On the secular trend of CO<i><sub>x</sub></i> and CO<sub>2</sub> in the lower thermosphere
Bibliographic record
Abstract
Abstract An analysis of recent observations (2004–2013) made by the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE‐FTS) instrument indicate that total carbon (COx = CO + CO2) has been increasing rapidly in the lower thermosphere, above 10−3 hPa (90 km). The estimated trend (~9% per decade) is about a factor of 2 larger than the rate of increase that can be ascribed to anthropogenic emissions of CO2 (~5% per decade). Here we investigate whether the observed trends of CO2 and COx can be reproduced using the Whole Atmosphere Community Climate Model (WACCM), a comprehensive global model with interactive chemistry, wherein vertical eddy diffusion is estimated from a parameterization of gravity wave breaking that can respond to changes in the model climate. We find that the modeled trends of CO2 and COx do not differ significantly at any altitude from the value expected from anthropogenic increases of CO2 and that WACCM does not produce significant changes in eddy diffusivity. We show that the discrepancy between model and observations cannot be attributed to uncertainties associated with geophysical noise and instrumental effects, to difficulties separating a linear trend from the 11 year solar signal, or to sparse sampling by ACE‐FTS. Estimates of the impact of vertical diffusion on CO2 in the model indicate that a large increase in Kzz (~30% per decade) would be necessary to reconcile WACCM results with observations. It might be possible to ascertain whether such a large change in vertical mixing has in fact taken place by examining the trend of water vapor in the upper mesosphere.
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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 | 0.001 |
| 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".