Mediterranean Climate Regions in CMIP6 experiments: assessment of future changes and associated uncertainties

Abstract

The mean climate characteristics of the Mediterranean region with temperate, wet winter and warm (or hot) dry summer is common to other regions of the world, like the west coast of North America, central Chile, the far southwest tip of Southern Africa and southwest Australia, which are all identified as Mediterranean climate regions (MCRs). Following from the Koppen-Geiger classification of climates, they share similar location and lie on the western edge of continents in the subtropics to mid-latitude thus being overall transition areas between wet and dry climates. In a previous work, with a probabilistic approach, we have quantified the risk of a poleward shift of MCRs, mostly over the Mediterranean region and western North America, with the equatorward margins replaced by arid climate type using CMIP5 21st century projections. Following on from the above and using newly available CMIP6 simulations we have designed an update of the assessment of future climate changes in MCRs. The objective is to identify how MCRs are projected to change in CMIP6 simulations either in terms of hydroclimate conditions and of expansion or retreat of the areas considering the high impact these changes may have on water resources, ecosystem and human livelihood over these vulnerable climate regions. On top of the overall picture of hydroclimate changes over the regions with commonalities and differences, as expected from current dynamical understanding, we will provide an evaluation of the uncertainties in the projections and estimates of the models’ reliability in representing observed past changes.