2025
Title
Plain Language Summary
Ouyang et al. (2025)
Climate change poses a severe global threat, demanding both mitigation and urgent adaptation actions. Effective adaptation depends on advanced, high-resolution models that integrate ecological and social factors while evaluating different adaptation scenarios. Local-scale models are especially valuable for producing detailed, context-specific insights that inform targeted adaptation strategies. This paper highlights the importance of accelerating the development of such models to strengthen local resilience and support effective responses to climate and urbanization challenges.
Vast and hidden urban methane emissions from the Russia–Ukraine war
Feng et al. (2025)
This study presents a satellite-based framework to assess methane emissions caused by the Russia–Ukraine war. Results show that warfare reverses the usual urban–rural emission pattern, with urban methane levels rising from 21% to as high as 588% of rural emissions under heavy attack. Civilian infrastructure, especially residential areas, contributes emissions comparable to those from military sites. The findings reveal a strong link between warfare, methane emissions, and urban vulnerability, emphasizing that peace is essential for meeting global climate goals.
This study examines turbulence non-stationarity in Beijing’s urban atmosphere, where classical turbulence theories based on ideal, stationary conditions often fail. Observations show that 52.41% of turbulence is non-stationary, leading to weakened vertical momentum transport and the breakdown of organized turbulence. Large-scale, non-turbulent motions are identified as the main drivers of this non-stationarity. Removing these large-scale components significantly reduces non-stationarity, offering insights for improving atmospheric boundary-layer modeling and parameterization.
Mainstreaming the local climate zone framework for climate-resilient cities
Yang et al. (2025)
The local climate zone framework is valuable for building climate-resilient cities but is limited in application. The limitation can be resolved by addressing three aspects: transdisciplinary dialog, global atlas construction, and cost-benefit assessment.
Penguin guano is an important source of climate-relevant aerosol particles in Antarctica
Boyer et al. (2025)
Gaseous ammonia, while influential in atmospheric processes, is critically underrepresented in atmospheric measurements. This limits our understanding of key climate-relevant processes, such as new particle formation, particularly in remote regions. Here, we present highly sensitive, online observations of gaseous ammonia from a coastal site in Antarctica, which allows us to constrain the mechanism of new particle formation in this region in unprecedented detail. Our observations show that penguin colonies are a large source of ammonia in coastal Antarctica, whereas ammonia originating from the Southern Ocean is, in comparison, negligible.
Validation of multi-model decadal simulations of present-day central European air-quality
Perez et al. (2025)
This study presents the first long-term validation of air quality models in Central Europe from 2010 to 2019 using WRF-Chem and CAMx simulations. Despite overall improvements in European air quality, pollutant levels like nitrogen dioxide and sulfur dioxide remain harmful to health. Model evaluations using the AirBase dataset show that simulations generally underestimate pollutant concentrations—except for ozone—likely due to inaccurate emission timing and excessive vertical mixing. These findings underscore the need for refined emissions data and model parameterizations to improve air quality assessments.
Savadkoohi et al. (2025)
The apportionment of equivalent black carbon (eBC) to combustion sources from liquid fuels (mainly fossil; eBCLF) and solid fuels (mainly non-fossil; eBCSF) is commonly performed using data from Aethalometer instruments (AE approach). This study evaluates the feasibility of using AE data to determine the absorption Ångström exponents (AAEs) for liquid fuels (AAELF) and solid fuels (AAESF), which are fundamental parameters in the AE approach.
GHOST: Globally Harmonised Observations in Space and Time, represents one of the biggest collection of harmonised measurements of atmospheric composition at the surface. In total, ~10 billion measurements from 1970-2025, of ~600 different components, from ~40 reporting networks, are compiled, parsed, and standardised. Components processed include gaseous species, total and speciated particulate matter, and aerosol optical properties.
Bardakov et al. (2024)
Isoprene and pinene are reactive organic gases emitted by plants. Deep convective clouds can transport them higher than 10 km altitude in the atmosphere. Using a computer model, we simulate their transport, chemistry, and the subsequent formation of nanometer-size particles in the cloud outflow. In the early morning, organic compounds containing nitrogen dominate the isoprene and pinene chemistry. We find that the reactions lead to the formation of nanoparticles, which can grow into condensation nuclei for cloud droplets. Our simulations show that the great abundance of nanoparticles observed high over the Amazon cannot be explained by pinene chemistry, as assumed previously.
