Beyond discrete stratocumulus regimes: a ternary continuum of morphology reveals within-regime variability in cloud susceptibilities Atmospheric Chemistry and Physics DOI 10.5194/acp-26-7193-2026 27 May 2026 We introduce a new way to describe marine low cloud morphologies as a continuous range rather than discrete types. Using this approach, we show that cloud brightness responses to changes in droplet concentrations vary strongly across cloud morphologies, but the overall effect is small. This suggests that marine cloud brightening may rely more on increasing cloud cover than on making existing clouds brighter. Read more
Evaluation of stratospheric transport in three generations of Chemistry-Climate Models Atmospheric Chemistry and Physics DOI 10.5194/acp-26-5249-2026 21 April 2026 Accurate representation of stratospheric transport in Chemistry-Climate Models is essential for reliable climate projections. This study evaluates three generations of models using observational data and reanalyses, identifying persistent biases and their potential causes. Some biases persist or even worsen in newer models. These findings highlight key limitations and inform efforts to improve models and advance understanding through process-based studies and enhanced observations. Read more
Drivers and implications of declining fossil fuel CO2 concentrations in Chinese cities revealed by radiocarbon measurements Atmospheric Chemistry and Physics DOI 10.5194/acp-26-5085-2026 16 April 2026 Our study indicates fossil fuel CO2 (CO2ff) reductions in Chinese megacities via atmospheric Δ(14CO2) and δ(13CO2) measurements, driven by coal-to-gas transitions and combustion efficiency improvement. The 24-year record show steeper declined urban RCO/CO2ff ratios than inventory estimates, implying underestimation of efficiency improvements and CO reductions. Integrating top-down observations with inventories is critical to track policy-driven emission shifts and optimize co-benefit strategies. Read more
Widespread occurrence of large molecular methylsiloxanes in ambient aerosols Atmospheric Chemistry and Physics DOI 10.5194/acp-26-5005-2026 16 April 2026 We identify a previously unrecognized class of synthetic organic compounds, large molecular methylsiloxanes, in ambient aerosols across diverse environments in three countries. These compounds are present at substantial levels, primarily originating from traffic emissions related to engine lubrication. Their high abundance and significant daily human exposure suggest potential, yet still poorly understood, implications for both health and climate. Read more
Quiet New Particle Formation is a significant aerosol source in the Amazon boundary layer Atmospheric Chemistry and Physics DOI 10.5194/acp-26-4885-2026 14 April 2026 Aerosols are tiny particles that help clouds form and influence the climate. In the Amazon, clear events of new aerosol particle formation are rare, making it difficult to explain their origin. Using ten years of measurements, we discovered a subtle but frequent process called Quiet New Particle Formation. This hidden mechanism slowly produces and grows small particles and is responsible for nearly half of the smallest aerosols observed during the wet season. Read more
Emerging low-cloud feedback and adjustment in global satellite observations Atmospheric Chemistry and Physics DOI 10.5194/acp-26-4153-2026 26 March 2026 Recent decades have seen a marked decrease in global low-level cloud cover, leading to more sunlight heating the Earth. This trend is poorly understood, raising the concern that clouds may amplify global warming more than previously thought. We show that the cloud decrease is mostly caused by human forcing on climate, and that it agrees with previous estimates of how clouds respond to decreasing aerosol pollution, increasing greenhouse gas concentration, and their effects on global temperature. Read more
A survey of snow growth signatures from tropics to Antarctica using triple-frequency radar observations Atmospheric Chemistry and Physics DOI 10.5194/acp-26-1249-2026 27 January 2026 Despite the increasing complexity of snow microphysics schemes employed in numerical models, whether the dominant snow microphysical process is reasonably identified remains an open question. This study using unprecedented triple-frequency radar observations for the first time unravels the key snow growth processes over diverse geographies. The unique cross-continental datasets from triple-frequency campaigns shed new insights for model evaluation and future satellite missions. Read more
Impact on cloud properties of reduced-sulphur shipping fuel in the Eastern North Atlantic Atmospheric Chemistry and Physics DOI 10.5194/acp-26-1041-2026 26 January 2026 The amount of sunlight reflected by marine boundary layer clouds in the Eastern North Atlantic does not change due to a decrease in aerosol caused by reduced sulphur in shipping fuel because adjustments to liquid water path offset the decease in cloud droplet number concentration. Read more
Emerging Mineral Dust Source in ’A’ą̈y Chù’ Valley, Yukon, Canada Poses Potential Health Risk via Exposure to Metal and Metalloids Enriched in PM10 and PM2.5 Size Fractions Atmospheric Chemistry and Physics DOI 10.5194/acp-26-1321-2026 26 January 2026 Glacial sediment of the ’A’ą̈y Chù’ Valley in Yukon, Canada is exposed to strong winds, and consequently, has become a significant mineral dust source. Mineral dust is known to have an impact on human health, partly due to various metals it contains, with the size of the particles also being an important factor. The goal of this study was to determine the concentration of various metals in the dust, how this relates to dust size, and whether air quality standards were surpassed. Read more
Injection near the stratopause mitigates the stratospheric side effects of sulfur-based climate intervention Atmospheric Chemistry and Physics DOI 10.5194/acp-25-18449-2025 18 December 2025 Injecting sulfur dioxide at 50 km – near the stratopause – offers a far safer and more effective climate intervention than conventional 25 km injection. Rapid downward–poleward transport distributes aerosols across 20–30 km, halving tropical stratospheric warming, reducing ozone recovery delays from decades to about 5 years, and enhancing global and polar cooling by over 20 %, while better preserving Arctic sea ice. Read more