Observation-Based Emission Estimates of the Potent Greenhouse Gas HFC-23 for Article 5 and Non-Article 5 Country Groups under the Montreal Protocol

The Kigali Amendment to the Montreal Protocol requires parties to destroy, to the extent practicable, HFC-23 generated as a byproduct during the production of controlled hydrochlorofluorocarbons and…

By Hu, Vollmer, Reimann +11Environmental Science & TechnologyOct 27, 2026

Score████░░░░░░4.3

VerdictWorth a reader's time today.

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Abstract

Abstract The Kigali Amendment to the Montreal Protocol requires parties to destroy, to the extent practicable, HFC-23 generated as a byproduct during the production of controlled hydrochlorofluorocarbons and hydrofluorocarbons. Global total HFC-23 emissions estimated from reported abatement and known sources (bottom-up) agreed with those inferred from atmospheric observations (top-down) before 2015, but have been substantially lower since then. Here, we show that during 2011–2013, bottom-up estimates of global total HFC-23 emissions were right for the wrong reasons: bottom-up estimates for the non-Article 5 (mainly developed) country group were lower than top-down estimates (1.7 ± 0.2 vs 3.1 ± 0.5 Gg yr–1 on average), while those for the Article 5 (mainly developing) country group were higher (11.8 ± 0.4 vs 9.7 ± 1.0 Gg yr–1), resulting in a cancellation at the global scale. We further show that during 2015–2023, while the underestimation of global bottom-up emissions was dominated by the Article 5 country group, the non-Article 5 country group also contributed in 2023 [bottom-up (byproduct emissions reported to UNEP plus other known sources) vs top-down: 0.5 ± 0.2 vs 1.3 ± 0.6 Gg yr–1]. Our results underscore improvement of emission accounting and mitigation for both country groups under the Kigali Amendment.

Xiaoyi Hu, Martin K. Vollmer, Stefan Reimann, Jens Mühle, Paul B. Krummel, Dickon Young, Chris Lunder, Simon O’Doherty, Christina M. Harth, Peter K. Salameh, Matthew Rigby, Ray F. Weiss, Ronald G. Prinn, Xuekun Fang

The editor's rubric

Heuristic review

Leverage3 / 5: A method or resource many groups across the field will adopt within a year.; 16% of this desk’s rubric
Magnitude3 / 5: Large gain: roughly 2x, or a clear new state of the art on a hard, unsaturated problem.; 20% of this desk’s rubric
Evidence3 / 5: Solid: multiple benchmarks or cohorts, ablations, fair baselines, released code or data.; 20% of this desk’s rubric
Novelty2 / 5: A new combination of known ideas.; 10% of this desk’s rubric
Trajectory2 / 5: Some room to improve with obvious engineering.; 14% of this desk’s rubric
Stakes3 / 5: Meaningful benefit to many people within a few years.; 20% of this desk’s rubric

Dimension	Level	Weight	What that level means
Leverage	███░░3/5	16%	A method or resource many groups across the field will adopt within a year.
Magnitude	███░░3/5	20%	Large gain: roughly 2x, or a clear new state of the art on a hard, unsaturated problem.
Evidence	███░░3/5	20%	Solid: multiple benchmarks or cohorts, ablations, fair baselines, released code or data.
Novelty	██░░░2/5	10%	A new combination of known ideas.
Trajectory	██░░░2/5	14%	Some room to improve with obvious engineering.
Stakes	███░░3/5	20%	Meaningful benefit to many people within a few years.

Editor’s rationale

Heuristic triage from title and abstract text only, not a reading of the paper. Cues found: method (we report); gains (versus baseline); verification (error bars); scale (scalable); stakes (global scale, climate).

How the score was computed

rank-2026-10-18

Score████░░░░░░4.3

Score = 10 × (75% × adjusted merit / 10 + 15% × attention + 10% × freshness)

Desks place stronger verdicts first, then use this score to order work within the same verdict.

Merit: 5.5 / 10; Weighted rubric, evidence-gated.
Adjusted merit: 4.6 / 10; Shrunk toward the desk prior by editor confidence (42%).
Attention: 0%; Citations, upvotes, points, mentions.
Freshness: 85%; Half-life decay since publication.

Citations0 (reference 15, via openalex, Oct 29, 2026, 07:29 UTC)

The record

Reviewed by heuristic-v10 on Oct 29, 2026, 07:29 UTC. Paper type: method.
Categories: Atmospheric Ozone and Climate, Atmospheric and Environmental Gas Dynamics, Atmospheric chemistry and aerosols, Atmospheric Science, Earth and Planetary Sciences
TOP, No.5 in the Climate & Energy edition of October 29, 2026.