Evidence of increasing drought severity caused by temperature rise in southern Europe

TLDR

The study uses high‑quality Iberian climate data and drought indices, and analyzes streamflow records from 287 rivers, to show that rising temperatures have increased atmospheric evaporative demand and consequently drought severity and hydrological drought frequency over the past five decades. Drought severity and hydrological drought frequency have risen independently of evapotranspiration models, with higher evaporative demand driving streamflow reductions in the warm season, a pattern that likely extends to other semiarid regions and threatens future water security.

Abstract

We use high quality climate data from ground meteorological stations in the Iberian Peninsula (IP) and robust drought indices to confirm that drought severity has increased in the past five decades, as a consequence of greater atmospheric evaporative demand resulting from temperature rise. Increased drought severity is independent of the model used to quantify the reference evapotranspiration. We have also focused on drought impacts to drought-sensitive systems, such as river discharge, by analyzing streamflow data for 287 rivers in the IP, and found that hydrological drought frequency and severity have also increased in the past five decades in natural, regulated and highly regulated basins. Recent positive trend in the atmospheric water demand has had a direct influence on the temporal evolution of streamflows, clearly identified during the warm season, in which higher evapotranspiration rates are recorded. This pattern of increase in evaporative demand and greater drought severity is probably applicable to other semiarid regions of the world, including other Mediterranean areas, the Sahel, southern Australia and South Africa, and can be expected to increasingly compromise water supplies and cause political, social and economic tensions among regions in the near future.