Extremes in temperature and precipitation around the Mediterranean basin in an ensemble of future climate scenario simulations

Abstract

A variable-grid atmospheric general circulation model, the LMDZ, with a local zoom over the Mediterranean is used to investigate potential future changes in climate extremes around the Mediterranean basin. Changes in extremes of annual minimum and maximum temperature, winter and summer 24-h maximum precipitation are discussed under the IPCC-A2 emission scenario. Three time slices of 30 years are chosen to represent respectively the end of the 20th century, the middle and the end of the 21st century. The boundary conditions were taken from the outputs of three global coupled climate models: from the Institut Pierre-Simon Laplace (IPSL), Centre National de Recherches Météorologiques (CNRM) and Geophysical Fluid Dynamics Laboratory (GFDL). These three global scenarios were used to estimate uncertainties associated with climate models. Extreme events are expressed in terms of return values, estimated from a Generalized Extreme Value distribution fitted to annual or seasonal extremes. The changes in distribution of extremes are analyzed to elucidate the nature of the changes in extremes. Magnitudes and main spatial patterns of the changes in extremes show a quite good consistency among three global scenarios. Comparison between changes in the middle and at the end of the 21st century does not reveal any remarkable discontinuity in future climate evolution. The maximum of warming occurs over Northeastern Europe for annual minimum temperature and over South Europe for annual maximum temperature. Averaged over the region, increase in cold extremes exceeds that in warm extremes. Changes in temperature extremes are mostly associated with shift of whole distribution (location parameter change) and in addition, for cold extremes, with changes in interannual variability, measured by the scale parameter. Mean precipitation changes are characterized by strong reduction belt over the Mediterranean and South Europe in winter, spring and summer. Precipitation extremes increase in all seasons except summer. These changes are predominantly associated with changes in the scale, but also with changes in the position and shape of the distribution. In general terms, it is suggested that the Mediterranean basin will experience a warmer climate with less total precipitation but more intense precipitation events.