Aerosols and their interactions with clouds remain the largest source of uncertainty in predicting climate change at the regional scale. They influence how sunlight is reflected or absorbed, and how clouds form, evolve, and produce rain. Because aerosols respond rapidly to emission changes, reducing Aerosol-Cloud Interaction uncertainty is essential to guide effective climate action and ensure that clean-air policies also deliver climate benefits.

The EC–ESA Aerosol-Cloud Cluster brings together Europe’s leading experts in this field, linking Horizon Europe projects CleanCloud, CERTAINTY and AIRSENSE with other ESA initiatives. All three initiatives share the same overarching objective: enhancing our understanding of aerosol–cloud interactions to improve climate predictions and mitigation strategies. Together, they involve more than 220 researchers from nearly 40 institutions, fostering an unprecedented level of collaboration.

By combining state-of-the-art observations and modelling, the cluster strengthens Europe’s capability to assess climate risks, improve predictions, and guide effective climate policies and adaptation strategies for the benefit of communities across Europe and beyond.
These collaborations amplify research impact, consolidate the European and international ACI research community, and lay the groundwork for future programmes, models, and missions. Long-term legacy is embedded through a comprehensive exploitation strategy and strong alignment with major research infrastructures such as ACTRIS, as well as enhanced policy engagement, broader dissemination, continuous training, and strategic partnerships.

Joint publications

• Pfeifer, N., Mom, B., Moisseev, D. et al. Efficient ice multiplication from freezing raindrop fragmentation. Commun Earth Environ 6, 942 (2025). https://doi.org/10.1038/s43247-025-02953-3
• Chatziparaschos, M., Myriokefalitakis, S., Kalivitis, N., Daskalakis, N., Nenes, A., Gonçalves Ageitos, M., Costa-Surós, M., Pérez García-Pando, C., Vrekoussis, M., and Kanakidou, M.: Assessing the global contribution of marine aerosols, terrestrial bioaerosols, and desert dust to ice-nucleating particle concentrations, Atmos. Chem. Phys., 25, 9085–9111 (2025). https://doi.org/10.5194/acp-25-9085-2025