Improved Comparability and System-Wide Verification to Support a Scalable Carbon Credit Market

Lamarque, ﻿Jean-Francois; Friedlingstein, Pierre; Osias, Brian; Strongin, Steve; Balaji, Venkatramani; Bowman, Kevin W.; Canadell, Josep G.; Ciais, Philippe; Cullen, Heidi; Davis, Kenneth J.; Doney, Scott C.; Gurney, Kevin R.; Karspeck, Alicia R.; Koven, Charles D.; McKinley, Galen; Peters, Glen P.; Pongratz, Julia; Stephens, Britt; Sweeney, Colm

doi:10.5194/egusphere-2025-6457

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https://doi.org/10.5194/egusphere-2025-6457

Preprints

04 Jan 2026

| 04 Jan 2026

Improved Comparability and System-Wide Verification to Support a Scalable Carbon Credit Market

Jean-Francois Lamarque, Pierre Friedlingstein, Brian Osias, Steve Strongin, Venkatramani Balaji, Kevin W. Bowman, Josep G. Canadell, Philippe Ciais, Heidi Cullen, Kenneth J. Davis, Scott C. Doney, Kevin R. Gurney, Alicia R. Karspeck, Charles D. Koven, Galen McKinley, Glen P. Peters, Julia Pongratz, Britt Stephens, and Colm Sweeney

Abstract. Achieving net-zero emissions over the coming decades requires unprecedented reductions in anthropogenic emissions of greenhouse gases (GHGs) complemented by a rapid ramp-up in the magnitude of global carbon dioxide removal (CDR). The carbon credit market (CCM) is emerging as a means to finance both emissions reductions and carbon dioxide removal from the atmosphere. To achieve necessary growth on these fronts, the total scope and diversity of projects that are candidates for inclusion in the CCM must expand, necessitating a means of comprehensively assessing the quality of carbon credit projects (CCPs) based on their ability to make quantifiable reductions to GHG concentrations in the atmosphere. Toward a comprehensive quality assessment, we propose a framework to assess and differentiate CCPs based on their estimated impact on atmospheric GHG composition. In parallel, we propose a path towards verification of the aggregated atmospheric impact of CCM actions, since a detectable and attributable signal in atmospheric GHG composition can be viewed as the clearest measure of their climate forcing and, therefore, effectiveness.

Received: 23 Dec 2025 – Discussion started: 04 Jan 2026

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RC1:
'Comment on egusphere-2025-6457', Xueyuan Gao, 11 Mar 2026
This Perspective proposes a conceptual framework—the Atmospheric Impact Framework (AIF)—to evaluate carbon credit projects based on their measurable impact on atmospheric greenhouse gas concentrations. The paper argues that the ultimate test of carbon credit effectiveness should be observable changes in atmospheric GHG composition and proposes combining atmospheric observations, modeling systems, and risk-adjusted accounting to compare heterogeneous carbon credit types. The authors bring together expertise from atmospheric science, Earth system modeling, and carbon cycle research, and the paper offers an important high-level scientific perspective linking atmospheric monitoring infrastructure to carbon market integrity. The proposal to connect bottom-up MRV approaches with top-down atmospheric verification is particularly compelling and aligns with ongoing efforts to improve transparency in the voluntary carbon market.

I have some specific comments:
The paper would benefit from clearer positioning relative to existing MRV frameworks and carbon credit integrity initiatives (e.g., ICVCM, rating agencies, or registry methodologies). Strengthening the connection between the proposed atmospheric verification system and the practical realities of project-level carbon accounting would significantly improve the manuscript’s impact. The authors should clarify: whether the proposed system is intended to validate the overall carbon market rather than individual projects, and how atmospheric observations would interact with existing project-scale MRV systems.

The discussion notes that even the COVID-19 emissions reduction (~2.6 GtCO2) was difficult to detect in global atmospheric CO2 records due to natural variability. This raises an important question: what level of carbon project deployment would produce a detectable atmospheric signal? While the manuscript mentions a potential threshold of ~1 GtCO2 per year, the paper would benefit from quantitative estimates of detection limits, discussion of signal-to-noise ratios in regional inversion systems, and examples of regions where detection may already be feasible.

