Atmospheric histories of halocarbons from analysis of Antarctic firn air: Major Montreal Protocol species
Bibliographic record
Abstract
Air samples extracted from Antarctic firn at Law Dome have been analyzed for the suite of halocarbons that contribute most of the anthropogenic chlorine and about half the anthropogenic bromine presently released into the stratosphere. The species, all included in the Montreal Protocol, are the chlorofluorocarbons (CFCs ‐11, ‐12, ‐113, ‐114, ‐115), hydrochlorofluorocarbons (HCFCs ‐22, ‐141b, ‐142b), halons (H ‐1211, ‐1301), CH 3 CCl 3 (methyl chloroform) and CCl 4 (carbon tetrachloride). The measurements were used to reconstruct the atmospheric history of these species since the 1930s, providing a record considerably predating existing in situ records or other conventional air archives, encompassing virtually the entire history of anthropogenic emissions of CFCs, HCFCs, and halons and giving early 20 th century levels for CH 3 CCl 3 and CCl 4 . Significant features of this study are (1) the narrow age spread (spectral width 5 years) of the individual firn air samples, which reveals rapid atmospheric changes, (2) the use of inversion techniques to infer past atmospheric composition with associated uncertainties, and (3) the low analytical detection limit (<0.1 ppt), which, together with the narrow air age spread, detects early background levels and resolves the time that industrial emissions first appeared in the southern hemisphere atmosphere. Integrity of the data is demonstrated by successful intercomparison of data from independent firn sites on Law Dome with common time‐series. An upper limit is given for the potential contribution to atmospheric levels of CH 3 CCl 3 from nonindustrial sources. The atmospheric records produced from firn air are compared to calculations based on the history of their global emissions.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.000 | 0.002 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.012 | 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 teacher head, 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".