Projected evolution of droughts and human exposure in the contiguous United States under SSP5-8.5: a regional downscaling perspective

Journal Article · Tue Aug 05 00:00:00 EDT 2025 · Environmental Research Letters

DOI:https://doi.org/10.1088/1748-9326/adf4f9· OSTI ID:2583777

Zhang, Leyuan ^[1]; Rubin, Hannah J. ^[1]; Chien, Rong-You ^[1]; Fu, Joshua S. ^[2]; Rastogi, Deeksha ^[3]; Kao, Shih-Chieh ^[3]; Ashfaq, Moetasim ^[3]

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1. Univ. of Tennessee, Knoxville, TN (United States)
2. Univ. of Tennessee, Knoxville, TN (United States); Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
3. Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)

The increasingly unpredictable and extreme weather patterns under a warming climate underscore the urgency of accurate regional assessments of future drought risk. This study evaluates the projected drought evolution in the contiguous United States under the high-emission shared socioeconomic pathway 5–8.5 climate scenario for the coming decades. Using a multi-model ensemble of six Coupled Model Intercomparison Project Phase 6 global climate models combined with dynamical downscaling techniques, we analyzed near-term (2020–2039) and mid-term (2040–2059) drought patterns using the self-calibrating palmer drought severity index (ScPDSI), the standardized precipitation index (SPI-12), and the Standardized Precipitation-Evapotranspiration Index (SPEI-12). Results reveal a widespread increase in abnormally dry (D0) and moderate drought (D1) conditions, particularly in urban areas, while severe (D2), extreme (D3), and exceptional (D4) droughts are expected to become less common in many regions. Meanwhile, persistent and intensifying droughts are projected in the western and southwestern U.S., driven by long-term soil moisture deficits. The ScPDSI projects that 1.1 million urban residents will be affected by D0 conditions in 2050, while SPI-12 suggests a decrease in the total affected populations after 2040. ScPDSI indicates prolonged droughts in the West, and SPI-12 captures transient variability. Although the total drought-exposed population is expected to decrease, urban areas will continue to bear a greater burden, particularly for mild droughts (D0, D1). These findings highlight a shift toward more frequent mild droughts, fewer severe droughts, and persistent drying in the Southwest, emphasizing the need for region-specific adaptation strategies.

• Research Organization: Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
• Sponsoring Organization: USDOE Office of Energy Efficiency and Renewable Energy (EERE); USDOE Office of Science (SC)
• Grant/Contract Number: AC02-05CH11231; AC05-00OR22725
• OSTI ID: 2583777
• Journal Information: Environmental Research Letters, Journal Name: Environmental Research Letters Journal Issue: 9 Vol. 20; ISSN 1748-9326
• Publisher: IOP Publishing
• Country of Publication: United States
• Language: English

Related Subjects

CMIP6
climate change
drought
population exposure
regional downscaling
soil moisture deficits