The CIRCE simulations: Regional Climate Change Projections with Realistic Representation of the Mediterranean Sea

In this article we describe an innovative multi-model system developed within the CIRCE EU-FP6 Project and used to produce simulations of the Mediterranean Sea regional climate. The models include high-resolution Mediterranean Sea components, which allow to assess the role of the basin, and in particular of the air-sea feedbacks in the climate of the region. The models have been integrated from 1951 to 2050, using observed radiative forcings during the first half of the simulation period and the IPCC SRES A1B scenario during the second half. The projections show a substantial warming (about 1.5°-2°C) and a significant decrease of precipitation (about 5%) in the region for the scenario period. However, locally the changes might be even larger. In the same period, the projected surface net heat loss decreases, leading to a weaker cooling of the Mediterranean Sea by the atmosphere, whereas the water budget appears to increase, leading the basin to loose more water through its surface than in the past. These results are overall consistent with the findings of previous scenario simulations, such as PRUDENCE, ENSEMBLES and CMIP3. The agreement suggests that these findings are robust to substantial changes in the configuration of the models used to make the simulations. Finally, the models produce a 2021-2050 mean steric sea-level rise that ranges between +7 cm and +12 cm, with respect to the period of reference.