Interhemispheric monsoon dynamics over the past 450,000 years

Original title: Interhemispheric monsoon dynamics over the past 450,000 years.

The global monsoon system provides freshwater to much of Earth's biota, including its human population1.

By Olson, Gillikin, Parmenter +9NatureOct 14, 2026

Score████░░░░░░4.3

VerdictWorth a reader's time today.

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Abstract

The global monsoon system provides freshwater to much of Earth's biota, including its human population1. The Milankovitch theory predicts changes in Earth's solar insolation over geologic time, and these variations are expected to result in changes to the global monsoon2. Internal climate forcings, such as ice cover and sea surface temperatures, may also affect the system. However, few records of monsoon variability in the Southern Hemisphere over glacial-interglacial cycles exist to test our understanding of the factors that drive variations in the global monsoon. Here we show that monsoons in both the Southern and Northern Hemispheres vary with Milankovitch forcing, and with internal boundary conditions over the past 450,000 years. We present a record of South American Summer Monsoon (SASM) variability, based on speleothem oxygen-isotope data from the Amazon Basin. South American Summer Monsoon variability and that of a major Northern Hemisphere monsoon-that is, the Asian monsoon3,4-have been strikingly out of phase. However, we observe occasional synchronous behaviour in regions impacted by both monsoons. We identify a synchronicity threshold that is exceeded during ten events, including during glacial terminations. Comparison with palaeoclimatic forcing factors during these intervals indicates that greenhouse gas concentrations, cross-equatorial thermal gradients and sea surface temperatures in both the Atlantic and Pacific probably influence these events. This record demonstrates that the global monsoon can reorganize itself, especially during intervals of rapidly changing planetary boundary conditions.

E J Olson, D P Gillikin, D Parmenter, S Burns, A Verheyden, O Miyawaki, M Vuille, L F Piccirillo, R Castro, G Yurivilca, R L Edwards, D T Rodbell

The editor's rubric

Heuristic review

Leverage3 / 5: A method or resource many groups across the field will adopt within a year.; 16% of this desk’s rubric
Magnitude3 / 5: Large gain: roughly 2x, or a clear new state of the art on a hard, unsaturated problem.; 20% of this desk’s rubric
Evidence3 / 5: Solid: multiple benchmarks or cohorts, ablations, fair baselines, released code or data.; 20% of this desk’s rubric
Novelty4 / 5: Challenges a prevailing assumption with evidence.; 10% of this desk’s rubric
Trajectory2 / 5: Some room to improve with obvious engineering.; 14% of this desk’s rubric
Stakes3 / 5: Meaningful benefit to many people within a few years.; 20% of this desk’s rubric

Dimension	Level	Weight	What that level means
Leverage	███░░ 3	16%	A method or resource many groups across the field will adopt within a year.
Magnitude	███░░ 3	20%	Large gain: roughly 2x, or a clear new state of the art on a hard, unsaturated problem.
Evidence	███░░ 3	20%	Solid: multiple benchmarks or cohorts, ablations, fair baselines, released code or data.
Novelty	████░ 4	10%	Challenges a prevailing assumption with evidence.
Trajectory	██░░░ 2	14%	Some room to improve with obvious engineering.
Stakes	███░░ 3	20%	Meaningful benefit to many people within a few years.

Editor’s rationale

Heuristic triage from title and abstract text only, not a reading of the paper. Cues found: method (we propose, we report); gains (outperforms); novelty (open problem, discovery); stakes (global scale, energy, climate).

How the score was computed

rank-2026-10-18

Score████░░░░░░4.3

Score = 10 × (75% × adjusted merit / 10 + 15% × attention + 10% × freshness)

Desks place stronger verdicts first, then use this score to order work within the same verdict.

Merit: 5.9 / 10; Weighted rubric, evidence-gated.
Adjusted merit: 4.9 / 10; Shrunk toward the desk prior by editor confidence (46%).
Attention: 0%; Citations, upvotes, points, mentions.
Freshness: 65%; Half-life decay since publication.

Citations0 (reference 15, via openalex, Oct 20, 2026, 07:29 UTC)

The record

Reviewed by heuristic-v7 on Oct 20, 2026, 07:29 UTC. Paper type: method.
Categories: Journal Article
TOP, No.6 in the Climate & Energy edition of October 20, 2026.