Drought: Observed trends, future projections

Drought quantification is difficult since a drought is usually identified by its effects or by its impacts on different types of systems, but no single physical variable can be measured to quantify drought. Droughts are also difficult to pinpoint in time and space since their onset, ending, duration, magnitude, and spatial extent are not easy to define. Thus, drought is often quantified indirectly using indices, which are often based on meteorological, hydrological and/or remote sensing data, and physical models help us understand the relevant processes and make predictions. In this sub-chapter, we describe and discuss drought in the Mediterranean together with some relevant processes, and comment on possible future scenarios.