Paleoclimate
Maya rainfall became harder to forecast after 500 CE
Open access · cc by · source: Europe PMC
A Belize speleothem shows seasonal rainfall predictability collapsing after 500 CE and bottoming in the Terminal Classic, alongside drought.
How this study connects
Role on claims
Each row is a claim on a concept or method page where this paper supports, challenges, or qualifies the statement. Roles are hand-checked — not a model guess.
This library holds 9 empirical papers on paleoclimate with measured outcomes rather than reviews.
Evidence for the claim as stated.
A Belize speleothem shows seasonal rainfall predictability collapsing after 500 CE and bottoming in the Terminal Classic, alongside drought.
Evidence for the claim as stated.
Not every 'ensemble' in the index is a climate GCM. Six hundred three Glimmer-CISM ice-sheet experiments mixed FAMOUS and CCSM3 climates; a COPRA age-model ensemble on a Belize speleothem measured seasonal predictability, not atmospheric initial-condition spread. Those are ensembles of a different model class.
Evidence for the claim as stated.
The third index paper is not a ¹⁴C study. Ensemble COPRA age models, wavelets and recurrence plots on sub-annually resolved Yok Balum YOK-G δ¹³C (and δ¹⁸O) show drying from ~500 CE, peaking 700–900 CE, and seasonal predictability τpred falling below significance between 800 and 1000 CE. Toy-model tests show sampling resolution cannot explain most of the drop. Societal collapse is correlated, not proven causal. COPRA is an ensemble of speleothem age models (2σ ≈ 5 years in that paper), not a ¹⁴C measurement.
Evidence for the claim as stated.
¹⁴C years and COPRA speleothem years are different clocks. The permafrost papers report uncalibrated ¹⁴C ages and F¹⁴C/Δ¹⁴C on organic carbon. The Maya paper ensembles age models of cave calcite to date a rainfall-seasonality collapse. Treating τpred < significance in 800–1000 CE as a radiocarbon date of Classic Maya drought is a category error, even though the index lists the paper under this method.
Evidence for the claim as stated.
Open questions
Tensions this paper is part of
From concept pages' “where studies disagree.” Disagreement means the same question; scope means different assays, populations, or outcomes.
¹⁴C years and COPRA speleothem years are different clocks. The permafrost papers report uncalibrated ¹⁴C ages and F¹⁴C/Δ¹⁴C on organic carbon. The Maya paper ensembles age models of cave calcite to date a rainfall-seasonality collapse. Treating τpred < significance in 800–1000 CE as a radiocarbon date of Classic Maya drought is a category error, even though the index lists the paper under this method.
Study at a glance
- Design
- Other — Sub-annual speleothem δ13C analysis of seasonal rainfall predictability over 1600 years
- N
- Single Yok Balum YOK-G speleothem record spanning ~1600 years
- Population
- Seasonal hydroclimate recorded in Yok Balum Cave, Belize
- Outcome
- Collapse of seasonal rainfall predictability during the Terminal Classic drought
Structured fields used in claim comparison tables when every cited study has a complete layer.
Inspect source passages
Maya rainfall became harder to forecast after 500 CE
These passages occur verbatim in the stored paper text. They support the points listed below; they do not verify every statement in the explanation.
Why use δ13C rather than δ18O for local seasonality?
We focus on speleothem δ 13 C as a proxy for local hydroclimate at seasonal scale near Maya sociopolitical centres whereas the oxygen isotope signal integrates more distal dynamics, reflecting convective activity strength, source moisture location, moisture path length, and local rainfall amount.
When does YOK-G show drying?
The YOK-G δ 13 C record suggests a persistent drying trend initiated in 500 CE towards pronounced dry conditions between 600-800 CE.
Key findings
Drying began ~500 CE and peaked 700–900 CE. Seasonal predictability τpred fell below significance between 800 and 1000 CE, after an earlier decline from 500 CE. Toy-model tests show sampling resolution cannot explain most of the drop. Predictability later recovered ~1050–1200 CE.
Methodology
Authors ran ensemble COPRA age models, wavelets, and recurrence plots on sub-annually resolved Yok Balum YOK-G δ13C (and δ18O) to measure seasonal-cycle strength and year-to-year predictability over 1600 years.
Limitations
Speleothem δ13C mixes infiltration, PCP, and cave processes; societal collapse is correlated, not proven causal; a one-year drought crop-loss figure is from an ecological scenario, not the cave record itself.
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