed increase in austral summer precipitation over Madagascar and southern Africa from 1930 to 2000 alongside the influence of internal variability. Increased sulfate aerosol emissions over Asia led to regional surface cooling and strengthened interhemispheric temperature and sea-level pressure gradients. This caused a southward shift of the Intertropical Convergence Zone (ITCZ) and the associated Hadley circulation, which resulted in enhanced moisture convergence and increased precipitation over Madagascar. In contrast, after 2000, rapid reductions in Asian aerosol emissions reversed the circulation response and contributed to declining precipitation over Madagascar and southern Africa. Applying this physical framework to near-future scenarios from the Regional Aerosol Model Intercomparison Project (RAMIP) further indicates that aerosol emission reductions will continue to drive substantial hydroclimatic adjustments. These precipitation changes from 2000 to 2020 are accompanied by increased vapor pressure deficit (VPD) and reduced leaf area index (LAI) over Madagascar and southern Africa, consistent with increased vegetation water stress. Taken together, our findings highlight how remote anthropogenic aerosol forcing can influence southern African hydroclimate and moisture-sensitive forests, underscoring the broader current and near-future implications for forests and terrestrial ecosystems in the region.
How to cite: Sheng, B., Bollasina, M., Gagnon, A., Wilcox, L., Reynolds, T., Beckett, C., and Li, Q.: Long-Term Variability of Southern African Hydroclimate Strongly Modulated by Asian Anthropogenic Aerosols, with Implications for Regional Ecosystems, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4112, https://doi.org/10.5194/egusphere-egu26-4112, 2026.
Black Carbon (BC) aerosols are short-lived climate pollutants with uncertain climate impacts. Growing observational records over the past two decades increasingly constrain the dynamics of atmospheric BC. This assessment also utilized the expanding in situ observational records to compare and evaluate emission inventories and global model estimates of BC sources, atmospheric burdens, lifetimes with respect to deposition, solar absorption and radiative effects.
Isotopic fingerprinting of atmospheric BC reveals significant regional differences between biomass and fossil fuel combustion sources, with Sub-Saharan Africa (fbiomass-burning 93±3%), South Asia (56±7%) and East Asia (28±5%). These are broadly consistent with a set of commonly used emission inventories.
Emissions and columnar measurements indicate recent BC declines in South America and East Asia, continued moderate reductions in Europe and North America, and recent stabilization in Africa and South Asia.
The global mean mass absorption coefficient (MAC550) of atmospheric BC is 12.3±5.8 m2/g (151 datasets) and highest in Africa, Europe and South Asia. This is higher than in earlier assessments that focused on near-source measurements. The enhancement (E-MAC550) during long-range transport (ageing) is similar across regions (1.6±0.4).
Long-term observations show that models overestimate BC deposition fluxes while underestimating both concentrations and sunlight absorption in high-pollution regions. This has implications for humidity, clouds, precipitation and climate forcing. Model simulations of aerosol absorption optical depth and the direct radiative forcing ratio between surface and top of atmosphere still underestimate observations by factors of 2 and 1.5, respectively.
Further progress in understanding BC’s role in the climate system will require more extensive intercomparisons between observations, emission inventories, and climate models. Such advances will also strengthen the scientific basis for mitigation policies.
How to cite: Gustafsson, Ö., Budhavant, K., Chimurkar, N., Clarke, S., Dreyfus, G., Gong, X., Klimont, Z., Klingmüller, K., Kim, S.-W., Lelieveld, J., Myhre, G., Nair, H., Peng, J., Ramanathan, V., Rana, A., Remani, M., Satheesh, S., Venkataraman, C., and Zhang, Q.: Observational Constraints on Atmospheric Black Carbon in the Climate System, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14479, https://doi.org/10.5194/egusphere-egu26-14479, 2026.
Posters on site: Wed, 6 May, 16:15–18:00 | Hall X5
The East Asian Summer Monsoon (EASM) has been shown to be sensitive to changes in local and remote aerosol emissions in multiple generations of climate models. Global increases in anthropogenic aerosol cause cooling, especially over Northern Hemisphere land, leading to a southward shift in the ITCZ, a weakened land-sea temperature gradient, and a weakened EASM. Local cooling from local aerosol increases act to weaken the land-sea temperature contrast, and thus the EASM, while the advection of cold air and circulation adjustments resulting from increases in European aerosol increases ultimately have the same effect. While increasing greenhouse gas emissions act to strengthen the EASM via enhanced moisture transport, the two effects do not cancel each other out. The predominantly dynamical response to aerosol increases resulted in a weakening of the EASM in the late 20th century, and determined the spatial pattern of the observed precipitation anomalies, with flooding in southern China and drying in the north.
