ESiWACE3 has delivered results that surpass the state of the art in European weather and climate modelling. The HPCW benchmark is a central achievement, encapsulating model complexity in a vendor-usable way that enables co-design and robust evaluation of novel architectures, from GPU-based systems to RISC-V. A governance plan ensures its sustained use on EuroHPC machines and synergies with initiatives like HANAMI. Work on DSLs has advanced portability and performance strategies, accelerating adaptation of complex codes to heterogeneous systems and ensuring sustainability of major models on future exascale platforms. On the data front, ESiWACE3 has pioneered new approaches to storage, cataloguing, and compression. FAIR Digital Objects and compression benchmarks offer transformative solutions to the massive volumes expected from exascale simulations, ensuring datasets remain accessible, interoperable, and reproducible. The project has also shown that complex models can be efficiently ported to CPUs and GPUs, supported by workflows for reduced-precision computing, automated profiling, and portability. Collectively, these innovations prepare the community for exascale computing. Beyond technical advances, ESiWACE3 has strengthened capacity through training, open-source releases, and inclusive strategies. Results are widely adopted, particularly by early-career scientists benefiting from mentoring. Looking ahead, sustained investment in software sustainability, FAIR standards, and international collaboration will be key. By delivering these results, ESiWACE3 accelerates discovery, fosters innovation, and consolidates Europe’s global leadership in high-resolution climate and weather modelling.
