High-resolution Climate Projections for Ireland A Multi-model Ensemble Approach. EPA Report no. 339

The method of regional climate modelling was employed to assess the impacts of a warming climate on the 21st-century climate of Ireland. The regional climate model (RCM) simulations were run at high spatial resolution (3.8 and 4 km), the first systematic study of its kind at this scale, thus allowing a better evaluation of the local effects of climate change. To address the issue of uncertainty, a multi-model ensemble approach was employed. Through the ensemble approach, the uncertainty in the projections can be partly quantified, thus providing a measure of confidence in the projections. Simulations were run for the reference period 19812000 and the future period 20412060. Differences between the two periods provide a measure of climate change. The Consortium for Small-scale ModelingClimate Limited-area Modelling (COSMO-CLM) and Weather Research and Forecasting (WRF) RCMs were used to downscale the following Coupled Model Intercomparison Project Phase 5 (CMIP5) global climate model (GCM) datasets: CNRM-CM5, EC-EARTH (four ensemble members), HadGEM2-ES, MIROC5 and MPI-ESM-LR. To account for the uncertainty in future greenhouse gas emissions, the future climate was simulated under both the Representative Concentration Pathway 4.5 (RCP4.5) and RCP8.5 scenarios.