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# CERTAINTY

Cloud-aERosol inTeractions & their impActs IN The earth sYstem

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- [Home](https://certainty-aci.eu/) - CERTAINTYCloud-aERosol inTeractions & their impActs IN The earth sYstem The recent decade has seen an unprecedented acceleration in climate change and related weather extremes. Significant questions remain regarding how aerosol-cloud-radiation interactions control and modify these events. CERTAINTY aims to deliver the knowledge and models that provide improved confidence and representation of the role of cloud–aerosol-radiation
- [Publications](https://certainty-aci.eu/publications/) - PUBLICATIONS Process evaluation suggests models misrepresent the precipitation-driven replenishment of cloud condensation nuclei Blichner, S. M., Khadir, T., Talvinen, S., Artaxo, P., Heikkinen, L., Kokkola, H., Krejci, R., Irfan, M., van Noije, T., Petäjä, T., Pöhlker, C., Seland, Ø., Svenhag, C., Vartiainen, A., and Riipinen, I Atmos. Chem. Phys., 26, 11281–11307, https://doi.org/10.5194/acp-26-11281-2026 Long-term trends in
- [Events](https://certainty-aci.eu/events/) - PAST EVENTS Webinar: New aerosol and surface reflectance products from novel satellite observations and their synergies Speaker: Oleg Dubovik (CNRS, Univ. of Lille)Moderator: Anna Gialitaki (NOA)18 June 2026 at 14:00 CEST EGU, 3-8 May 2026 in Vienna Session AS3.7 "Clouds, Aerosols, Radiation & Precipitation"and many more CERTAINTY Annual meeting, 17-20 March 2026 - by invitation
- [News](https://certainty-aci.eu/news/) - NEWS Webinar: New aerosol and surface reflectance products from novel satellite observations and their synergies Oleg Dubovik (CNRS, Univ. of Lille)Moderator: Anna Gialitaki (NOA)18 June 2026 at 14:00 CEST June 2026 Newsletter Desert dust warming exceeds model estimates A recent study by Kok, J.F. et al. investigates how desert dust affects Earth’s climate through interactions with
- [Videos](https://certainty-aci.eu/videos/) - Videos [Video] What scientists can learn by flying through clouds Georgios Dekoutsidis from the CERTAINTY project explains how he studies complex atmospheric processes using data collected during the PERCUSION campaign. [Video] These tiny particles control how clouds freeze Despite their tiny size and small number, ice nucleating particules have a huge impact on global weather
- [EC ESA Aerosol Cloud Cluster](https://certainty-aci.eu/ec-esa-aerosol-cloud-cluster/) - Joint policy brief Joint publications Raatikainen, T., Calderón, S., Järvinen, E., Prank, M., and Romakkaniemi, S. Can rime splintering explain the ice production in Arctic mixed-phase clouds? Atmos. Chem. Phys., 26, 5019–5038, https://doi.org/10.5194/acp-26-5019-2026 Costa-Surós, M., Gonçalves Ageitos, M., Chatziparaschos, M., Georgakaki, P., Thomas, M. A., Montané Pinto, G., Myriokefalitakis, S., van Noije, T., Le Sager, P.,
- [The project](https://certainty-aci.eu/about/) - All videos Key target ACI uncertainties CERTAINTY aims to train the next generation of multidisciplinary, diverse ACI scientists. To improve our predictions of climate sensitivity and future climate response, CERTAINTY will organize interdisciplinary courses/workshops on topics relevant to achieve the goal of improving understanding and constraining the role of ACI/ARI. CERTAINTY partners are leading the
- [Desert dust warming exceeds model estimates](https://certainty-aci.eu/desert-dust-warming-exceeds-model-estimates/) - Desert dust warming exceeds model estimates A recent study by Kok, J.F. et al. investigates how desert dust affects Earth’s climate through interactions with longwave radiation. Using a model based on observational data, the authors estimate that dust produces a global longwave radiative warming effect* of +0.25 ± 0.06 W m⁻², nearly twice the value represented in
- [TEAM](https://certainty-aci.eu/team/) - CONsortium 18 partners from 10 countries Jennie ThomasIGE/CNRSProject coordinator Harri KokkolaFMIScientific coordinator Hugh CoeUoMWP1 lead Silke GrossDLRWP1 lead Angela BenedettiECMWF WP2 lead Ed GryspeerdtICLWP2 lead Carlos Pérez García-Pando BSC WP3 lead Zamin KanjiETHZWP3 lead Annele VirtanenUEF WP4 lead Ilona RiipinenSUWP4 lead Moa SporreLUWP5 lead Twan van NoijeKNMIWP5 lead Anca HienolaFMIWP6 lead Bjorn StevensMPI-M Eleni MarinouNOA
- [Discover our progress: interactive overview of results](https://certainty-aci.eu/discover-our-progress-interactive-overview-of-results/) - Discover our progress: interactive overview of results To explore our progress on aerosol–cloud interactions, simply move your cursor over the figure. A pop-up window will appear over each element (warm clouds, aerosols, precipitation, etc.), providing an explanation along with links to the relevant publications.
