Climate change projections over mid-high latitudes Northern Asia using an ensemble of RegCM5 simulations

Mid-high latitudes Northern Asia (NAS) is highly sensitive to global warming, yet remains understudied—particularly for high-resolution regional climate model (RCM) based future climate change projections. This study conducts three sets of future climate experiments over the region using an RCM, the ICTP RegCM5 at a grid spacing of 25 km, driven by three CMIP6 models of EC-Earth3-Veg, MPI-ESM1-2-HR, and NorESM2-MM. Two time slices, 1995 to 2014 for the present day climate, and 2080 to 2099 for the future under the emission pathway of SSP2-4.5, are conducted. The analysis is focused on mean temperature and precipitation in the cold season December‒January‒February (DJF) and warm season of June‒July‒August (JJA). Results show the driving GCMs and nested RegCM5 reproduce the present day climate well while RegCM5 provides with more spatial details. The models show a consistent warm bias over northeastern part of the domain in DJF. Cold bias in JJA in the northeastern and warm bias in the southwestern part of the region, more pronounced in RegCM5, are found. The models exhibit a general wet bias during both DJF and JJA, also greater in RegCM5. Regionally averaged, the biases of GCM/RegCM5 in DJF and JJA are 1.8/0.1 °C and −0.3/−2.7 °C, and for precipitation are 0.24/1.17 mm/d and 0.46/0.31 mm/d, respectively. Pronounced warming is projected in the future. The warming is more pronounced in DJF compared to JJA. RegCM5 shows broad consistencies in the general pattern of the warming with the GCMs but with more spatial details and greater magnitudes. The projected regional mean values of warming by GCM/RegCM5 are 3.7/4.3 °C in DJF and 3.0/3.5 °C in JJA, respectively. Precipitation changes show large differences between RegCM5 and GCMs, mostly due to the amplified circulation changes. In DJF, while the GCMs show a dominant and consistent increase, RegCM5 projects extended areas of decrease (regional means as 23% and 4%, respectively). A regional mean decrease of precipitation in JJA is found in RegCM5 (−6%), while the GCMs show a slight increase (3%). This study provides the first high-resolution multi-model RCM simulations over Northern Asia, offering key insights into present-day climate and future projections for improved regional assessment.