Ciarelli et al. (2025)
Observational data collected in December 2014 at the base camp of Mount Everest, Nepal, indicated frequent new particle formation events of pure biogenic origin. Those events were speculated to be controlled by the along-valley winds forming in the valley connecting the Indo-Gangetic plain to the observational site, the Nepal Climate Observatory-Pyramid. The valley winds funnel highly oxygenated organic molecules of biogenic origin to higher elevations where they nucleate. The mechanism was referred to as “The Himalayan aerosol factory”. Its geographical extent and climate implications are currently unknown. In view of this, we conducted numerical chemical model simulations to corroborate the presence of the mechanism, and to quantify its geographical extent.
Meinander et al. (2025)
Climatic feedbacks and ecosystem impacts related to dust in the Arctic include direct radiative forcing (absorption and scattering), indirect radiative forcing (via clouds and cryosphere), semi-direct effects of dust on meteorological parameters, effects on atmospheric chemistry, as well as impacts on terrestrial, marine, freshwater, and cryospheric ecosystems. This review discusses our recent understanding on dust emissions and their long-range transport routes, deposition, and ecosystem effects in the Arctic. Furthermore, it demonstrates feedback mechanisms and interactions between climate change, atmospheric dust, and Arctic ecosystems.
Incomplete mass closure in atmospheric nanoparticle growth
Stolzenburg et al. (2025)
This study investigates why atmospheric nanoparticle growth often deviates from predictions based on gas-phase condensation of organic vapors. In the boreal forest, observed growth rates below 10 nm are accurately predicted only during spring, while warmer conditions show slower-than-expected growth. The results suggest that particle-phase reactions, phase separation, and diffusion limitations likely constrain growth under such conditions. These findings highlight key processes that limit nanoparticle formation and emphasize the need for more precise measurements of particle composition and hygroscopicity.
Navarro-Barbosa et al. (2025)
Brown carbon (BrC) absorbs ultraviolet (UV) and visible light, influencing climate. This study explores BrC’s imaginary refractive index (k) using data from 12 European sites. Residential emissions are a major organic aerosol (OA) source in winter, while secondary organic aerosol (SOA) dominates in summer. Source-specific k values were derived, improving model accuracy. The findings highlight BrC’s climate impact and emphasize source-specific constraints in atmospheric models.
New particle formation dynamics in the central Andes: contrasting urban and mountaintop environments
Aliaga et al. (2024)
This study examines new particle formation (NPF) in the Bolivian Andes at Chacaltaya mountain (CHC) and the urban El Alto–La Paz area (EAC). Days are clustered into four categories based on NPF intensity. Differences in particle size, precursor gases, and pollution levels are found. High NPF intensities increased Aitken mode particle concentrations at both sites, while volcanic influence selectively diminished NPF intensity at CHC but not EAC. This study highlights NPF dynamics in the Andes.
Influence of land cover change on atmospheric organic gases, aerosols, and radiative effects
Vella et al. (2025)
This study examines how land cover changes influence biogenic volatile organic compound (BVOC) emissions and atmospheric states. Using a coupled chemistry–climate–vegetation model, we compare present-day land cover (deforested for crops and grazing) with natural vegetation and an extreme reforestation scenario. We find that vegetation changes significantly impact global BVOC emissions and organic aerosols but have a relatively small effect on total aerosols, clouds, and radiative effects.
2024
Title
Plain Language Summary
Variability of aerosol particle concentrations from tyre and brake wear emissions in an urban area
Samland et al. (2024)
In this study, tyre and brake wear emissions are quantified applying a bottom-up model for the city of Hamburg in 2018. Their dispersion and contribution to total particulate matter (PM) concentrations are investigated with the urban scale chemistry transport model EPISODE-CityChem. The results of this study can be transferred to other large European cities with high traffic volumes and can help to understand the problem’s scope, as measurements rarely differentiate between particles caused by exhaust vs. non-exhaust emissions.
