Plausible 2005–2050 emissions scenarios project between 2 °C and 3 °C of warming by 2100
Bibliographic record
Abstract
Abstract Emissions scenarios used by the Intergovernmental Panel on Climate Change (IPCC) are central to climate change research and policy. Here, we identify subsets of scenarios of the IPCC’s 5th (AR5) and forthcoming 6th (AR6) Assessment Reports, including the Shared Socioeconomic Pathway scenarios, that project 2005–2050 fossil-fuel-and-industry (FFI) CO 2 emissions growth rates most consistent with observations from 2005 to 2020 and International Energy Agency (IEA) projections to 2050. These scenarios project between 2 °C and 3 °C of warming by 2100, with a median of 2.2 °C. The subset of plausible IPCC scenarios does not represent all possible trajectories of future emissions and warming. Collectively, they project continued mitigation progress and suggest the world is presently on a lower emissions trajectory than is often assumed. However, these scenarios also indicate that the world is still off track from limiting 21st-century warming to 1.5 °C or below 2 °C.
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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 | 0.001 | 0.002 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.004 | 0.001 |
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".