- [[Video] Our climate is surprisingly sensitive to these tiny particles](https://certainty-aci.eu/video-our-climate-is-surprisingly-sensitive-to-these-tiny-particles/) - Our climate is surprisingly sensitive to these tiny particles What happens to our climate if the ingredients of clouds change? That question is asked in a recent paper written by CERTAINTY scientists. Aerosols (small particles emitted by natural and human sources) can cool the climate by changing how clouds form and behave, partly counteracting the
- [Distinct effects of low- and high-altitude clouds on transpiration](https://certainty-aci.eu/distinct-effects-of-low-and-high-altitude-clouds-on-transpiration/) - Distinct effects of low- and high-altitude clouds on transpiration Cloud characteristics, especially altitude, play a key role in regulating forest transpiration. Using long-term sap flow and cloud observations from European boreal and temperate forests, a recent study by Talvinen et al. shows that not all clouds influence trees in the same way.Low-altitude clouds tend to suppress
- [EGU26](https://certainty-aci.eu/egu26/) - EGU26 Join CERTAINTY researchers in Vienna at EGU. CERTAINTY co-organized sessions: Clouds, Aerosols, Radiation and Precipitation Thu, 07 May, 08:30–12:25 (CEST), 14:00–17:55 (CEST) - Room F2​Convener: Anna Possner | Co-conveners: Hailing Jia, Harri Kokkola, Montserrat Costa Surós, Romanos Foskinis Bridging Disciplines: Interactions Between Polar Aerosols, Clouds, Sea Ice, and Oceans in a Changing Climate Mon, 04 May, 16:15–18:00 (CEST)
- [Contribution to recent review papers on polar aerosol processes](https://certainty-aci.eu/contribution-to-recent-review-papers-on-polar-aerosol-processes/) - Contribution to recent review papers on polar aerosol processes Two recent studies co-authored by CERTAINTY team members that have participated and contributed to the Cice2Clouds SCOR working group have been published. These papers and the working group are improving our understanding of how the polar oceans, sea ice, and the associated atmospheric particles form and behave in polar regions
- [What is the EC-ESA Aerosol Cloud Cluster](https://certainty-aci.eu/what-is-the-ec-esa-aerosol-cloud-cluster/) - What is the EC-ESA Aerosol Cloud Cluster? The EC-ESA Aerosol Cloud Cluster addresses the biggest uncertainty in regional climate prediction: aerosol-cloud interactions. These interactions affect sunlight, clouds, and rainfall, and respond quickly to emission changes, making them crucial for effective climate action.The cluster unites Europe’s top experts, linking EU-funded projects CleanCloud and CERTAINTY with ESA initiatives
- [Aerosols, Clouds, and Climate in 2 Minutes](https://certainty-aci.eu/aerosols-clouds-and-climate-in-2-minutes/) - Aerosols, clouds, and climate in 2 minutes Explore how clouds form, the crucial role aerosols play in weather and climate, and why understanding these tiny particles remains one of society’s biggest scientific challenges.
