Model-based scenarios of Mediterranean droughts

This study examines the change in current 100-year hydrological drought frequencies in the Mediterranean in comparison to the 2070s as simulated by the global model WaterGAP. The analysis considers socio-economic and climate changes as indicated by the IPCC scenarios A2 and B2 and the global general circulation model ECHAM4. Under these conditions today's 100-year drought is estimated to occur 10 times more frequently in the future over a large part of the Northern Mediterranean while in North Africa, today's 100-year drought will occur less frequently. Water abstractions are shown to play a minor role in comparison to the impact of climate change, but can intensify the situation.

This study will, explicitly for the Mediterranean Region, examine whether the upward trend of droughts (IPCC, 2001), as described above, is likely to continue in the future, examining drought frequency as the main indicator. It will investigate the impacts of global change, including climate and socio-economic changes on future hydrological drought frequencies using two of the IPCC global emission scenarios, A2 and B2 (IPCC, 2000). These emission scenarios were constructed to explore future global developments of society and environment. Scenario A2 assumes a strong, but regionally oriented economic growth and fragmented technological change with an emphasis on human wealth, while B2 emphasizes the protection of the environment and social equity, but also relies on local solutions to economic, social, and environmental sustainability. Both scenarios represent a world in which the differences between developed and developing countries remain strong.

It is shown that climate change has a comparably stronger impact on the change in drought frequency than anthropogenic water uses. Water abstractions can, however, intensify drought conditions. On the other hand, this kind of drought analysis reaches its limits in a dry climate, as drought frequencies cannot increase in deserts and in these areas flows are too low to assume statistical significance of the changes.