Varghese et al. (2026) Global compound drought–hot events: insights from a 3D-event based framework, intercontinental synchronization, and the evolving influence of climatic drivers

Identification

• Journal: Journal of Hydrology
• Year: 2026
• Authors: Femin C. Varghese, Sakila Saminathan, Subhasis Mitra
• DOI: 10.1016/j.jhydrol.2026.135050

Research Groups

• Department of Civil Engineering, Indian Institute of Technology (IIT) Palakkad, Kerala, India.

Short Summary

This study implements a three-dimensional (3D) event-based framework to characterize the spatiotemporal evolution of global compound drought–hot events (CDHEs) from 1951 to 2022. The research identifies a shift in the primary drivers of these events, showing a weakening influence of ENSO and a growing dominance of anthropogenic warming.

Objective

• To detect and characterize the persistence, migration, and large-scale synchronization of global CDHEs using a continuous space-time (3D) framework.
• To evaluate the sensitivity of CDHE detection to index selection and identify the evolving influence of climatic drivers.

Study Configuration

• Spatial Scale: Global land areas, with specific regional hotspots identified in the Amazon, Central Africa, Northern North America, Russia, and China.
• Temporal Scale: 1951–2022 (72-year period).

Methodology and Data

• Models and Indices used:
  • Blended Dry and Hot Index (BDHI): Used as the primary indicator for compound extremes.
  • 3D Event-Based Framework: A method that treats extremes as continuous volumes in space and time to track initiation, growth, migration, and dissipation.
  • Complex Network (CN) Analysis: Employed to uncover intercontinental synchronization patterns and hubs.
  • Uncertainty Analysis: Comparison of various drought and compound indices (e.g., SDHI, SCEI) across different aridity zones.
• Data sources: Global climate datasets covering temperature and precipitation for the period 1951–2022.

Main Results

• Event Characterization: Identified 809 distinct 3D-CDHEs globally. Most events last 3–6 months and cover an area of 1–10 million $km^2$.
• Temporal Trends: Large-scale, persistent events lasting longer than 12 months have become significantly more frequent in recent decades.
• Synchronization Hubs: Complex network analysis identified major synchronization hubs in the Amazon, West Africa, the Mediterranean, Southeast Asia, and North Asia.
• Driver Evolution: While many synchronization patterns were historically linked to El Niño–Southern Oscillation (ENSO) episodes, the ENSO–CDHE relationship is weakening. Anthropogenic global warming has emerged as the primary driver of these compound extremes.
• Sensitivity: CDHE detection is highly sensitive to the choice of index, with uncertainties increasing under recent accelerated warming conditions.

Contributions

• Methodological Innovation: Advances beyond traditional grid-by-grid analysis by utilizing a 3D framework that preserves the spatial and temporal continuity of climate extremes.
• Synchronization Insights: Provides a novel mapping of how compound extremes are synchronized across continents using complex network theory.
• Climate Attribution: Offers empirical evidence of the shifting balance between natural climate variability (ENSO) and anthropogenic forcing in driving global compound hazards.

Funding

• Not specified in the provided text.

Citation

@article{Varghese2026Global,
  author = {Varghese, Femin C. and Saminathan, Sakila and Mitra, Subhasis},
  title = {Global compound drought–hot events: insights from a 3D-event based framework, intercontinental synchronization, and the evolving influence of climatic drivers},
  journal = {Journal of Hydrology},
  year = {2026},
  doi = {10.1016/j.jhydrol.2026.135050},
  url = {https://doi.org/10.1016/j.jhydrol.2026.135050}
}

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