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<p>Future drought projection studies typically use multi-model ensemble climate and hydrological simulations. In particular, precipitation, soil moisture, and streamflow simulations are used to quantify the changes in meteorological, agricultural, and hydrological droughts under future climate. Many different drought indices have thus been developed and employed in these projections with different indices often leading to varying states of future droughts. Recently, terrestrial water storage (TWS) has also been used to examine future droughts considering integrated climatic and hydrologic impacts on water stores. This presentation will shed light on drought projections using precipitation, soil moisture, runoff, and TWS drought indices and highlight uncertainties in these projections, including those arising from differences in drought definition or the diversity in drought indices. The presentation will then discuss how the consideration of vulnerability alters drought risk projections, specifically by incorporating human development projections as a proxy of broad vulnerability. Results presented will be based on several dozen ensemble hydrological simulations that include multiple climate models, hydrological models, Representation Concentration Pathways (RCPs), and Shared Socioeconomic Pathways (SSPs). Emphasis will be placed on global scale analyses and regional projections over drought hotspots. The results have appeared in three recent publications.</p>

The intensification of soil moisture drought events is an expected consequence of anthropogenic global warming. However, the implication of 1.5-3 °C global warming on these events remains unknown over North Africa and the Sahel region, where soil moisture plays a crucial role in food security that largely depends on rainfed agriculture. Here, using a multi-model ensemble from the Inter-Sectoral Impact Model Intercomparison Project phase 2b, we estimate the changes in the spatiotemporal characteristics of soil moisture drought events under increased global mean temperature. A 3 °C global warming results in multi-year (up to 19 years) mega-drought events over North Africa compared to a maximum drought duration of 12 years under the 1.5 °C Paris Agreement target. These events are projected to transform from historically severe droughts into exceptional droughts and extend over an area that is 32% larger under 3 °C compared to that under 1.5 °C. Global warming also leads to a high intensification of Sahelian drought extremes, in particular, their duration (from 24 to 82 months between 1.5 and 3 °C) over the western parts and their severity everywhere. Even though the results highlight substantial uncertainties arising from climate forcing and impact models, the projections indicate a tendency toward unprecedented exacerbation of soil moisture droughts that could pose serious threats to food security of North African and Sahelian societies in the absence of effective mitigation and adaptation.