High-Resolution Climate Projections for Ireland - An RCM-CMIP6 Multi-Model Ensemble

Regional Climate Models (RCMs) were used to simulate the climate of Ireland (1980-2100). The simulations were run at high spatial resolution (4km), allowing a more realistic representation of important physical processes and enabling a more accurate evaluation of the local impacts. To address the uncertainty inherent in climate model projections, three RCMs (COSMO-CLM, WRF and HCLIM) were used to dynamically downscale outputs from an ensemble of CMIP6 GCMs (CMCC-CM2-SR5, CNRM-ESM2-1, MIROC6, MPI-ESM1-2-HR, NorESM2-MM, ECEarth3-Veg and ECEarth3). The outer domain (used to drive the inner 4km domain) was run at 12km (COSMO-CLM) and 20km (WRF) grid spacings, and roughly corresponds to the Euro-CORDEX 12km domain. To account for the uncertainty in future global emissions, the future climate was simulated under all four tier-1 SSP–RCP (SSP1-2.6, SSP2-4.5, SSP3-7.0 and SSP5-8.5) emission scenarios. The resulting large ensemble size is essential for a more accurate quantification of climate change uncertainty.

The RCM configurations were validated by running simulations of the past Irish climate for the period 1980–2010, driven by both fifth-generation ECMWF atmospheric reanalysis of the global climate (ERA5) and the CMIP6 ESM datasets, and comparing the output against observational data.

In addition to the standard climate fields (e.g., temperature, precipitation, wind, snowfall, humidity and radiation), the research provides projections of additional derived variables such as wind power at turbine height, photovoltaic power, evapotranspiration and Universal Thermal Climate Index (UTCI).

The scenario-based projections are supplemented with global warming threshold scenario projections for temperature and precipitation.