Semi-empirical estimates of stratospheric circulation and the lifetimes of chlorofluorocarbons and carbon tetrachloride
Bibliographic record
Abstract
Abstract Chlorofluorocarbons (CFCs) and carbon tetrachloride (CCl 4 ) are ozone-depleting substances with high radiative efficiencies; however, uncertainties in their atmospheric lifetimes hinder top-down emission monitoring efforts. Here, we compute the loss, emission, and lifetime of CFC-11, CFC-12, and CCl 4 using their mass balance in the stratosphere. We first infer the strength of the stratospheric overturning circulation using satellite measurements of nitrous oxide; the mass flux at about 18 km is then used to compute the loss of CFC-11, CFC-12, and CCl 4 . We confirm that anomalous surface measurements of CFC-11 from 2013 to 2018 cannot be attributed to variability in stratospheric transport alone, and we infer near-steady CCl 4 emissions since 2013. Atmospheric lifetimes (50, 86, and 41 yr) independent of previous work are also computed using loss rates. These estimates add confidence to emission inversions and projections of the compounds’ ozone and climate impacts, and may help detect breaches of the Montreal Protocol.
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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 | 0.002 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 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".