Concerns about air quality have resulted in large, rapid reductions in aerosol emissions over East Asia since 2010. Similar reductions may occur in other regions in the near future. Here, we use data from 10 models that participated in the Regional Aerosol Model Intercomparison Project (RAMIP) to quantify the EASM response to recent reductions in aerosol emissions over East Asia, continuing reductions over North America and Europe, and potential future reductions over South Asia and Africa and the Middle East. In addition to considering seasonal mean changes, we show the impact of regional aerosol reductions on temperature and precipitation extremes. We present an analysis of the mechanisms for the response of the EASM to both local and remote aerosol changes, assessing the relative roles of thermodynamic and dynamic changes, and show a moisture budget decomposition. The RAMIP dataset includes 10 models, and 10-member ensembles for all experiments, which enables us to identify robust physical responses to aerosol emission changes, and to identify where structural differences between the participating models lead to differences in near-future projections. The EASM strengthens in response to all aerosol reductions, although it is most strongly influenced by local aerosol changes.
How to cite: Wilcox, L., Bhandekar, A., Luo, F., Bollasina, M., Zhou, T., Samset, B., and Allen, R. and the The RAMIP modelling team: Strengthening of the East Asian Summer Monsoon in response to local and remote reductions in anthropogenic aerosol, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12557, https://doi.org/10.5194/egusphere-egu26-12557, 2026.
Atmospheric black carbon (BC) is known to strongly affect precipitation, primarily through rapid adjustments to emissions changes. Globally, studies have found a strong, negative correlation between BC induced atmospheric absorption and precipitation, meaning that the overall effect of BC emissions is a drying. A primary thermodynamic mechanism is that heating aloft, induced by shortwave absorption, competes with latent heat release from condensation, inhibiting droplet formation.
In some regions, however, the modelled precipitation response to an increase in BC emissions is positive. Previous studies indicate that this is a local effect, occurring in tropical regions and close to the source, but as yet there is no full mechanistic explanation.
Using a range of recent BC emission perturbation simulations from global climate models, we show that BC precipitation invigoration primarily occurs in monsoon regions, and is due to a dynamical "chimney effect", or elevated heat pump, overcoming the thermodynamic inhibition. This has previously been discussed for absorbing aerosols over India, but we find similar results across most monsoon regions. Here, there is a clear positive correlation between BC atmospheric absorption and precipitation change, that persists from rapid adjustments through to the full climate response to BC emissions. We also find a shift in precipitation patterns through the monsoon season, with monsoon onset on average coming earlier and becoming more intense.
These results have clear implications for the precipitation related climate hazards arising from BC emission changes, and therefore also for science based policy advice on BC mitigation measures.
How to cite: Samset, B. H., Joshi, M., Johansen, A. H., Staniaszek, Z., Allen, R. J., Stjern, C. W., and Wilcox, L. J.: Rapid adjustments to black carbon cause precipitation invigoration in monsoon regions, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6629, https://doi.org/10.5194/egusphere-egu26-6629, 2026.
Indian surface temperature has increased more slowly since 1970 than for most land regions at similar latitudes. Air pollution, which reflects sunlight and cools the surface, is widely considered a key contributor, yet the relative roles of aerosol emissions, natural variability, and other forcings remain uncertain, reducing confidence in projections of warming in India. Here, we combine observational temperature records with a new multi-model, multi-ensemble dataset from the Regional Aerosol Model Intercomparison Project (RAMIP) to isolate and quantify the influence of local and remote anthropogenic aerosol emissions on India’s past and future climate. We find that a cleanup of air pollution, necessary for health reasons, would likely turn India from a historical “warming hole” to a future “hotspot” where regional warming exceeds the global mean. This enhanced warming will substantially strengthen heat extremes. By linking climate projections with health impact assessments, however, we show that while aerosol mitigation would intensify heat-related risks, the net health benefits of cleaner air remain strongly positive.
How to cite: Stjern, C. W., Samset, B. H., Wilcox, L. J., Chowdhury, S., and Bhandekar, A.: From muted to rapid surface warming over India under changing aerosol emissions, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3371, https://doi.org/10.5194/egusphere-egu26-3371, 2026.
