Observed and simulated changes in Antarctic sea ice extent over the past 50 years
Bibliographic record
Abstract
Continuous monitoring of the polar regions by satellites has shown that sea ice extent (SIE) in the Antarctic has increased slightly since 1979. By contrast, climate model simulations including all major anthropogenic and natural climate influences simulate an average decrease in SIE since 1979. Here we take a longer view and assess the consistency of observed and simulated changes in Antarctic SIE using recently recovered satellite-based estimates of Antarctic SIE for September 1964 and May–July 1966, hence extending the current observational record from 35 to 50 years. While there is evidence of inconsistency between observed trends in Antarctic SIE and those simulated since 1979, particularly in models with realistic interannual variability, the observed trends since the mid-1960s fall within the 5–95% range of simulated trends. Thus, our results broadly support the hypothesis that the recent increase in Antarctic SIE is due to internal variability, though the reasons for the inconsistency in simulated and observed changes since 1979 remain to be determined.
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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 | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.001 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 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".