Decreasing anthropogenic methane emissions in Europe and Siberia inferred from continuous carbon dioxide and methane observations at Alert, Canada
Bibliographic record
Abstract
The rate of increase in global atmospheric methane (CH4) abundance has steadily declined since the late 1980s with near zero increase from 1999 through 2006. At the Canadian Baseline Observatory at Alert, Canada (82°28′N, 62°30′W), continuous measurements of methane (CH4) and carbon dioxide (CO2) have been made since 1987. During winter, both gases are frequently highly correlated during well‐defined episodes lasting from 2 to 5 days. We observe a gradual decrease in the ratios of CH4/CO2 during these episodes from ∼16 ppb CH4 (ppm CO2)−1 to ∼12 ppb CH4 (ppm of CO2)−1 over the entire record. An atmospheric transport model with prescribed CO2 and CH4 source distributions is used to partition simulated CH4 events into contributions by region. We show that anthropogenic emissions from Europe and Siberia account for more than 85% of the CO2 and CH4 enhancements simulated at Alert, but without a change in CH4 emissions, modeled CH4/CO2 ratios remain constant. To reproduce the observed trend in the ratio of CH4/CO2, the model requires a reduction in emissions of CH4 on the order of 30 Tg (13.6 to 33.4 Tg) in Europe and Siberia over the observational period. This is about twice the drop reported by the Emission Database for Global Atmospheric Research (EDGAR) emissions inventory and large enough to account for the leveling off of the global atmospheric CH4 burden observed over the past 20 years.
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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) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.001 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.001 |
| 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".