Millennial‐scale temperature variations in North America during the Holocene
Bibliographic record
Abstract
A mean continental July temperature reconstruction based on pollen records from across North America quantifies temperature variations of several timescales for the past 14,000 cal yr BP. In North America, temperatures increased nearly 4°C during the late glacial, reaching maximum values between 6000 and 3000 cal yr BP, after which mean July temperatures decreased. Superimposed on this orbital‐scale trend are millennial‐scale temperature variations that appear coherent in structure and frequency with high‐resolution ice, marine and other terrestrial paleoclimate records of the Holocene. During the Holocene, climate in North America appears to have varied periodically every ∼1100 years rather than the ∼1500 year cycle found during the last glacial period. Coherence at frequencies between 900 and 1100 years between land, ice, and ocean records suggests a common forcing associated with widespread surface impacts during the Holocene. These results provide important insight to the global warming debate, as the observed twentieth century temperature increase appears unprecedented compared to our mean North American temperature reconstruction of the past 14,000 years.
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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 | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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".