Future changes and associated uncertainties over the Mediterranean Climate Regions

The Mediterranean climate regions (MCRs) of the world, including the west coast of North America, central Chile, the far southwest tip of Southern Africa and southwest Australia, are characterized by temperate, wet winter and warm (or hot) dry summer, and they are typically located on the western edge of continents in the subtropics to mid-latitude sectors. In a previous work, adopting a probabilistic approach and using CMIP5 21^st century projections, we quantified the risk of a poleward shift of MCRs, mostly over the Mediterranean region and western North America, with their equatorward margins replaced by arid climate type.

Following on from the above and exploiting newly available CMIP6 simulations and sensitivity experiments, we have designed an updated assessment of future climate changes in MCRs. The objective is to identify how MCRs are projected to change in terms of hydroclimate conditions, as they all are transitions areas between wet and dry climates. Future projections indicate an increased probability of a MED climate-type poleward, while a reduced probability of this direction of change is projected equatorward (mostly evident in Northern Hemisphere MCRs and over South America). Over South Africa and Southern Australia a reduced probability to have MED climate-type is evident as well but the continents do not extend much poleward to clearly assess this change. In addition to the overall picture of hydroclimate changes in these regions with commonalities and differences as expected from current dynamical understanding, we have designed an evaluation of the uncertainties in the projections and estimates of the models’ reliability in representing observed past changes.