Liaskoni et al. (2024)
The impact of biogenic emissions of hydrocarbons from vegetation on ozone, as well as on overall oxidative capacity of air, is analyzed for central European cities for a present-day period using a chemistry transport model. Moreover, the analysis evaluates the partial role of urban vegetation in impacting all biogenic emissions. We found substantial increases in ozone due to these emissions, and about 10% of this increase is attributable to vegetation within urban areas.
PM2.5 Concentration Gap Reduction between Typical Urban and Nonurban China from 2000 to 2023
Guo et al. (2024)
Since 2013, stringent clean air initiatives have significantly improved air quality in China. Utilizing fine particulate matter (PM2.5) and its chemical composition data from 2000 to 2023, we observed a reduction in the disparity of PM2.5 concentrations between urban and non-urban areas. This reduction is linked to stricter emission controls in urban areas and the relocation of some emission sources to non-urban areas. However, the specific chemical constituents of PM2.5 and the driving factors behind these changes remain to be fully elucidated. This study analyzes the proportions of PM2.5 components in major cities such as Beijing, Shanghai, and Guangzhou and their surrounding non-urban areas.
Langendijk et al. (2025)
High-quality climate information tailored to cities’ needs assists decision makers to prepare for and adapt to climate change impacts, as well as to support the targeted transition towards climate resilient cities. Therefore, the WCRP CORDEX Flagship Pilot Study “URBan environments and Regional Climate Change (FPS URB-RCC)” brings together the urban climate modelling community and the RCM community and focuses on understanding the interactions between urban areas and regional climate change, with the help of coordinated experiments with an RCM ensemble having refined urban representations. This paper presents the FPS URB-RCC, its main aims, as well as the initial steps taken. The FPS URB-RCC advances urban climate projections and information to support evidence-based climate action towards climate resilient cities.
Unveiling the health impacts of air pollution transport in China
Ding et al. (2024)
The transport of atmospheric pollutants plays a pivotal role in regional air pollution, highlighting critical concerns over the unequal health outcomes that arise from such transport. The intensification of control measures necessitates a national perspective to comprehend the health impacts due to pollution transport. Our study establishes an integrated assessment framework that combines an emission-concentration response surface model with a health impact evaluation model to analyse the nationwide health impacts of PM2.5 and O3 pollution transport across China’s 31 provinces.
This study examines how limonene, a common compound in cleaning and personal care products, reacts with chlorine species generated during disinfection. Using quantum chemical and toxicology modeling, researchers identified key reaction pathways of chlorinated limonene peroxy radicals that drive the formation of secondary organic aerosol precursors. The results reveal that these reactions produce transformation products with higher respiratory, mutagenic, and irritation risks than limonene itself. These findings clarify the underlying chlorine-initiated chemistry of limonene and highlight potential health hazards from combined use of cleaners and disinfectants indoors.
The nitrous acid (HONO) budget was validated during a COVID-19 lockdown event. The main conclusions are (1) HONO concentrations showed a significant decrease from 0.97 to 0.53 ppb during lockdown; (2) vehicle emissions accounted for 53 % of nighttime sources, with the heterogeneous conversion of NO2 on ground surfaces more important than aerosol; and (3) the dominant daytime source shifted from the homogenous reaction between NO and OH (51 %) to nitrate photolysis (53 %) during lockdown.
Wollesen de Jonge et al. (2024)
Marine dimethyl sulfide (DMS) emissions are the dominant source of natural sulfur in the atmosphere. DMS oxidizes to produce low-volatility acids that potentially nucleate to form particles that may grow into climatically important cloud condensation nuclei (CCN). In this work, we utilize the chemistry transport model ADCHEM to demonstrate that DMS emissions are likely to contribute to the majority of CCN during the biological active period (May-August) at three different forest stations in the Nordic countries.
Pichelstorfer et al. (2024)
In the last few decades, atmospheric formation of secondary organic aerosols (SOA) has gained increasing attention due to their impact on air quality and climate. However, methods to predict their abundance are mainly empirical and may fail under real atmospheric conditions. In this work, a close-to-mechanistic approach allowing SOA quantification is presented, with a focus on a chain-like chemical reaction called “autoxidation”. A novel framework is employed to (a) describe the gas-phase chemistry, (b) predict the products’ molecular structures and (c) explore the contribution of autoxidation chemistry on SOA formation under various conditions.
