Bhatia et al. (2026) Regional responses to oceanic variability constrain global drought synchrony

Identification

• Journal: Communications Earth & Environment
• Year: 2026
• Date: 2026-01-06
• Authors: Udit Bhatia, Hemant Poonia, Danish Mansoor Tantary, Vimal Mishra, Rohini Kumar
• DOI: 10.1038/s43247-025-03111-5

Research Groups

• Department of Civil Engineering, Indian Institute of Technology Gandhinagar, India
• Department of Earth Sciences, Indian Institute of Technology Gandhinagar, India
• Department of Computational Hydrosystems (CHS), Helmholtz Centre for Environmental Research - UFZ, Leipzig, Germany
• Department of Computer Science and Engineering, Indian Institute of Technology Gandhinagar, India

Short Summary

This study analyzed global drought synchrony over 120 years (1901–2020), revealing that while rising temperatures exacerbate drought severity, regional precipitation variability, modulated by oceanic oscillations, limits the global extent of synchronized droughts to a maximum of 1.84% to 6.5% of the total land mass.

Objective

• To investigate how globally synchronous drought patterns have evolved over the past century in response to large-scale climatic variability.
• To understand how regional connectivity contributes to global drought synchronization.
• To determine how temperature and precipitation interactions shape synchronous global drought development.

Study Configuration

• Spatial Scale: Global, 0.5° × 0.5° grid resolution.
• Temporal Scale: 1901–2020/2021 (120 years), monthly and annual data, analyzed using 60-year sliding windows.

Methodology and Data

• Models used:
  • Self-Calibrating Palmer Drought Severity Index (sc-PDSI)
  • Complex Network Analysis (Event Synchronization, Degree Centrality, Clustering Coefficient, Average Link Length)
  • Maximum Covariance Analysis (MCA) / Singular Value Decomposition (SVD)
  • Mann-Kendall trend test
  • Jeffrey’s Divergence and Kolmogorov–Smirnov (KS) test for distribution comparison
  • Thornthwaite method for Potential Evapotranspiration (PET)
  • Sen’s slope estimator for trend calculation
• Data sources:
  • Gridded monthly sc-PDSI data (1901–2020, 0.5° × 0.5°) from the Climate Research Unit (CRU).
  • Temperature and precipitation fields (1901–2021, 0.5° × 0.5°) from CRU TS v4.07.
  • Sea surface temperature (SST) data from NOAA’s Extended Reconstructed SST V5 (ERSSTv5) (2.0° × 2.0°, monthly).
  • Global Dataset of Historical Yield (GDHY v1.2+v1.3) (1981–2016, 0.5° grid-cell) for maize, rice, wheat, and soybean.
  • Country-level annual crop-yield statistics (1961–2020) from the Food and Agriculture Organization of the United Nations (FAO).
  • Crop-area estimates from the MIRCA2000 high-resolution global cropping-area dataset.

Main Results

• The maximum synchronized drought area fluctuates between 1.84% and 6.5% of the total land mass, contrary to previous claims of up to one-sixth.
• A strong dependence exists between drought onset and local crop failures, with conditional probabilities of crop failure exceeding 50% in several key food-producing regions under moderate drought conditions (sc-PDSI ≤ -2).
• Global drought synchrony is driven by a dichotomy: temperature trends exacerbate it, while precipitation variability, modulated by sea surface temperature (SST) oscillations, limits its global extent.
• Prominent drought hubs were identified in South Africa, western North America, Australia, the Middle East, and South America.
• El Niño-Southern Oscillation (ENSO) phases reorganize drought coherence: El Niño years are characterized by higher node degree and low Average Link Length (indicating strong local clustering and spatially coherent droughts), while La Niña years show higher Average Link Length and reduced local clustering (more spatially heterogeneous and regionally dispersed droughts).
• The mean degree centrality of the drought network increased from 96 during 1901–1960 to 147 during 1961–2020, indicating increased connectivity among drought-affected regions.
• 54% of nodes exhibited increasing degree trends, with Australia showing the most significant increase in positive degree trends (88% of nodes).
• Maximum Covariance Analysis (MCA) revealed that the first mode of SST-scPDSI variability is strongly associated with ENSO, explaining approximately 37.6% of the squared covariance.
• Globally, precipitation variability accounts for approximately two-thirds (66% to 67%) of multi-decadal drought severity trends, with temperature-driven evaporative demand explaining the remaining one-third. The temperature contribution notably increased post-1990 in mid-latitude regions (e.g., Asia: 31% to 36%; Europe: 28% to 38%).

Contributions

• Provides a comprehensive analysis of the synchronized evolution of drought conditions globally using both linear and non-linear methods over a 120-year period.
• Quantifies the physical limits of global drought synchrony, challenging previous estimates of widespread synchronized drought impacts.
• Explicitly clarifies the distinct roles of temperature (exacerbating) and precipitation variability (modulating and limiting) in shaping global drought synchrony, mediated by oceanic variability.
• Offers insights into large-scale drought propagation and intensification mechanisms, supporting targeted resilience strategies for global food security and climate adaptation.
• Advances understanding of how large-scale climatic forcings interact with regional variability, providing a clearer foundation for predictive modeling and strategic resilience planning.

Funding

• Indian Institute of Technology Gandhinagar (primary funding support)
• ANRF (SERB) Network of Networks grant (Grant No. RES/SERB/CE/P0291/2324/0044)

Citation

@article{Bhatia2026Regional,
  author = {Bhatia, Udit and Poonia, Hemant and Tantary, Danish Mansoor and Mishra, Vimal and Kumar, Rohini},
  title = {Regional responses to oceanic variability constrain global drought synchrony},
  journal = {Communications Earth & Environment},
  year = {2026},
  doi = {10.1038/s43247-025-03111-5},
  url = {https://doi.org/10.1038/s43247-025-03111-5}
}