Stratosphere-troposphere coupling under the extreme conditions of the No-Montreal-Protocol scenario
Bibliographic record
Abstract
The Montreal Protocol and its amendments (MPA) have been a major success in preventing serious health damage from the destruction of the stratospheric ozone layer by chlorofluorocarbons (CFCs). Additionally, unabated CFC emissions would have significantly accelerated global warming and affected large-scale tropospheric circulation. CFC-induced ozone depletion would have contributed to global climate change through reduced absorption of UV radiation, resulting in weaker stratospheric circulation, affecting the dynamical coupling to the troposphere. With the Earth System Model SOCOLv4, we study an extreme condition where the MPA is absent to disentangle the radiative and chemical (i.e., ozone-mediated) effects of CFCs and their impacts on stratosphere-troposphere coupling. Our results show that at the end of the 21st century, unabated CFC emissions would have largely destroyed the global ozone layer, which would have strongly affected the large-scale stratospheric and tropospheric circulation. In the stratosphere, contrary to historical ozone destruction, the polar vortices severely weaken due to low-latitude ozone depletion. In the Northern Hemisphere (NH), the weakening of the vortex leads to a pronounced negative phase of the North Atlantic Oscillation (NAO) in boreal winter and spring due to the chemical CFC effect. Similarly, the stratosphere also affects the Southern Annular Mode (SAM) to be in a more negative phase in austral winter and spring. However, tropospheric warming from CFCs largely dominates the overall SAM response to be in a more positive phase, whereas in the NH it compensates for the NAO negative phase. Additionally to the circulation changes, uncontrolled CFC emissions would have led to around 2.5 K additional global surface warming, being partially compensated by a cooling of around 0.6 K due to ozone depletion, leading to an overall warming of around 1.9 K. Our study strongly emphasizes the importance of the MPA for our climate and its mitigation of stratospheric circulation changes and their effects on tropospheric variability.
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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 | 0.001 | 0.002 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.001 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.003 | 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".