FUME 2.0 – Flexible Universal processor for Modeling Emissions
Belda et al. (2024)
For modeling atmospheric chemistry, it is necessary to provide data on emissions of pollutants. These can come from various sources and in various forms, and preprocessing of the data to be ingestible by chemistry models can be quite challenging. We developed the FUME processor to use a database layer that internally transforms all input data into a rigid structure, facilitating further processing to allow for emission processing from the continental to the street scale.
Cloud response to co-condensation of water and organic vapors over the boreal forest
Heikkinen et al. (2024)
The organic vapor condensation with water vapor (co-condensation) in rising air below clouds is modeled in this work over the boreal forest where the air is rich in organic vapors. We show that the number of cloud droplets can increase by 20 % if considering co-condensation. The enhancements are even larger if the air contains many small, naturally produced aerosol particles. Such conditions are most frequently met in spring in the boreal forest.
Bartík et al. (2024)
The presented study deals with the attribution of fine particulate matter (PM2.5) concentrations to anthropogenic emissions over Central Europe using regional-scale models. It calculates the present-day contributions of different emissions sectors to concentrations of PM2.5 and its secondary components. Moreover, the study investigates the effect of chemical non-linearities by using multiple source attribution methods and secondary organic aerosol calculation methods.
Savenets et al. (2024)
Wildfires frequently occur in Ukraine during agricultural open-burning seasons in spring and autumn. High aerosol concentrations from fire emissions can significantly affect meteorological processes via direct and indirect aerosol effects. To study these impacts, we selected a severe wildfire episode from April 2020 in the Chornobyl Exclusion Zone (CEZ) and its surrounding area as a case study.
Mahura et al. (2024)
The Pan-Eurasian Experiment Modelling Platform (PEEX-MP) is one of the key blocks of the PEEX Research Programme. The PEEX MP has more than 30 models and is directed towards seamless environmental prediction. The main focus area is the Arctic-boreal regions and China. The models used in PEEX-MP cover several main components of the Earth’s system, such as the atmosphere, hydrosphere, pedosphere and biosphere, and resolve the physical-chemical-biological processes at different spatial and temporal scales and resolutions. This paper introduces and discusses PEEX MP multi-scale modelling concept for the Earth system, online integrated, forward/inverse, and socioeconomical modelling, and other approaches with a particular focus on applications in the PEEX geographical domain.
Impact of Biomass Burning on Arctic Aerosol Composition
Gramlich et al. (2024)
Emissions from biomass burning (BB) occurring at midlatitudes can reach the Arctic, where they influence the remote aerosol population. By using measurements of levoglucosan and black carbon, we identify seven BB events reaching Svalbard in 2020. We find that most of the BB events are significantly different to the rest of the year (nonevents) for most of the chemical and physical properties.
Oxidation Mechanism and Toxicity Evolution of Linalool, a Typical Indoor Volatile Chemical Product
Fu et al. (2024)
Linalool, a high-reactivity volatile chemical product (VCP) commonly found in cleaning products and disinfectants, is increasingly recognized as an emerging contaminant, especially in indoor air. Understanding the gas-phase oxidation mechanism of linalool is crucial for assessing its impact on atmospheric chemistry and human health. Using quantum chemical calculations and computational toxicology simulations, we investigated the atmospheric transformation and toxicity evolution of linalool under low and high NO/HO2· levels, representing indoor and outdoor environments.
Kulmala et al. (2024)
Atmospheric new particle formation (NPF), together with secondary production of particulate matter in the atmosphere, dominates aerosol particle number concentrations and sub-micron particle mass loads in many environments globally. In this opinion paper, we describe the paradigm shift to understand NPF in a continuous way instead of using traditional binary event–non-event analysis.
Malley et al. (2024)
Future changes in exposure to risk factors should impact mortality rates and population. However, studies commonly use mortality rates and population projections developed exogenously to the health impact assessment model used to quantify future health burdens attributable to environmental risks that are therefore invariant to projected exposure levels. This impacts the robustness of many future health burden estimates for environmental risk factors. This work describes an alternative methodology that more consistently represents the interaction between risk factor exposure, population and mortality rates, using ambient particulate air pollution (PM2.5) as a case study.
