The researchers asked whether the recent weakening of connections between Pacific and Indian Ocean climate patterns falls within natural variability, and whether large volcanic eruptions had disrupted the same relationships before industrial greenhouse warming.
The research question and why it matters
The researchers asked whether the recent weakening of connections between Pacific and Indian Ocean climate patterns falls within natural variability, and whether large volcanic eruptions had disrupted the same relationships before industrial greenhouse warming.
El Niño and Pacific Walker circulation changes are known to influence Indian Ocean temperatures and winds, and earlier work linked recent basin-wide Indian Ocean warming to greenhouse forcing. Paleoclimate studies also showed that volcanoes can alter tropical circulation. The new analysis joins these strands by reconstructing both basins with mostly marine proxies and testing the coupling itself over centuries and model ensembles.
What researchers found
The Indian and Pacific indices generally moved together over the preindustrial centuries, but both Indian Ocean relationships became unusual during roughly 1810–1850, when several tropical eruptions larger than Pinatubo occurred. Across 11 large eruptions and 13 model realizations—143 simulated eruption cases—volcanic cooling produced Indian Ocean and wind responses that temporarily opposed the usual Pacific connection. The observed Pacific-to-Indian basin-mode relationship during 1945–2025 was also exceptional relative to comparable intervals in the millennium-scale simulations, consistent with greenhouse-driven Indian Ocean warming overwhelming the usual Pacific influence.
Key results from the tested systems
proxy records
Thirty-five corals, three tree-ring series and one cave record supported the reconstructions.
annual reconstruction
The three Indo-Pacific indices were reconstructed across 360 years.
modeled eruption cases
Eleven large eruptions were sampled across 13 ensemble members.
modern interval
Observed basin-mode coupling was exceptional in the millennium-scale comparison.
How the research worked
The team reconstructed the Pacific Walker circulation, Indian Ocean Walker circulation and Indian Ocean basin-wide temperature mode from 39 paleoclimate series. The annual records covered 1631–1990 and were checked against instrumental sea-surface temperatures from 1881 onward. They compared 40- and 80-year relationships, repeated the reconstruction with a data-assimilation method, and analyzed a 13-member Community Earth System Model last-millennium ensemble containing all major forcings and volcano-only experiments.
How to interpret this design
The result is conditional on the model structure, inputs, boundary conditions and scenarios chosen by the researchers. Agreement with known observations strengthens confidence, but a projection is not a direct observation of the future or the inaccessible past.
The evidence is produced by computation rather than direct experimental manipulation of the target system. Its value depends on transparent assumptions, realistic inputs, sensitivity testing and comparison with independent observations.
What strengthens or limits the finding?
Multiple proxy types, annual reconstructions, instrumental validation, alternative reconstruction methods and forced climate-model ensembles converge on the disrupted coupling. Proxy coverage remains sparse and uneven, while attribution of a complex ocean-atmosphere relationship depends partly on model assumptions.
The result is meaningfully informative, but identifiable limitations could alter the size, reach or causal interpretation of the finding.
Funding and disclosure context
The recorded funding source is: U.S. National Science Foundation grants OCE-2303513 and AGS-2503122, the WHOI Investment in Science Program and the WHOI Academic Programs Office. The recorded conflict information is: The authors declared no competing interests. Funding or a disclosed relationship does not by itself invalidate a result, but it is relevant when judging design choices, analysis and the need for independent replication.
What it means
Indian Ocean climate cannot always be predicted from Pacific behavior in the same way. Because these links help shape rainfall, heat and marine conditions around densely populated regions, forecasting and risk planning may need to account explicitly for both volcanic shocks and a warming background climate.
Deeper analysis
Coupling is a statistical relationship
The study tracks whether large-scale Pacific and Indian Ocean patterns tend to vary together over decades. A weaker correlation does not mean water stops moving between basins; it means one index has become a less reliable guide to another.
Volcanoes can push both basins at once
Stratospheric aerosols reduce incoming sunlight, but cooling is not spatially uniform. The simulations produced wind and temperature patterns that opposed the oceans’ usual teleconnection, especially after the largest eruptions.
The modern departure has a different signature
Recent Indian Ocean basin warming persisted even when Pacific behavior would normally favor a different response. The paper interprets this as greenhouse forcing increasingly dominating the basin-wide temperature pattern.
Reconstruction agreement is not perfect knowledge
The main result survived a second reconstruction method and multiple window lengths, which strengthens it. Yet every pre-instrumental index remains an estimate built from environmental archives rather than a historical thermometer grid.
What it does NOT prove
- It does not show that volcanic eruptions and greenhouse warming disrupt the oceans through identical mechanisms.
- It does not predict a specific drought, flood, monsoon season or fishery outcome.
- It does not establish that every short period of weak coupling is externally forced.
- It does not reconstruct direct atmospheric measurements before the instrumental era.
- It does not mean the Pacific and Indian Oceans have become permanently independent.
Important limitations
- Only 39 proxy records informed three vast tropical-ocean regions, and their spatial and temporal coverage was uneven.
- Corals, tree rings and cave deposits respond to local environments as well as the large-scale climate modes being reconstructed.
- The annual series ended in 1990, so the latest comparison relies on instrumental observations and model context rather than proxies.
- Filtering and selecting 40- or 80-year windows can affect estimated coupling strength, even though the authors tested alternative windows.
- A climate-model ensemble samples many plausible histories but cannot reproduce every real-world eruption, ocean state or forcing exactly.
- The modern attribution is strongest for the basin-wide Indian Ocean warming relationship; the Indian Ocean Walker circulation response was less consistent.
How this fits with previous research
El Niño and Pacific Walker circulation changes are known to influence Indian Ocean temperatures and winds, and earlier work linked recent basin-wide Indian Ocean warming to greenhouse forcing. Paleoclimate studies also showed that volcanoes can alter tropical circulation. The new analysis joins these strands by reconstructing both basins with mostly marine proxies and testing the coupling itself over centuries and model ensembles.
Questions still unanswered
- How will continued warming change the strength and predictability of each Indo-Pacific connection?
- Can additional Indian Ocean corals and other marine archives reduce regional reconstruction uncertainty?
- How do eruption latitude, sulfur injection and the ocean’s starting state determine the size and duration of decoupling?
- What do weaker basin links mean for seasonal forecasts around Africa, Asia and Australia?
- Will newer climate-model ensembles reproduce the same modern exception and its regional consequences?
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Volcanoes once disrupted Indian–Pacific climate links; modern warming is doing so differently
This review was developed from the source record below and, when separately available, the primary paper or government report. The summary and analysis on this page are original editorial writing.
- Source organization
- Woods Hole Oceanographic Institution
- Source type
- Scientific organization
- Authors
- Shawn Wang, Delia W. Oppo and Caroline C. Ummenhofer
- Journal / report
- Nature Communications
- Publication date
- August 26, 2026
- DOI
- 10.1038/s41467-026-76705-y
- PMID
- Not available
- Institution
- Woods Hole Oceanographic Institution, MIT-WHOI Joint Program and the Cooperative Institute for Research in Environmental Sciences at the University of Colorado Boulder
- Funding
- U.S. National Science Foundation grants OCE-2303513 and AGS-2503122, the WHOI Investment in Science Program and the WHOI Academic Programs Office
- Conflicts
- The authors declared no competing interests
- Open access
- Yes
- Reuse approach
- Methods and results summarized independently from Woods Hole Oceanographic Institution and the open peer-reviewed article; no press-release wording, source figures, tables, photographs or illustrations reproduced.
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