Fairly Sharing 1.5: National Fair Shares of a 1.5°C-Compliant Global Mitigation Effort
Bibliographic record
Abstract
The problem of fairly distributing the global mitigation effort is particularly important for the 1.5°C temperature limitation objective, due to its rapidly depleting global carbon budget. Here, we present methodology and results of the first study examining national mitigation pledges presented at the 2015 Paris climate summit, relative to equity benchmarks and 1.5°C-compliant global mitigation. Uniquely, pertinent ethical choices were made via deliberative processes of civil society organizations, resulting in an agreed range of effort-sharing parameters. Based on this, we quantified each country’s range of fair shares of 1.5°C-compliant mitigation, using the Climate Equity Reference Project’s allocation framework. Contrasting this with national 2025/2030 mitigation pledges reveals a large global mitigation gap, within which wealthier countries’ mitigation pledges fall far short, while poorer countries’ pledges, collectively, meet their fair share. We also present results for individual countries (e.g. China exceeding; India meeting; EU, USA, Japan, and Brazil falling short). We outline ethical considerations and choices arising when deliberating fair effort sharing and discuss the importance of separating this choice making from the scholarly work of quantitative ‘‘equity modelling’’ itself. Second, we elaborate our approach for quantifying countries’ fair shares of a global mitigation effort, the Climate Equity Reference Framework. Third, we present and discuss the results of this analysis with emphasis on the role of mitigation support. In concluding, we identify twofold obligations for all countries in a justice-centred implementation of 1.5°C-compliant mitigation: (1) unsupported domestic reductions and (2) engagement in deep international mitigation cooperation, through provision of international financial and other support, or through undertaking additional supported mitigation activities. Consequently, an equitable pathway to 1.5°C can only be imagined with such large-scale international cooperation and support; otherwise, 1.5°C-compliant mitigation will remain out of reach, impose undue suffering on the world’s poorest, or both.
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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 | 0.018 | 0.039 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.003 |
| Scholarly communication | 0.004 | 0.004 |
| Open science | 0.001 | 0.003 |
| Research integrity | 0.001 | 0.002 |
| Insufficient payload (model declined to judge) | 0.006 | 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".