It is crucial to understand the drivers of extreme heat in India, as heatwave intensifies under a warming climate. This study examines the spatiotemporal evolution of heatwave hotspots across India and evaluates how aerosols and atmospheric dynamics loading influence their formation. A long-term archive of heatwave events from 1981 to 2020 is constructed using reanalysis-based daily maximum temperatures (Tmax). The results indicate a substantial rise in Tmax, with all-India warming of ~0.8 ± 0.30 °C between 1981–2000 and 2001–2020. We further examine how different large-scale conditions shape hotspot evolution by comparing periods with El Niño and non-El Niño periods. El Niño contributed to the rise of +0.68 °C in average Tmax, compared to +0.18 °C in non-El Niño years. Furthermore, heatwaves are identified using a percentile-based framework. A Heatwave Hotspot Index (HHI) is developed to quantify regional variations in heatwave-prone zones by integrating five key attributes: heatwave frequency, duration, intensity, Tmax anomaly, and number of hot days. Decadal assessments reveal a marked expansion and intensification of hotspots, especially in western, central and Peninsular India, suggesting an emerging southward shift in recent decades. Further, to assess aerosol influences, we analyze MODIS AOD, CALIPSO aerosol extinction profiles and aerosol types, and CERES radiative fluxes (2008–2020). The findings underscore contrasting aerosol–radiation interactions. Enhanced AOD and increased absorbing aerosol loading intensify surface warming across western and central India. In contrast, regions exhibiting relative cooling show elevated aerosol layers that enhance atmospheric absorption while reducing the amount of solar radiation reaching the surface. During heatwaves, large-scale phenomena like El Niño, along with aerosol radiative forcing patterns, explain how the aerosol buildup during extreme heat events exacerbates atmospheric heating. These findings show the importance of aerosol-radiation interaction in determining the severity and spatial patterns of heat extremes in India.
How to cite: banerjee, S. and Padmakumari, B.: Spatial Shift of Heatwave Hotspots in India: Unraveling the Roles of Aerosols, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-764, https://doi.org/10.5194/egusphere-egu26-764, 2026.
Rising global temperatures have intensified warm-season climate extremes over China in recent decades. This study examines changes in extreme temperature and precipitation during May–September and their links to greenhouse gas (GHG) increases and aerosol reductions, using observations, reanalysis data, and climate model simulations. During 2011–2023, daily maximum temperature (TXx), heatwave frequency, and heatwave mean duration show significant upward trends of 0.70 °C per decade, 3.77 days per decade, and 0.31 days per event per decade, respectively. Attribution analysis indicates that rising CO₂ concentrations contribute 43% ± 3% of the TXx increase, while declining aerosol optical depth, decreasing at 0.054 per decade due to improved air quality, accounts for 27% ± 3%. In eastern China, where aerosol reductions are strongest, aerosol decline explains up to 79% ± 10% of the TXx increase, amplifying heatwave intensity and persistence.
Extreme precipitation has also become more intense and frequent. A marked acceleration occurred around 2010, with the trend in accumulated extreme precipitation (R95pTOT) increasing from 2.88 mm per decade during 2000–2010 to 22.88 mm per decade during 2010–2023. This acceleration is largely driven by the reversal of aerosol trends associated with China’s clean air actions, which affect cloud microphysics and atmospheric dynamics and account for roughly half of the change in R95pTOT trends. Model projections suggest that continued aerosol reductions under carbon neutrality pathways will further intensify extreme precipitation, outweighing the effect of GHG forcing alone. These results highlight the critical role of both GHGs and aerosols in shaping recent and future warm-season climate extremes over China.
How to cite: Yang, Y.: Increasing weather extremes in China attributed to rising greenhouse gases and declining aerosols, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2042, https://doi.org/10.5194/egusphere-egu26-2042, 2026.
