Su et al. (2026) Assessing drought changes in China under a CO2 removal scenario

Identification

• Journal: Geoscience Letters
• Year: 2026
• Date: 2026-03-05
• Authors: Xiaoyun Su, Lin Wang, Gang Huang, Ting Wang
• DOI: 10.1186/s40562-026-00466-1

Research Groups

• Department of Mathematics, North University of China, Taiyuan, China
• National Key Laboratory of Earth System Numerical Modeling and Application, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, China
• College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing, China
• Temperate East Asia Research Center on Global Change, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, China
• Laboratory of Middle Atmosphere and Global Environment Observation (LAGEO), Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, China

Short Summary

This study evaluates regional drought responses in China to CO2 removal (CDR) scenarios, revealing a 5–10 year lagged drought recovery and incomplete, regionally heterogeneous reversibility even after CO2 returns to pre-industrial levels. The findings highlight the critical role of climatic inertia and the necessity for region-specific adaptation strategies in carbon-neutral pathways.

Objective

• To systematically evaluate drought evolution, driving mechanisms, and event characteristics (frequency, duration, and severity) across China and its six subregions under an idealized CO2 removal scenario. The study specifically assesses the effectiveness of CDR in mitigating drought and the reversibility of drought changes after CO2 concentrations return to pre-industrial levels.

Study Configuration

• Spatial Scale: China, divided into six subregions (Northwest China, Southwest China, Northeast China, North China, Yangtze River Valley, and Southeast China). Final model outputs are at a spatial resolution of 0.5° × 0.5°.
• Temporal Scale:
  • Idealized CO2 removal (CDR) experiments from CMIP6 (1pctCO2-cdr).
  • CO2 ramp-up period: Years 1–140 (CO2 increases by 1% per year).
  • CO2 ramp-down period: Years 141–280 (CO2 decreases by 1% per year, returning to initial levels).
  • CO2 stabilization period (St): Years 281–340.
  • Pre-industrial (PI) period: Last 100 years of the piControl experiment.
  • Peak CO2 (Pk) period: 20-year mean around peak CO2 (Years 131–150).
  • Observational reference period (CRU): 1979–2014.

Methodology and Data

• Models used: Five Coupled Model Intercomparison Project Phase 6 (CMIP6) global climate models (GCMs): ACCESS-ESM1-5, CanESM5, CNRM-ESM2-1, GFDL-ESM4, and MIROC-ES2L. Experiments include historical, piControl, 1pctCO2, and 1pctCO2-cdr.
• Data sources:
  • Observational data: Climatic Research Unit (CRU) TS4.07 for monthly precipitation and potential evapotranspiration (PET) at 0.5° × 0.5° resolution.
  • Drought Index: Standardized Precipitation Evapotranspiration Index (SPEI), calculated using the Penman-Monteith equation for PET.
  • Bias Correction and Spatial Downscaling (BCSD): Equiratio Cumulative Distribution Function Matching (EQCDF) method and statistical downscaling applied to GCM outputs, using CRU data as reference to achieve 0.5° × 0.5° resolution.
  • Attribution method: Control-variable attribution approach to quantify contributions of precipitation, PET, and their joint effect to SPEI changes.
  • Drought identification: Run theory, defining a drought event as ≥ 3 consecutive months with negative SPEI and lowest SPEI < -1. Extreme drought events are defined as ≥ 3 consecutive months with SPEI < -2. Metrics include Mean Drought Frequency (MDF), Mean Drought Duration (MDD), and Mean Drought Severity (MDS).

Main Results

• Lagged Response: Drought conditions continue to decline for 5–10 years after rapid CO2 removal begins before gradually recovering.
• Drought Mitigation: CO2 removal generally leads to less frequent, shorter-duration, and less severe drought events across China. Extreme droughts are primarily alleviated through reduced persistence and intensity, rather than a significant decrease in occurrence.
• Incomplete and Heterogeneous Recovery: Even after atmospheric CO2 returns to pre-industrial levels, drought recovery is incomplete and regionally heterogeneous. Residual drying persists in Northwest, North, and Southeast China, while the Yangtze River Valley shows an over-recovery in drought duration.
• Regional Attribution of Drivers:
  • Arid regions (Northwest China): SPEI changes are predominantly controlled by potential evapotranspiration (PET) (62%).
  • Semi-arid to semi-humid regions (Southwest, Northeast, and North China): Precipitation is the primary driver (43–51%).
  • Humid regions (Yangtze River Valley and Southeast China): Drought variability is jointly governed by precipitation (46–48%) and its nonlinear interaction with PET (37–43%).
• Spatial Heterogeneity in Mitigation: The strongest drought mitigation benefits from CDR are observed in Northwest and Northeast China, with moderate effects in Southwest and Southeast China, and limited influence in North China and the Yangtze River Valley.

Contributions

• This study provides the first comprehensive regional assessment of drought evolution, driving mechanisms, and event characteristics in China under an idealized CO2 removal scenario, utilizing a bias-corrected and spatially downscaled multi-model SPEI dataset.
• It quantifies the significant temporal lags and pronounced regional disparities in drought responses to CO2 removal, highlighting the critical role of hydroclimatic inertia and the potential for incomplete reversibility.
• The research establishes a robust, stable, and region-specific attribution framework for drought changes, demonstrating how the dominant drivers (precipitation, PET, and their interaction) vary systematically along China's dry-wet gradient and remain consistent throughout CO2 concentration changes.
• The findings underscore the necessity for tailored, region-specific adaptation strategies in the design of future carbon-neutral pathways, acknowledging the persistent residual drought risks and spatial heterogeneity even after substantial CO2 removal.

Funding

• National Key R&D Program of China (Project No. 2025YFF 0812000)
• National Natural Science Foundation of China (Grants Nos. 42575036, 42530606, and 42261144687)
• International Partnership Program of Chinese Academy of Sciences for Future Network (Grant No. 060GJHZ2022104FN)
• Technical support from the National Large Scientific and Technological Infrastructure “Earth System Numerical Simulation Facility”

Citation

@article{Su2026Assessing,
  author = {Su, Xiaoyun and Wang, Lin and Huang, Gang and Wang, Ting},
  title = {Assessing drought changes in China under a CO2 removal scenario},
  journal = {Geoscience Letters},
  year = {2026},
  doi = {10.1186/s40562-026-00466-1},
  url = {https://doi.org/10.1186/s40562-026-00466-1}
}