- [ Why do we need better weather and climate projections?](https://certainty-aci.eu/why-do-we-need-better-weather-and-climate-projections/) - Why do we need better weather and climate projections? So we can make better decisions today for the world of tomorrow. We plan cities, manage agriculture, build infrastructure, design energy systems, and protect communities based on what we expect the climate and weather to be like in 5, 10, or even 50 years.Better projections mean
- [From Canada to India: the far-reaching impact of 2023’s wildfire smoke](https://certainty-aci.eu/from-canada-to-india-the-far-reaching-impact-of-2023s-wildfire-smoke/) - From Canada to India: the far-reaching impact of 2023’s wildfire smoke In August 2023, India experienced its driest August since records began, with a 36% rainfall deficit. A new study by Roșu et al. suggests that the unprecedented Canadian wildfires* of the same year may have contributed to this anomaly. The smoke from these fires cooled the
- [Influence of secondary ice formation on tropical deep convective clouds ](https://certainty-aci.eu/influence-of-secondary-ice-formation-on-tropical-deep-convective-clouds/) - Influence of secondary ice formation on tropical deep convective clouds Sun et al. looked at how secondary ice production (SIP) affects strong tropical storm clouds. SIP means that new ice crystals are created from existing ice particles inside a cloud, not just from the first freezing event. The researchers added different SIP processes into a weather model
- [How Saharan dust influences the marine boundary layer over the Atlantic](https://certainty-aci.eu/how-saharan-dust-influences-the-marine-boundary-layer-over-the-atlantic/) - How Saharan dust influences the marine boundary layer over the Atlantic A recent study by Tsikoudi et al. investigates the dynamics of the atmospheric boundary layer (the lowest part of the atmosphere) over the Atlantic Ocean near Cabo Verde, and how it is affected by dust transported from the Sahara. The boundary layer plays a key role in
- [Improving estimates of how aerosols influence cloud droplet formation](https://certainty-aci.eu/improving-estimates-of-how-aerosols-influence-cloud-droplet-formation/) - Improving estimates of how aerosols influence cloud droplet formation Clouds form when aerosols take up water and become droplets. Knowing how many droplets form from a given number of aerosols is important for predicting weather and climate, but this is difficult to measure because many factors affect droplet formation. A new study by Irfan et
- [News: Clouds formation are highly sensitive to aerosols change](https://certainty-aci.eu/news-clouds-formation-are-highly-sensitive-to-aerosols-change/) - Clouds formation is highly sensitive to aerosols change A new study published in Nature Geoscience reveals that clouds are more sensitive to aerosol changes than previously thought. Observations from ACTRIS stations in Svalbard and Finland provided long-term data to better understand how aerosols influence cloud properties. The findings indicate that fine particle emissions from human activities have contributed
- [Air pollution impacts weather and climate, but just how much?](https://certainty-aci.eu/air-pollution-impacts-weather-and-climate-but-just-how-much/) - Air pollution impacts weather and climate, but just how much? Europe’s leading scientists on aerosol and clouds have joined forces to uncover a dominant source of uncertainty in climate science. The Earth is warming more rapidly than before, and extreme weather events are becoming more frequent and more intense. While global warming is mainly driven
- [Policy brief - Addressing aerosol-cloud interactions for climate resilience](https://certainty-aci.eu/policy-brief-addressing-aerosol-cloud-interactions-for-climate-resilience/) - EC-ESA Aerosol Cloud Cluster Policy Brief 2026Download
- [Work Package Structure](https://certainty-aci.eu/work-package-structure/) - Work package Structure WP1: Fundamental knowledge of cloud-aerosol processes: from the cloud to regional scale Leads: Hugh Coe (UoM), Silke Gross (DLR) WP2: Fundamental knowledge of cloud-aerosol processes: from the regional to global scale Leads: Angela Benedetti (ECMWF), Ed Gryspeerdt (ICL) WP3: Improved parameterizations of cloud-aerosol interactions Leads: Carlos Pérez García-Pando (BSC), Zamin Kanji (ETH
- [News: How freezing raindrops create extra ice in clouds](https://certainty-aci.eu/news-how-freezing-raindrops-create-extra-ice-in-clouds/) - How freezing raindrops create extra ice in clouds Mixed-phase clouds contain both water droplets and ice crystals at the same time. They are common and play an important role in the climate system. To make reliable predictions about Earth’s energy balance, precipitation patterns, and future warming, weather and climate models need to represent these clouds
- [News: Europe’s polar research: a united call for stronger support](https://certainty-aci.eu/news-europes-polar-research-a-united-call-for-stronger-support/) - Europe’s polar research: a united call for stronger support More than 40 coordinators of EU Polar Cluster projects have co-signed a joint letter to EU leaders and decision-makers. Representing the scientific, technical, and operational backbone of Europe’s polar research community, the Cluster highlights that changes in the Arctic and Antarctic have direct consequences for Indigenous peoples, Arctic