Synoptic fronts are most active in the mid-latitudes and are often associated with abrupt temperature changes and heavy precipitation. Over China, frontal activities play a crucial role in springtime rainfall, accounting for more than 40% of total precipitation in southern China. While previous studies have mainly focused on the influences of natural forcing and long-term climate change on frontal systems, the role of anthropogenic aerosols and their rapid impacts remain poorly understood. In this study, we investigate the fast response of frontal activity and associated precipitation over China to variations in anthropogenic aerosols. Observational analyses reveal that, concurrent with China’s sharp decline in anthropogenic emissions over the past two decades, frontal precipitation (FP) in spring has significantly increased over southern China, accompanied by a weak decrease in northern China. Simulations using the Community Earth System Model (CESM) indicate that the past anthropogenic aerosols reductions in China could lead to the similar dipole variation in FP, along with a general consistent change in front frequency and precipitation intensity. The changes in frontal activity are a result of the modified horizontal wet-bulb potential temperature gradient, which strengthens in the south whereas weakens in the north. Further analysis indicates that aerosol reductions lead to an immediate increase in surface solar radiation, disturbing near-surface temperature and its meridional gradient. The resulting circulation anomalies enhance convergence updraft over southern China, thus enhancing atmospheric moisture and favoring FP formation. Under China’s carbon neutrality target by 2060, continued aerosol mitigation is expected to further amplify the meridional displacement of FP, with opposing variations in front frequency and precipitation intensity between southern and northern China. Our results highlight the importance of anthropogenic aerosols in modulating synoptic-scale weather processes and provide new insights into intraseasonal precipitation variability under ongoing climate change and emission mitigation.
How to cite: Zhu, L. and Xue, L.: Enhanced Springtime Frontal Precipitation in Southern China Induced by Anthropogenic Aerosol Mitigation, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2945, https://doi.org/10.5194/egusphere-egu26-2945, 2026.
Prior research has established that higher aerosol concentrations can influence both precipitation formation and tropical cyclone intensity. As climate mitigation efforts advance, however, anthropogenic aerosol levels are projected to decline. This study investigates how such a decrease in aerosol concentration may alter tropical cyclone precipitation patterns, using Typhoons Haikui and Koinu as case studies. Simulations were conducted with the Weather Research and Forecasting (WRF) model employing the Thompson aerosol-aware microphysics scheme, in which water-friendly aerosol concentrations were reduced by two orders of magnitude. Results show that lower aerosol concentrations consistently expand the area of precipitation in both cyclones by enhancing the warm-rain process. Nevertheless, total precipitation amounts respond differently: they increase for Haikui but decrease for Koinu. This divergence is attributed to the relative dominance of warm-rain versus ice-phase microphysical processes and associated changes in upper-level convection.
How to cite: Mak, H. Y. L. and Shi, X.: The Variable Impact of Aerosol Reduction on Tropical Cyclone Precipitation, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3770, https://doi.org/10.5194/egusphere-egu26-3770, 2026.
Black carbon (BC) aerosols can affect both local and remote long-term climate, but whether they can induce remote changes at short-term timescales is unclear. Through analyses of observations and time-slice model simulations, this study shows that South Asian autumn BC aerosols can cause instant and delayed responses of surface air temperature over the Arctic and Eurasia. In autumn, higher BC loading over South Asia leads to decreased rainfall and tropospheric diabatic cooling there. This cooling can remotely excite an anomalous anticyclone over Europe that transports warm and moist air into the Arctic to precondition sea ice melting over the Barents-Kara Seas (BKS). The consequent decrease of sea ice cover (SIC) causes BKS warming through increased surface exchange fluxes, and the concurring anomalous anticyclone near the Ural Mountains induces surface cooling over Eurasia. This temperature anomaly pattern can persist into the ensuing winter due to the continued SIC decrease across seasons.
How to cite: Deng, J.: Instant and Delayed Effects of Autumn Black Carbon Aerosols Over South Asia on Arctic and Eurasian Surface Air Temperature, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1989, https://doi.org/10.5194/egusphere-egu26-1989, 2026.
Several papers in the last decades demonstrate the strong impact of aerosol emitted by ships in harbors, coastal regions, and also in the central Mediterranean Sea (e.g. Viana et al., 2014; Becagli et al., 2017).
The ship aerosol is characterized by high concentrations of sulphate and metals (V and Ni) and has been shown to affect the radiation field and to produce adverse health effects.
In the Mediterranean region, high sulphate levels (often exceeding 10 µg/m3), allowed to characterize this region as one of the areas worldwide strongly influenced by the negative radiative forcing induced by the sulphate.
A review of five ship aerosol modeling studies finds a mean radiative forcing at the top of the atmosphere of +0.12±0.03 W/m2 (Gettelman et al., 2024), essentially induced by changes in the cloud properties. Although the estimated radiative forcing expected from changes in ship aerosol is not large, its effect is highly nonlinear (i.e., if aerosols emitted into polluted air have much less effect on clouds than aerosols emitted into a pristine atmosphere), and the decreased ship emissions may have a large effect on Earth’s albedo.
