Changes in the future summer Mediterranean climate: contribution of teleconnections and local factors

Abstract

Abstract. The realistic simulation of the summer Mediterranean climate requires not only refined spatial scales, but also an adequate representation of land-atmosphere interactions and teleconnections. Addressing all of these issues remains a challenge for most of the CMIP3/CMIP5 generation models. In this study we analyze high-resolution (~0.5° lat x lon) RCP8.5 future projections of the Geophysical Fluid Dynamics Laboratory CM2.5 model with a new incorporated land model (LM3). The simulated regional future changes suggest pronounced warming and drying over most parts of the Mediterranean. However the changes are distinctively less radical when compared with the CMIP5 multimodel ensemble. Moreover, changes over the Southeast (off the coast area of the Balkans) and Central Europe indicate not only a very modest warming, compared to the CMIP5 projections, but also wetting tendencies. The difference of CM2.5 projections of future changes over previous-generation models highlights the importance of a) a correctly projected magnitude of changes of the North Atlantic Oscillation and its regional impacts, which have the capacity to partly offset the anthropogenic warming and drying over the western and central Mediterranean; b) a refined representation of land surface-atmospheric interactions, which are a governing factor for thermal- and hydro-climate over Central and Southeastern Europe. The CM2.5 projections also indicate a maximum of warming (Levant) and drying (Asia Minor) over the eastern Mediterranean. The changes derived in this region indicate a decreasing influence of atmospheric dynamics in maintaining the regional temperature and precipitation balance and instead an increasing influence of local surface temperature on the local surface atmospheric circulation.