El Niño's tropical climate and teleconnections as a blueprint for pre‐Ice Age climates
Bibliographic record
Abstract
At ∼2.7 million years ago the warm equable climates of early and “middle” Pliocene time (used here to mean from ∼5 to ∼2.7 Ma) were replaced by recurring ice ages. Most attempts to explain the change appeal either to changes in CO 2 in the atmosphere or reduced heat transport by the Atlantic Ocean. The sources of the strongest teleconnections in the current climate, however, lie in the tropics, and such connections occur by transport of heat and moisture by the atmosphere. The most prominent of these teleconnections link aberrations in sea surface temperatures in the equatorial Pacific, El Niño–Southern Oscillation (ENSO) variations, with warm and dry or cool and wet anomalies in extratropical climates. We show that in most cases early and middle Pliocene climate both in equatorial regions and in the extratropics differ from present‐day climates with the same spatial pattern as that associated with ENSO. For instance, not only was Canada warmer during early Pliocene time than at present, as it is during El Niño, but the region surrounding the Gulf of Mexico appears to have been cooler and a bit wetter, as it commonly is during El Niño. A virtually permanent El Niño‐like state appears to have characterized pre‐Ice Age climates, suggesting that transport of heat by the atmosphere was the principal mechanism that maintained extratropical warmth. Accordingly, cooling and the growth of recurring ice sheets in the Northern Hemisphere resulted from the development of a strong Walker circulation and a weakening of the Hadley circulation.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".