This works aims to investigate the effect of the implementation of the International Maritime Organization (IMO) 2020 regulation leading to a decrease of sulfur concentration in the marine fuels down to 0.5%, on PM10 composition in central Mediterranean Sea. PM10 was sampled at Lampedusa by sequential aerosol sampler (Gemini Dadolab srl) equipped with PM10 and PTS sampling heads. PM10 was measured by gravimetry and analyzed for ions and metals content as reported in Becagli et al. (2012 and 2017). Several interesting conclusions cand be drawn from the comparison of sulphate, V, and Ni concentrations obtained before and after 2020.
The sulphate concentration has been observed to decrease by factor 2 in summer. The decrease is smaller than that observed in the eastern Mediterranean, where it was reduced by almost a factor of 4 since 90’s (Urdiales-Flores et al., 2023). This significant decrease in sulphate is considered as one of the main drivers of the rapid warming of the Mediterranean compared to the rest of the world (Urdiales-Flores et al., 2023).
A remarkably higher reduction in concentration is observed for V and Ni. The concentration of these metals decreases by a factor of about 5. Moreover, V ad Ni solubility shows a strong reduction with respect to data prior to 2020, becoming similar to that measured on crustal samples. Also, the V/Ni ratio of ship aerosol (soluble fraction) becomes close to 2, a value similar to that of mineral aerosol.
In previous studies (e.g., Becagli et al., 2012) values of V>8 ng/m3 coupled with the value of V/Ni ratio in the range 3-3.5 were used as a tracers for identifying ship-emitted particles. The present analysis shows that these criteria, are no more valid for present day measurements.
Viana et al. 2014. DOI: 10.1016/j.atmosenv.2014.03.046
Becagli et al. 2017. DOI: 10.5194/acp-17-2067-2017
Gettelman et al., 2024. DOI: 10.1029/2024gl109077.
Becagli et al. 2012. DOI: 10.5194/acp-12-3479-2012
Urdiales-Flores et al. 2023. DOI: 10.1038/s41612-023-00423-1
How to cite: Becagli, S., di Sarra, A., Di Iorio, T., Meloni, D., Monteleone, F., Quarratesi, G., Severi, M., Sferlazzo, D., and Traversi, R.: New evidence on the impact of ship emission in central Mediterranean Sea as a consequence of the sulfur reduction in heavy fuel oil, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6034, https://doi.org/10.5194/egusphere-egu26-6034, 2026.
Black carbon (BC) is a significant short-lived climate forcer due to its strong absorption of solar radiation. Quantifying its radiative effects is challenging due to the ageing-induced evolution of BC mixing state and its impact on BC light absorption. Open biomass burning in the form of wildfires is the dominant global source of BC. In the summer of 2025, Europe experienced record-high wildfire emissions, while Canada faced its second-highest annual total carbon emissions. During this period, southern France was impacted by both several major local wildfire outbreaks and long-range transport (LRT) of dense smoke plumes from Canadian wildfires. Our study assesses the BC properties measured in different plumes, allowing their characterization in both relatively fresh emissions from southern France and aged air masses transported from Canada. Observations were conducted using the Safire ATR42 research aircraft during SILEX, the first campaign of the European project EUBURN. A total of 15 flights were performed with simultaneous measurements of BC mass concentration using a Single Particle Soot-Photometer (SP2), CO, CO2 and CH4 concentration using a PICARRO gas analyser, and aerosol optical properties with a modified dual-wavelength airborne CAPS-PMSSA monitor and a Nephelometer. Additionally, geostationary satellite products and chemical-transport-model simulations performed using the FLEXPART and MOCAGE models were used as auxiliary data to support the aircraft measurements. Interestingly, within the wildfire plumes, aerosol particle number concentrations reached up to 17,040 #/cm3, accompanied by extinction coefficients at 520 nm as high as 275 Mm-1, highlighting the high aerosol load and pronounced aerosols-radiation interactions, potentially impacting the local to global radiative balance. The average values of the combustion source indicator (ΔBC/ΔCO) reflected a common signature attributed to biomass burning emissions (~7). Furthermore, the ATR42 in situ data with fuel type assessments revealed the dominance of flaming combustion, with modified combustion efficiency (ΔCO2/ΔCO2+ΔCO) values exceeding 0.9. The BC core size distribution exhibited a unimodal pattern, with peak diameters typically ranging between 184 to 210 nm. Ongoing analyses aim to examine the diversity of BC mixing states and the associated absorption enhancement in both local wildfire plumes from southern France and long-range transported from Canada.
