The path towards exascale computing holds enormous challenges for the community of weather and climate modelling regarding portability, scalability and data management that can hardly be faced by individual institutes. ESiWACE2 will therefore link, organise and enhance Europe's excellence in weather and climate modelling to (1) enable leading European weather and climate models to leverage the performance of pre-exascale systems with regard to both compute and data capacity as soon as possible and (2) prepare the weather and climate community to be able to make use of exascale systems when they become available. To achieve this goal, ESiWACE2 will (a) improve throughput and scalability of leading European weather and climate models and demonstrate the technical and scientific performance of the models in unprecedented resolution on pre-exascale EuroHPC systems, (b) evaluate and establish new technologies such as domain specific languages and machine learning for use in weather and climate modelling, (c) enhance HPC capacity via services to the weather and climate community to optimize code performance and allow model porting, (d) improve the data management tool chain from weather and climate simulations at scale, (e) foster co-design between model developers, HPC manufacturers and HPC centres, and (f) strengthen interactions of the community with the European HPC Eco-system. ESiWACE2 will deliver configurations of leading models that can make efficient use of the largest supercomputers in Europe and run at unprecedented resolution for high-quality weather and climate predictions. This will be a beacon for the community in Europe and around the world. ESiWACE2 will develop HPC benchmarks, increase flexibility to use heterogeneous hardware and co-design and provide targeted education and training for one of the most challenging applications to shape the future of HPC in Europe.

The European Climate Prediction system project (EUCP) has four objectives, all directly relevant to the work programme, and fully meet the challenge, scope and impact of the work programme. 1. Develop an innovative ensemble climate prediction system based on high-resolution climate models for Europe for the near-term (~1-40years), including improved methods used to characterise uncertainty in climate predictions, regional downscaling, and evaluation against observations. 2. Use the climate prediction system to produce consistent, authoritative and actionable climate information. This information will be co-designed with users to constitute a robust foundation for Europe-wide climate service activities to support climate-related risk assessments and climate change adaptation programmes. 3. Demonstrate the value of this climate prediction system through high impact extreme weather events in the near past and near future drawing on convection permitting regional climate models translated into risk information for, and with, targeted end users. 4. Develop, and publish, methodologies, good practice and guidance for producing and using authoritative climate predictions for 1-40year timescale. The system (objective1) will combine initialised climate predictions on the multi-annual timescale with longer-term climate projections and high resolution regional downscaling, using observations for evaluation. Methodologies will be developed to characterise uncertainty and to seamlessly blend the predictions and projections. Users will be engaged through active user groups. The system will be utilised (objective2) with users to co-produce information suitable for European climate service activities. A set of demonstrators will show the value of this information in real-world applications with user involvement (objective3). Key outputs will include disseminating and publishing the project’s methodologies, and user-relevant data and knowledge (objective4).

COMFORT will close knowledge gaps for key ocean tipping elements under anthropogenic physical and chemical climate forcing through an interdisciplinary research approach. It will provide added value to decision and policy makers in terms of science based safe marine operating spaces, refined climate mitigation targets, and feasible long-term mitigation pathways. We will determine the consequences of passing tipping points in physical tipping elements for the marine carbon, oxygen, and nutrient cycles, as well as tipping points in biogeochemical tipping elements. The respective impact on marine ecosystems will be determined. Projections of the Earth system and impact studies have so far been carried out sequentially in a chain from scenarios to projections to off-line impact studies. This sequential workflow has hampered a quick response of the impact community back to revised scenarios and projections for tackling climate mitigation. COMFORT breaks new ground by bringing together experts from Earth system science, oceanography, fisheries science and ecology in a single integrated project who will work in parallel with a consistent set of analysis tools, scenarios, and interoperable models. The strength of COMFORT lies in the system-focused interdisciplinary approach as opposed to existing studies at the level of individual subsystems. The approach will be pursued with a firm link to stakeholders. COMFORT results will contribute to all four expected impacts for this call.

The goal of UrbanAIR is to develop a new digital twin that supports decision-makers in urban areas to deal with urban design dilemmas in atmospheric heat and air quality to maximise the health and socio-economic well-being of its citizens affected by climate change. It will provide critical tools for climate adaptation and hazard control through urban design and planning, including very high-resolution model components of the urban atmosphere. UrbanAIR is designed by a consortium that covers the full value chain to revolutionize digital twin platforms by starting from the perspective of the end user. Through co-creation with the end users and a balanced evaluation of the decision criteria, the overall objective of UrbanAIR is to yield a dynamic, user-friendly infrastructure integrated into the Destination Earth infrastructure that empowers municipalities and industries to face urgent urban climate risks. The scales in the atmospheric models in UrbanAIR cover the full range from the regional to the neighbourhood level. This innovative multiscale approach is achieved through the development of software interfaces for the modular coupling of atmospheric models. AI-based emulators allow for the acceleration of these computationally expensive models, which, together with the application of advanced data assimilation techniques, allows the quantification of risks and uncertainties for the UrbanAIR scenarios. Corresponding behavioural models simulate the human response to changes in climate and associated hazards. The resulting scenarios form the input to the objective evaluation of the criteria for decision-making. With these science-based tools for scenario simulation of natural and human behaviour, reliable risk assessment, and balanced decision analysis, UrbanAIR will develop tools and the infrastructure to support decision-makers in cities. This will pave the way for effective climate adaptation by developing tools for a safer, healthier, and more resilient future.