- [News: The nighttime cloud effect](https://certainty-aci.eu/news-the-nighttime-cloud-effect/) - The nighttime cloud effect About 67% of Earth’s surface is covered by clouds at any moment*. These extensive cloud layers play a major role in regulating Earth’s temperature.Each cloud droplet forms on an aerosol particle (mostly from natural sources, such as desert dust or sea salt). Human-emitted aerosols (especially fossil-fuel combustion) create more, smaller droplets in
- [News: How will CERTAINTY contribute to CMIP7](https://certainty-aci.eu/news-how-will-certainty-contribute-to-cmip7/) - How will CERTAINTY contribute to CMIP7? The Coupled Model Intercomparison Project (CMIP) of the World Climate Research Programme is an international climate modelling project designed to better understand past, present and future changes in the climate. CMIP has been coordinating model experiments across the climate science community since 1995. Over the years, it has become
- [Clouds & Climate: A Fireside Chat with Gavin Pretor-Pinney & Ed Gryspeerdt](https://certainty-aci.eu/clouds-climate-a-fireside-chat-with-gavin-pretor-pinney-ed-gryspeerdt/) - Clouds & climate: a fireside chat with Gavin Pretor-Pinney & Ed Gryspeerdt CERTAINTY researcher Ed Gryspeerdt joined Gavin Pretor-Pinney* for a special online fireside chat organized by Asterisk Labs and the Cloud Appreciation Society. Together, they explored the wonder of clouds and their vital role in Earth’s climate system, bridging science, beauty, and public engagement. They discussed
- [News: Cumulus clouds amplify boreal forest photosynthesis](https://certainty-aci.eu/news-cumulus-clouds-amplify-boreal-forest-photosynthesis/) - Cumulus clouds amplify boreal forest photosynthesis Boreal forests, covering 14% of Earth’s land, are key players in the climate system. They store carbon, regulate energy and water cycles, and release aerosols that interact with the atmosphere.A new study by Ezhova et al., based on long-term observations at the SMEAR II station in Finland, shows that organic aerosols enhance photosynthesis under
- [News: Climate effects of the 2023 Canadian wildfires](https://certainty-aci.eu/news-climate-effects-of-the-2023-canadian-wildfires/) - Climate effects of the 2023 Canadian wildfires The 2023 Canadian wildfires marked an unprecedented environmental event, with around 5% of Canada’s forested land burned, seven times higher than the long-term average burnt area. These fires produced record-breaking emissions, releasing vast amounts of carbon dioxide, aerosols, and reactive gases that severely affected both air quality and the climate. Such
- [News: Urban pollution in the Amazon wet season: minimal impact on aerosol, cloud and rain](https://certainty-aci.eu/news-urban-pollution-in-the-amazon-wet-season-minimal-impact-on-aerosol-cloud-and-rain/) - Urban pollution in the Amazon wet season: minimal impact on aerosol, cloud and rain Anthropogenic emissions* influence aerosol formation, cloud properties, and rainfall, but their effects are highly variable and uncertain. During the wet season of the Amazon rainforest, pollution from the Brazilian city Manaus can substantially increase cloud condensation nuclei compared to the natural
- [News: Aerosols’ direct radiative effect strengthens despite falling emissions](https://certainty-aci.eu/news-aerosols-direct-radiative-effect-strengthens-despite-falling-emissions/) - Aerosols’ direct radiative effect strengthens despite falling emissions Hermant, A., Huusko, L., and Mauritsen, T.: Increasing aerosol direct effect despite declining global emissions in MPI-ESM1.2, Atmos. Chem. Phys., 24, 10707–10715, https://doi.org/10.5194/acp-24-10707-2024, 2024. Aerosols (small particles emitted by natural and human sources) influence Earth’s climate both by scattering sunlight directly and by altering cloud properties, which
- [News: Impacts of shipping fuel regulations on global warming](https://certainty-aci.eu/news-impacts-of-shipping-fuel-regulations-on-global-warming/) - Impacts of shipping fuel regulations on global warming The 2020 International Maritime Organization regulation (IMO2020) limits sulfur in shipping fuel to improve health and air quality. This change reduced sulfate aerosol emissions, which in turn weakened the cooling effect normally provided by marine clouds.A recent study by Zhang et al. used machine learning to distinguish natural
- [Partner projects and programs](https://certainty-aci.eu/partner-projects-and-programs/) - Partner projects and programs The International Advisory Committee The project aims to engage the specific stakeholders that are members of the CERTAINTY IAC to ensure:-- needs are integrated into the project during operation; impacts are maximized through two-way engagement with the IPCC, CMIP, ACTRIS, ESA, EUMETSAT, and Copernicus Services (CAMS/C3S). This is initiated through stakeholder
- [Open data](https://certainty-aci.eu/open-data/) - Open data Visit our Zenodo community to access our publications, datasets and codes
