mediterranean projections

Repository for the code used to compute the diagnostics in:

The Mediterranean climate change hotspot in the CMIP5 and CMIP6 projections

Abstract:
The Mediterranean has been identified as a climate change hotspot due to an increased warming trend and precipitation decline. We compare projections of multiple CMIP5 and CMIP6 historical and scenario simulations to estimate the impacts of the ongoing climate change on the region. In particular, we investigate changes in temperature and precipitation for the 21st century under scenarios RCP2.6/SSP1-2.6, RCP4.5/SSP2-4.5 and RCP8.5/SSP5-8.5, as well as the high resolution HighResMIP experiments. A model weighting scheme is applied to obtain constrained estimates of projected changes, accounting for historical model performance and inter-independence of the multi-member multi-model ensembles, using an observational ensemble as reference. Results indicate a significant and robust warming over the Mediterranean during the 21st century over all ensembles and experiments. The amplified Mediterranean warming with respect to the global average is only found for summer. Projected changes vary between CMIP5 and CMIP6, with the latter projecting a stronger warming. In contrast to temperature, precipitation changes show a higher level of uncertainty and spatial heterogeneity. However, for the high emission scenario, a robust decline in precipitation is projected for large parts of the region during summer. While there is less disagreement in projected precipitation between CMIP5 and CMIP6, the latter shows larger precipitation declines in some regions. Results applying the model weighting scheme lead to reductions in CMIP6 and increases in CMIP5 warming trends, thereby reducing the differences between the two multi-model ensembles.