The manuscript occasionally uses both “carbon credit market (CCM)” and “voluntary carbon market” interchangeably. I suggest using voluntary carbon market throughout the manuscript. In addition, the abbreviation CCPs may create confusion because in the carbon market context it commonly refers to the Core Carbon Principles (CCPs) developed by ICVCM. For example, in Line 60, readers may interpret the sentence as referring to the difficulty of assessing the quality of the Core Carbon Principles themselves, whereas the authors actually intend to refer to carbon projects. I recommend replacing “CCPs” with carbon projects throughout the manuscript.
Citation: https://doi.org/10.5194/egusphere-2025-6457-RC1
RC2:
'Comment on egusphere-2025-6457', Anonymous Referee #2, 27 May 2026
This manuscript proposes the atmospheric impact framework (AIF), a new metric for "estimating the risk that the reported amount of carbon credits will not be delivered as promised, owing either to errors in the initial quantification or in estimates of permanence." The paper goes on to describe a series of parallel community actions that could aid in the implementation of the AIF, in addition to supporting consensus development for the CDR community as a whole. These include pilot assessments for AIF quantification, regional carbon budget analyses that assess both the AIF, the counterfactual baseline, and rates of natural and anthropogenic change expected in the counterfactual baseline. The authors suggest that these improvements can be translated to support the quantification of the Global Carbon Budget, including both the Earth System Models and observing systems that support the Global Carbon Budget, and National carbon inventories.
While much of the background information for the carbon budget is adequately described and certainly elucidates the need for an AIF-type metric, in general the discussion of the AIF itself is minimal. While the authors provide a robust summary of COVID-driven emissions reductions as a way of scaling the problem, this case study does not by itself show the potential value or impact of the AIF in solving this problem. In my view, the manuscript could have been substantially improved through the inclusion of even a hypothetical case study that showed the value of the AIF framework. Narratively, the authors spend so much time setting up the AIF that to end the main body of the paper without showcasing the applications of the AIF more seemed somewhat anticlimactic. A simple back-of-the-envelope case study or application of the AIF would fill this key gap.
Without a real sense of how the AIF could be applied or a demonstration of its potential impact in a clear case study, it is difficult to assess whether the following suggested actions are justified. While the list is logical (if ambitious) assuming that the AIF becomes a key assessment metric, a research-based assessment of the AIF seems warranted first.
Alternatively, if the authors intended the AIF not to be the central tenet of this perspective piece but one of multiple recommendations (e.g., regional assessments being another key factor), the organization of Section 2 could have supported this more clearly. After all, the AIF does not appear in the title or in the abstract. Further, the following list of actions is more expansive than simple discussion of the AIF.
Minor Comments.
The authors switch back and forth between the use of the plural inclusive to indicate the authors of this perspective piece and the members of the scientific community as a whole. The use of the plural inclusive may be appropriate for perspective pieces, though it helps to be consistent (my personal preference is to write as We the Authors, and identify actions for the scientific community by name).

Lines 147-155. Does the AIF replace or modify our assessments of permanence, leakage, additionality? Are some of those assessments included in the AIF? Is the AIF additional to those assessments? How does the AIF interact with other discounting metrics already applied? Is there any risk or value of double-counting or in this case, double-discounting? Again a case study showing how the AIF is applied to a single CCP or an aggregate set of CCPs would have been valuable.

Line 170. “we anticipate that the AIF analysis will require periodic reevaluation…” Do you mean the equation itself will require reevaluation, or the definition of I, or simply the quantification of the AIF for each CCP will need to be consistently reevaluated? (Seems obvious that it would be the latter, but the language isn’t clear).
Citation: https://doi.org/10.5194/egusphere-2025-6457-RC2

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Jan 2026	1,228	583	54	1,865
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Apr 2026	94	71	0	165
May 2026	55	90	4	149
Jun 2026	9	1	2	12

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Short summary

This Perspective highlights requirements to scale the carbon credit market and enable the growth in climate solutions funded through such market. The requirements are on the understanding of the value of the proposed carbon credit projects, and on the availability of a verification system. This verification becomes particularly relevant as the carbon credit market scales to significant impacts on CO₂ (or other greenhouse gases), such that attribution to collective actions can be identified.


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