How to cite: Velazquez-Garcia, A., Hubans, A., Paugam, R., Pelletier, S., Rodier, Q., Libois, Q., Borbon, A., Chiapello, I., Filippi, J.-B., Parent, G., Dominutti, P., Ruffault, J., Canonici, J., Boulanger, D., and Denjean, C.: Airborne characterization of black carbon properties in fresh and aged wildfire plumes over southern France, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17612, https://doi.org/10.5194/egusphere-egu26-17612, 2026.
Carbonaceous aerosols play a crucial role in climate forcing and the dynamics of the South Asian monsoon; however, their sources and deposition processes remain insufficiently understood. In this study, we used dual carbon isotopes (Δ¹⁴C, δ¹³C) to accurately trace water-insoluble carbon in rainwater samples collected from the Maldives Climate Observatory–Hanimaadhoo over four years, from 2019 to 2023.
Carbonaceous species in the rainwater exhibited pronounced seasonal contrasts. On average, black carbon concentrations were about five times higher in the winter monsoon than in the summer monsoon. In comparison, water-insoluble organic carbon was roughly twice as high in winter as in the summer monsoon. In our dataset, black carbon varied from 1.7 to 76.3 µg L⁻¹ during the winter monsoon, from 0.8 to 20.1 µg L⁻¹ during the summer monsoon, and from 1.0 to 29.0 µg L⁻¹ during the transitional periods. Water-insoluble organic carbon dominated the insoluble carbon pool, consistent with the notion that black carbon typically has a lower wet scavenging efficiency compared to more hydrophilic organic carbon fractions. Radiocarbon analysis indicated that biogenic sources, especially from biomass burning, are the primary contributors to water-insoluble carbon, accounting for approximately 59 ± 13% of the total. Notably, C3 plants alone contributed about 87% of this biomass signal. We observed distinct seasonal variations in these contributions; during the winter monsoon, we recorded higher biomass fractions, correlating with agricultural residue burning in the Indo-Gangetic Plain. In contrast, the summer monsoon saw an increase in fossil-fuel contributions, coinciding with heightened shipping activity and fossil-fuel combustion in the region.
The acidity of the rainwater (pH ranging from 4.2 to 6.9) varied with the origin of the air masses, underscoring the significant impact of anthropogenic activities during continental outflows. These findings provide valuable insights into the complex interactions between aerosols and monsoon systems, highlighting that deposition patterns are closely tied to local agricultural practices and energy consumption. Addressing the issues stemming from residue burning and shipping emissions could offer a sustainable pathway with potential co-benefits for climate resilience, ecosystems, and food security throughout the Indian Ocean region.
How to cite: Budhavant, K. B., Satheesh, S. K., and Gustafsson, Ö.: Carbonaceous Aerosol Deposition over the Northern Indian Ocean: Agricultural Burning, Shipping, and Sustainability Challenges, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6556, https://doi.org/10.5194/egusphere-egu26-6556, 2026.
In this investigation, we analyze the long-term determinants of aerosol pollution utilizing nationally accessible data from Pakistan on a provincial scale, spanning the years 2000 to 2022. This study employs aerosol optical depth (AOD) data derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) as a proxy indicator for particulate matter present in the atmosphere. It integrates satellite-derived environmental data with socio-economic and meteorological variables, including GDP per capita, levels of industrialization, population density, temperature, precipitation, and wind direction, to furnish a comprehensive assessment of both anthropogenic and natural influences on aerosol dispersion. Furthermore, the CS-ARDL model, accompanied by tests for cross-sectional dependence, slope heterogeneity, and cointegration, is utilized within the analysis. Additionally, it elucidates both long-term and short-term relationships among the variables under consideration. The findings of this research reveal that AOD is significantly influenced by economic growth, industrial output, and population density. This underscores the detrimental implications of Pakistan's developmental trajectory on environmental quality. Nevertheless, there exists a mitigating effect of variables such as precipitation and temperature, which serve as significant meteorological determinants of aerosol concentration. Conversely, wind direction emerges as a prominent spatial factor, potentially attributable to the translocation of pollutants across various regions. Furthermore, resistance analyses conducted on generalized method of moments (GMM) regression reveal that the findings exhibit a remarkable degree of consistency. This research addresses a notable deficiency in the empirical literature concerning the correlation between environmental degradation in developing nations and remote sensing data through the application of econometric modeling. Additionally, the study offers pertinent policy recommendations for decision-makers, as it underscores the imperative for regionally adaptive, seasonally responsive, and environmentally sustainable development and planning practices. In this context, it provides an evidence-based foundation for the formulation of substantiated air quality management strategies and sustainable development measures to be implemented throughout Pakistan.