- [News: Tracing the origins of particles in polar regions](https://certainty-aci.eu/news-tracing-the-origins-of-particles-in-polar-regions/) - Tracing the origins of particles in polar regions Understanding the origins of particles and trace gases in rapidly changing polar climates is crucial for accurate climate models, especially regarding how these particles interact with clouds. Since direct measurements in these remote regions are difficult and expensive, scientists often use 'backward modeling' to trace atmospheric compounds back
- [News: Kickoff](https://certainty-aci.eu/kickoff/) - CERTAINTY kickoff in Brussels The CERTAINTY Project Kickoff Meeting took place from February 27th to February 29th, 2024, at Maison Irène et Frédéric Joliot-Curie in Brussels, Belgium. The meeting aimed to initiate discussions and collaborations among project partners funded by the Horizon Europe programme.Throughout the meeting, participants engaged in insightful discussions, exchanged ideas, and outlined
- [News: EGU 2025](https://certainty-aci.eu/egu-2025/) - CERTAINTY researchers at EGU 2025 Don’t miss the chance to discover the latest insights from our researchers! Join us at EGU 2025 in Vienna to learn more about our work. EGU25-19417 | ECS | Orals | AS3.11Short time-scale evolution of aerosol-cloud interactionsVishnu Nair and Edward GryspeerdtTue, 29 Apr, 11:05–11:15 (CEST) Room F2EGU25-18477 | ECS |
- [2025 Annual meeting](https://certainty-aci.eu/2025-annual-meeting/) - 2025 CERTAINTY Annual Meeting: strengthening collaborations & shaping future directions The CERTAINTY annual meeting was held in Grenoble (France) from 11 to 14 February 2025, marking an important milestone as we enter Year 2 of the project. The meeting provided a valuable opportunity to assess our progress, align on strategic goals, and strengthen collaborations with
- [Quiz](https://certainty-aci.eu/quiz/) - QUIZ
- [Leaflet](https://certainty-aci.eu/leaflet/) - Leaflet Click here to download the trifold brochure for printing:
- [Contact](https://certainty-aci.eu/contact/) - Contact & Newsletter Email us Full Name*Email*Message*Send Message Subscribe to our newsletter Full Name*Email*Send Message Follow us Bluesky LinkedIn Twitter Mastodon
- [News: Observation of aerosols and clouds](https://certainty-aci.eu/news-observation-of-aerosols-and-clouds/) - Observation of aerosols and clouds To reduce uncertainty in our understanding of aerosols and clouds and to improve our predictions of their current and future impact on climate, we need observational systems that can provide constraint on our model tools. Climate models seek to replicate the state of the global system and predict its future change
- [News: Modeling sea spray emission from leads in the Arctic](https://certainty-aci.eu/news-modeling-sea-spray-emission-from-leads-in-the-arctic/) - Modeling sea spray emission from leads in the Arctic Sea spray aerosols constitute the majority of the aerosol mass in polar regions annually and are a key factor influencing the polar climate through the aerosol direct radiative effect and through aerosol-cloud interactions. These aerosols can be emitted also in sea ice regions, although such sources
- [News: The role of dust in weather and climate](https://certainty-aci.eu/the-role-of-dust-in-weather-and-climate/) - The role of dust in weather and climate Desert dust, created by wind erosion in arid regions, is the main source of ice-nucleating particles (INPs) in the atmosphere, which are crucial for determining the balance between ice crystals and liquid droplets in mixed-phase clouds (MPCs). Without INPs, cloud droplets in MPCs would remain liquid until
- [News: Setting a standard for transparency and research accessibility](https://certainty-aci.eu/setting-a-standard-for-transparency-and-research-accessibility/) - Setting a standard for transparency and research accessibility The CERTAINTY project is dedicated to advancing scientific discovery through open and FAIR (Findable, Accessible, Interoperable, and Reusable) principles, ensuring that data and publications are both accessible and structured for broad utilization within and beyond the scientific community. A well-planned Data Management Plan underpins all our actions, facilitating
- [News: New Horizon Europe Project focus on improved understanding of Clouds and Aerosols in Weather and Climate](https://certainty-aci.eu/new-horizon-project/) - New Horizon Europe Project focus on improved understanding of Clouds and Aerosols in Weather and Climate CERTAINTY: Cloud-aERosol inTeractions & their impActs IN The earth sYstem project, funded by the Horizon Europe program, aims to advance our comprehension of clouds and aerosols in the climate. This project strives to refine and use observations and models
- [News: Impact of tailored climate information on attitudes towards climate policies and perceived distance to climate change](https://certainty-aci.eu/impact-of-tailored-climate-information-on-attitudes-towards-climate-policies-and-perceived-distance-to-climate-change/) - Impact of tailored climate information on attitudes towards climate policies and perceived distance to climate change A new study by Mira Hulkkonen, Tero Mielonen, Saara Leppänen, Anton Laakso and Harri Kokkola, involving over 1,000 Finns used an innovative interactive tool to assess the impact of tailored climate information on knowledge, attitudes, and psychological detachment from climate change. The tool
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