Savadkoohi et al. (2024)
A reliable determination of equivalent black carbon (eBC) mass concentrations derived from filter absorption photometers (FAPs) measurements depends on the appropriate quantification of the mass absorption cross-section (MAC) for converting the absorption coefficient (babs) to eBC. This study investigates the spatial–temporal variability of the MAC obtained from simultaneous elemental carbon (EC) and babs measurements performed at 22 sites.
Constructing transferable and interpretable machine learning models for black carbon concentrations
Fung et al. (2024)
Machine learning (ML) models have been studied extensively to serve as virtual sensors to complement the reference instruments. This study evaluates and compares three white-box (WB) and four black-box (BB) ML models to estimate black carbon concentrations, with the focus to show their transferability and interpretability. We train the models with the long-term air pollutant and weather measurements in Barcelona urban background site, and test them in other European urban and traffic sites.
Heslin-Rees (2024)
Light-absorbing atmospheric particles (e.g. black carbon – BC) exert a warming effect on the Arctic climate. We show that the amount of particle light absorption decreased from 2002 to 2023. We conclude that in addition to reductions in emissions of BC, wet removal plays a role in the long-term reduction of BC in the Arctic, given the increase in surface precipitation experienced by air masses arriving at the site. The potential impact of biomass burning events is shown to have increased.
Akritidis et al. (2024)
Long-term exposure to ambient ozone (O3) is associated with excess respiratory mortality. Pollution emissions, demographic, and climate changes are expected to drive future ozone-related mortality. Here, we assess global mortality attributable to ozone according to an Intergovernmental Panel on Climate Change (IPCC) Shared Socioeconomic Pathway (SSP) scenario applied in Coupled Model Intercomparison Project Phase 6 (CMIP6) models, projecting a temperature increase of about 3.6 °C by the end of the century.
Blichner et al. (2024)
Natural aerosol feedbacks are expected to become more important in the future, as anthropogenic aerosol emissions decrease due to air quality policy. One such feedback is initiated by the increase in biogenic volatile organic compound (BVOC) emissions with higher temperatures, leading to higher secondary organic aerosol (SOA) production and a cooling of the surface via impacts on cloud radiative properties. Motivated by the considerable spread in feedback strength in Earth System Models (ESMs), we here use two long-term observational datasets from boreal and tropical forests, together with satellite data, for a process-based evaluation of the BVOC-aerosol-cloud feedback in four ESMs.
Ciarelli et al. (2024)
The terrestrial ecosystem releases large quantities of biogenic gases in the Earth’s Atmosphere. These gases can effectively be converted into so-called biogenic aerosol particles and, eventually, affect the Earth’s climate. Climate prediction varies greatly depending on how these processes are represented in model simulations. In this study, we present a detailed model evaluation analysis aimed at understanding the main source of uncertainty in predicting the formation of biogenic aerosols.
2023
Title
Plain Language Summary
Casqero-Vera et al. (2023)
Aliaga et al. (2023)
Kulmala et al. (2023)
This is the first study of the effect of mineral dust on the inhibition/promotion of new particle formation (NPF) events in different dust-influenced areas. Unexpectedly, the research shows that the occurrence of NPF events is highly frequent during mineral dust outbreaks, occurring even during extreme dust outbreaks. It also shows that the occurrence of NPF events during mineral dust outbreaks significantly affects the potential cloud condensation nuclei budget.
We introduce a novel method for evaluating days when small particles are formed in the atmosphere. Instead of the traditional binary division between event and non-event days, our method, known as “nano ranking analysis”, provides a continuous, non-categorical metric for each day. By utilizing data from Hyytiälä, Finland, we show that our approach effectively quantifies these events. This innovative method paves the way for a deeper understanding of the factors influencing particle formation.
To be able to meet global grand challenges, we need comprehensive open data with proper metadata. In this opinion paper, we describe the SMEAR (Station for Measuring Earth surface – Atmosphere Relations) concept and include several examples (cases), such as new particle formation and growth, feedback loops and the effect of COVID-19, and what has been learned from these investigations. The future needs and the potential of comprehensive observations of the environment are summarized.