How to cite: Imran, A.: Analyzing Temporal Aerosol Distribution over Pakistan Using MODIS Data and Their Socio-Economic Impacts, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-90, https://doi.org/10.5194/egusphere-egu26-90, 2026.
Sulfate aerosols exert a strong negative effective radiative forcing and remain a major source of uncertainty in regional climate projections. In South Asia, sustained elevated sulfate loadings are subject to intensified mitigation efforts. Such legislation could result in uncertain intensification of near-term warming through unmasking of net cooling aerosols. Robust source attribution is therefore needed to interpret past variability and to evaluate emission inventories used in climate and air-quality assessments.
In this study, we quantify anthropogenic versus natural contributions using the stable sulfur isotope composition (δ³⁴S) of aerosol sulfate (SO₄²⁻) measured at the Maldives Climate Observatory Hanimaadhoo (MCOH), a receptor site for the South Asian outflow. The analysis targets winter and summer monsoon air masses over 2006–2025 to sample contrasting transport regimes influencing MCOH.
Initial δ³⁴S-constrained apportionment indicates that wintertime sulfate is consistently dominated by anthropogenic sources (≈90–99%), whereas the summer monsoon shows a substantially larger spread in anthropogenic influence (≈47–88%). Ongoing work couples the isotopic constraints with FLEXPART transport footprints and state-of-the-art regionally-tuned emission inventories to resolve dominant upwind source regions and diagnose as well as improve agreement between inventory-based bottom-up estimates and in situ top-down observations. As the record is extended toward multi-decadal coverage, it will provide improved observational constraints on sulfate sources in the South Asian outflow and support evaluation and improvement of emission inventories, intrinsic to effective climate policy.
How to cite: Clarke, S., Remani, M., Rodiouchina, K., Holmstrand, H., Budhavant, K., Romson, J., Haslett, S., and Gustafsson, Ö.: Multi-decadal source apportionment of South Asia wintertime and summertime sulfate using δ³⁴S–SO₄²⁻ and emission-inventory-based model estimates, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17775, https://doi.org/10.5194/egusphere-egu26-17775, 2026.
This study on the planetary boundary: Atmospheric aerosol loading focuses on methods to develop high-resolution, chemically differentiable data, along with practical strategies to retain the boundary within limits. Planetary boundaries are a framework of nine interdependent processes that are altered by human activities. The boundaries define safe limits for these processes beyond which irreversible damage occurs to the Earth's ecosystem.
Atmospheric aerosol loading refers to the amount of aerosols readily available in the atmosphere. Aerosol Optical Depth is a measure of aerosols in the atmosphere through the amount of sunlight blocked from reaching the Earth's surface. High AOD accounts for low visibility, increased air pollution, and alters cloud formation, therefore disrupting monsoon patterns.
This planetary boundary quantifies the inter-hemispheric difference in atmospheric aerosol loading and defines a safe operating space to be less than 0.1. A significant decrease in this boundary value was observed in 2025 (0.063) compared to 2023 (0.076). However, regional exceedances have been observed throughout the year in Asia and Africa, with the regional boundary set at 0.25 (high risk), taking into consideration heavy monsoon areas. A decrease in atmospheric aerosols helps reduce air pollution and immediate health risks; however, the possibility of global warming increases due to the decrease in cooling aerosols and their impact on lowering the temperature.
The 2025 planetary health check takes into account the dual effect of aerosols (cooling & warming). The effective radiative forcing of aerosols affects the Earth's energy balance through scattering or absorbing sunlight. Aerosol-cloud interactions have a significant impact on the global net cooling or warming. Local variations and exceedances are primarily observed due to differences in aerosol type and emissions. Time series AOD data were obtained from the Copernicus Atmosphere Monitoring Service (CAMS) to analyse further and relate to surface-level pollution trends in the Indian Region. Further research needs well-consolidated data from observations and modelling to better understand local and global effects and consequences.
KEYWORDS: Atmospheric Aerosol Loading, Aerosol Optical Depth, Air Pollution.
How to cite: Pullepu, A. S. and Aggarwal, M.: Planetary Health Check: A Regional Evaluation of Aerosol Loading and Air Quality in Asia, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20228, https://doi.org/10.5194/egusphere-egu26-20228, 2026.
