Long‐term trends of inorganic chlorine from ground‐based infrared solar spectra: Past increases and evidence for stabilization
Bibliographic record
Abstract
Long‐term time series of hydrogen chloride (HCl) and chlorine nitrate (ClONO 2 ) total column abundances has been retrieved from high spectral resolution ground‐based solar absorption spectra recorded with infrared Fourier transform spectrometers at nine NDSC (Network for the Detection of Stratospheric Change) sites in both Northern and Southern Hemispheres. The data sets span up to 24 years and most extend until the end of 2001. The time series of Cl y (defined here as the sum of the HCl and ClONO 2 columns) from the three locations with the longest time‐span records show rapid increases until the early 1990s superimposed on marked day‐to‐day, seasonal and inter‐annual variability. Subsequently, the buildup in Cl y slows and reaches a broad plateau after 1996, also characterized by variability. A similar time evolution is also found in the total chlorine concentration at 55 km altitude derived from Halogen Occultation Experiment (HALOE) global observations since 1991. The stabilization of inorganic chlorine observed in both the total columns and at 55 km altitude indicates that the near‐global 1993 organic chlorine (CCl y ) peak at the Earth's surface has now propagated over a broad altitude range in the upper atmosphere, though the time lag is difficult to quantify precisely from the current data sets, due to variability. We compare the three longest measured time series with two‐dimensional model calculations extending from 1977 to 2010, based on a halocarbon scenario that assumes past measured trends and a realistic extrapolation into the future. The model predicts broad Cl y maxima consistent with the long‐term observations, followed by a slow Cl y decline reaching 12–14% relative to the peak by 2010. The data reported here confirm the effectiveness of the Montreal Protocol and its Amendments and Adjustments in progressively phasing out the major man‐related perturbations of the stratospheric ozone layer, in particular, the anthropogenic chlorine‐bearing source gases.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".