Zhou et al. (2023)
A Green Sahara with enhanced rainfall and larger vegetation cover existed in northern Africa about 6000 years ago. Biosphere–atmosphere interactions are found to be critical to explaining this wet period. Based on modeled vegetation reconstruction data, dust emissions and aerosol formation are simulated, which are key factors in biosphere–atmosphere interactions. The results also provide a benchmark of aerosol climatology for future paleo-climate simulation experiments.
Sink, Source or Something In-Between? Net Effects of Precipitation on Aerosol Particle Populations
Khadir et al. (2023)
Atmospheric aerosols, clouds, and precipitation play a significant role in Earth’s temperature regulation and air quality. While clouds and precipitation help remove particles from the atmosphere, recent research suggests rain could also introduce new particles. However, the extent of this particle source and its impact on climate are still unknown. This study analyzes years of observational data from clean environments and discovered that after precipitation, new particles were sometimes added to the surface atmosphere. The findings highlight the importance of considering how clouds and rain recycle particles when studying air quality and climate.
Okuljar et al. (2023)
Highly oxygenated organic molecules (HOMs) form secondary organic aerosol that affects air quality and health. This study demonstrates that in a moderately polluted city with abundant vegetation, the composition of HOMs is largely controlled by the effect of NOx on the biogenic volatile organic compound oxidation. Comparing the results from two nearby stations, the results show that HOM composition and formation pathways can change considerably within small distances in urban environments.
Tang et al. (2023)
Strong, ongoing high-latitude warming is causing changes to vegetation composition and plant productivity, modifying plant emissions of biogenic volatile organic compounds (BVOCs). In the sparsely populated high latitudes with clean background air, climate feedback resulting from BVOCs as precursors of atmospheric aerosols could be more important than elsewhere on the globe. Here, we quantitatively assess changes in vegetation composition, BVOC emissions, and secondary organic aerosol (SOA) formation under different climate scenarios.
Things are not always as they first seem in ambient aerosol measurements. Observations of decreasing particle sizes are often interpreted as resulting from particle evaporation. This paper shows that such observations can counter-intuitively be explained by particles that are constantly growing in size. This requires one to account for the previous movements of the observed air. Our explanation implies a larger number of larger particles, meaning more significant effects of aerosols on climate and health.
Toward a versatile spaceborne architecture for immediate monitoring of the global methane pledge
Wang et al. (2023)
Substantial advances have been made in recent years toward detecting and quantifying methane super-emitters from space. However, such advances have rarely been expanded to measure the global methane pledge because large-scale swaths and high-resolution sampling have not been coordinated. Here we present a versatile spaceborne architecture that can juggle planet-scale and plant-level methane retrievals, challenge official emission reports, and remain relevant for stereoscopic measurements.
Bornstein and Baklanov (2023)
The paper summarizes many of the scientific achievements of Professor Sergej S. Zilitinkevich (1936–2021). It first focuses on his basic and applied atmospheric boundary layer research contributions. It then reviews their applications within research and operational numerical weather prediction and air quality modeling, showing their contribution to solving modeling problems related to extremely-stable and -unstable boundary layers.
Widespread detection of chlorine oxyacids in the Arctic atmosphere
Tham et al. (2023)
Chlorine radicals are strong atmospheric oxidants known to play an important role in the depletion of surface ozone and the degradation of methane in the Arctic troposphere. Initial oxidation processes of chlorine produce chlorine oxides, and it has been speculated that the final oxidation steps lead to the formation of chloric (HClO3) and perchloric (HClO4) acids, although these two species have not been detected in the atmosphere. Here, we present atmospheric observations of gas-phase HClO3 and HClO4.
Kulmala et al. (2023)
This paper highlights turbulence as a central process governing the transport of material and energy in the atmosphere and shaping numerous chemical and physical interactions. Turbulence drives concentration fluctuations that influence deposition, chemical reactions, aerosol formation, and boundary-layer meteorology. Understanding its mechanisms and feedbacks with atmospheric chemistry and aerosol dynamics is essential for addressing both air pollution and climate change. The study outlines how insights into turbulence can bridge fundamental research with practical solutions for mitigating and adapting to climate impacts.