Introducing the New Urban Climate Layer in the Copernicus Interactive Climate Atlas

The Copernicus Interactive Climate Atlas (https://atlas.climate.copernicus.eu, C3S Atlas in short) evolves from the frozen IPCC Atlas (Gutiérrez et al., 2021; https://interactive-atlas.ipcc.ch/) to potentially address the needs of the IPCC’s seventh assessment cycle. A key novelty in the upcoming IPCC cycle is the inclusion of a Special Report on Climate Change and Cities (Decision IPCC-LXI-5), which motivated the WCRP CORDEX FPS URB-RCC to evaluate the capacity of current CORDEX simulations to represent urban effects on climate and provide insights for CMIP6-driven CORDEX simulations (Langendijk et al., 2024, https://doi.org/10.1016/j.uclim.2024.102165). The evaluation of CORDEX-CORE (25 km) (Langendijk et al., 2025, internal review) reveals that, although limited, these simulations can capture the nocturnal and diurnal Urban Heat Island (UHI) effect in various megacities. Despite significant gaps in spatial resolution, urban schemes, and the diversity of RCMs, these analyses highlight the need to address these limitations in future studies. Results show that the models’ ability to reproduce the UHI effect improved significantly with more advanced urban schemes and an increase in spatial resolution from 25 km to 12.5 km (over Europe). These findings advocate for the use of higher resolutions and to appropriately account for urban areas using up-to-date urban parameterizations in the new CORDEX-CORE CMIP6 simulations.

This work introduces the urban climate analysis layer in the C3S Atlas, aligned with the FPS-URB-RCC initiative. The urban layer analyzes the urban effects through spatial maps and seasonal anomalies between urban areas and their surroundings for several climatic impact-drivers (CIDs). REMO and RegCM models are used for CORDEX-CORE and EURO-CORDEX, covering different scenarios (RCP4.5, RCP8.5) and Global Warming Levels (e.g., 1.5, 2, 3, and 4 ºC). This analysis will be included in the next release of the C3S Atlas (spring 2025) and will provide global perspective based on existing worldwide regional projections focused on urban aspects.