Aerosol-induced changes to the surface and atmospheric energy balance are crucial for understanding regional climate change, particularly in the Indian subcontinent, where carbonaceous aerosols contribute to atmospheric warming. However, our understanding of aerosol impacts lags that of greenhouse gases, partially due to a lack of primary observations regarding aerosol optical properties. This presentation synthesizes regional-scale and localized measurements of strongly absorbing carbonaceous aerosols to help constrain these gaps and identify key directions for future research. Analysis from the PAN-India COALESCE network, spanning nine regional sites, revealed significant spatiotemporal heterogeneity in aerosol absorption. Spectral measurements showed that brown carbon (BrC) contributes between 21% and 68% to near-UV absorption nationally. Despite this significant contribution, absorption by BrC particles is not routinely integrated into most climate models. While these national trends highlight a widespread underestimation of absorption, they also underscore the need for a more granular understanding of optical properties. Further intensive measurements were conducted at Rohtak, India, a representative urban-regional site in the highly polluted Indo-Gangetic Plain. Measurements revealed extreme aerosol loading (PM2.5 ~ 163 µ/m3) and strong absorption, with a single-scatter albedo (at 550 nm) of 0.7. Using a Mie inversion technique, we estimated the imaginary refractive index (a measure of aerosol absorption strength) to be between 0.076 and 0.145—values residing at the upper end of reported urban ranges globally. This high imaginary refractive index is attributed to black carbon and strongly absorbing BrC (mass absorption cross-sections at 550 nm of 1.9 m2 g-1) from primary combustion sources. Notably, the persistence of this absorption was linked to a dominance of low-volatility organic carbon fractions—termed dark brown carbon—that resists photo-bleaching. These particles exhibit absorption extending to longer, near-infrared wavelengths, warranting further investigation and inclusion in climate models. A systematic review of existing literature suggests that the detection method for BrC absorption significantly influences the reported magnitude and may potentially bias spectral signals, thereby complicating current model constraints.
These findings have direct implications for regional climate risk. The measured single-scatter albedo values are lower than those utilized in current climate simulations over South Asia. This systematic underestimation of absorption likely leads to biased projections of regional radiative forcing, surface dimming, and atmospheric heating rates. Such discrepancies could result in significant uncertainties regarding downstream meteorological extremes and climate risks. These risks can only be mitigated through improved measurements with more extensive spatiotemporal coverage to provide the constraints necessary for robust climate projections.
How to cite: Kapoor, T. S., Navinya, C., Phuleria, H. C., Venkataraman, C., and Chakrabarty, R. K.: Advancing Carbonaceous Aerosol Characterization in India to Improve Regional Climate Risk Assessment , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20632, https://doi.org/10.5194/egusphere-egu26-20632, 2026.
Posters virtual: Mon, 4 May, 14:00–18:00 | vPoster spot 5
EGU26-7763 | Posters virtual | VPS2
Rapid regional aerosol reductions drive near future intensification of the South Asian MonsoonMon, 04 May, 15:00–15:03 (CEST) vPoster spot 5
There is consensus that forcing due to Northern Hemispheric anthropogenic aerosols has played a significant role in the decline of South Asian monsoon precipitation since the mid-20th century. However, the future trajectory of regional aerosol emissions remains highly uncertain, particularly in light of potentially stricter air-quality regulations that could lead to reductions in aerosol loading across South and East Asia. Understanding how such changes may influence the near-term evolution of the monsoon is therefore critical. Here, we investigate the response of the South Asian summer monsoon to regional aerosol reductions using a suite of sensitivity experiments conducted with the IITM Earth System Model (IITM-ESMv2). Our simulations reveal a widespread intensification of monsoon precipitation over South and Southeast Asia following aerosol reductions. This response is driven by the combined effect of increasing greenhouse gas concentrations and declining absorbing aerosols over the subcontinent, which together enhance the land–sea thermal contrast. The strengthened thermal gradient promotes strengthened cross-equatorial low-level flow, leading to enhanced moisture transport and a sustained buildup of moisture across the monsoon region. The thermodynamic and dynamical changes favor widespread increases in precipitation. Our findings suggest that future air-pollution mitigation efforts across South and East Asia may play a critical role in shaping the near-future intensification of the monsoon, with important implications for regional hydroclimate over the coming decades.
How to cite: Dey Choudhury, A., Dhara, C., and Krishnan, R.: Rapid regional aerosol reductions drive near future intensification of the South Asian Monsoon , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7763, https://doi.org/10.5194/egusphere-egu26-7763, 2026.
