The United States “warming hole”: Quantifying the forced aerosol response given large internal variability
Bibliographic record
Abstract
Abstract Twenty‐five years of large summer cooling over the southeastern United States ending in the mid‐1970s coincided with rapidly increasing anthropogenic aerosol emissions. Here we assess the claim that the cooling in that period was predominantly due to such aerosols. We utilize two 50‐member sets of coupled climate model simulations, one with only anthropogenic aerosol forcings and another with all known natural and anthropogenic forcings, together with a long control integration. We show that, in the absence of aerosol forcing, none of the model simulations capture the observed surface cooling rate (∼0.56°C decade−1), whereas with increasing aerosol emissions 2 (of 50) of the simulations do. More importantly, however, we find that the cooling from aerosols (0.20°C decade−1) is insufficient to explain the observation. Our results therefore suggest that, while aerosols may have played a role, the observed cooling was a rare event that contained a large contribution from unforced internal 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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.001 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.001 | 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".