Robustness and scalability of regional climate projections over Europe

Abstract

Climate change projections for Europe consistently indicate a future decrease in summer precipitation over southern Europe and an increase over northern Europe. However, individual models substantially modulate these overarching precipitation change signals. Despite considerable model improvements as well as increasingly higher model resolutions in regional downscaling efforts, these apparent inconsistencies so far seem unresolved. In the present study, we analyze European seasonal temperature and precipitation climate change projections using all readily available pan-European regional climate model projections for the twenty-first century with model resolution increasing from ≈50 to ≈12 km grid distances from the CORDEX modeling project. This allows for an in-depth analysis of what may be the most robust projection of the future climate. Employing a simple scaling with the global mean temperature change enables the identification of emerging robust signals of seasonal changes in temperature and precipitation. Likewise, the "what-if" approach, i.e., analyzing the climate change signal from transient experiments at the time of an emerging global temperature exceedance of e.g., 1, 2, or 3 degrees offers a policy relevant approach to providing more accurate projections. A comparison of the projections from these two approaches has never before been done in a comprehensive manner and is the subject of the present paper.