Storylines for Global Hydrologic Drought Within CMIP6

Abstract

Abstract Future global increases in the duration and severity of hydrologic drought present an emerging challenge for water resource management. However, projected changes to drought within global climate models are often complex, including potentially co‐occurring changes to the timing, duration, and severity of drought. Here, we apply a storyline approach for interpreting projections of future hydrologic drought to identify coherent narratives that include runoff trends, shifts in the seasonal drought timing, increases in multi‐year drought frequency, and increased drought severity within the Coupled Model Intercomparison Project Phase 6. We develop a framework to classify future drought storylines (2015–2100) and quantify model consensus to determine the most‐likely “dominant” storyline under four emission scenarios Shared Socioeconomic Pathways (SSPs) 1–2.6, 2–4.5, 3–7.0, and 5–8.5. Under a low‐emission scenario (SSPs 1–2.6) approximately one third of the land‐area is projected to be impacted by a dominant storyline of minimally detectable runoff trend paired with increased frequency of multi‐year drought. However, under the highest‐emission scenarios (SSPs 5–8.5), the most likely storyline shifts to an increase in multi‐year drought frequency, increased severity of drought, and negative long‐term runoff trends for 62% of the area in those same regions. Shifts in the seasonal timing of drought are a component of dominant storylines for the northern latitudes across all emission scenarios. These results provide an alternative mode of interpretation of co‐occurring changes to the features of future drought, framed in a way to support regional adaptation strategies to mitigate future drought impacts.

Keywords

• hydrologic drought
• storylines
• CMIP6
• climate change
• multi‐year drought