Publications & Commentary

Berkeley Carbon Research Articles & Perspectives

Quantifying the additionality of cookstove carbon projects, Annelise Gill-Wiehl, Marie Hogan, Barbara K. Haya. (2026). Carbon Management, DOI: 10.1080/17583004.2026.2618350

UNFCCC Carbon Trading Could Undermine Global Climate Action, Stephen Lezak, Sharaban T. Zaman, Injy Johnstone, Barbara K. Haya. (2025). Nature Climate Change, DOI: 10.1038/s41558-025-02517-5.

Also available at this share link

Funding forests’ climate potential without carbon offsets, Libby Blanchard, Barbara K. Haya, Christa Anderson, Grayson Badgley, Danny Cullenward, Peng Gao, Michael L. Goulden, Jennifer A. Holm, Kimberly A. Novick, Anna T. Trugman, Jonathan A. Wang, Christopher A. Williams, Chao Wu, Linqing Yang, and William R.L. Anderegg. (2024). One Earth. DOI: 10.1016/j.oneear.2024.06.006

Methodological issues with deforestation baselines compromise the integrity of carbon offsets from REDD+, Thales A.P. West, Barbara Bomfim, Barbara K. Haya. (2024). Global Environmental Change. DOI: 10.1016/j.gloenvcha.2024.102863

See the press release

Pervasive over-crediting from cookstove offset methodologies, Annelise Gill-Wiehl, Daniel M. Kammen & Barbara K. Haya. (2024). Nature Sustainainability.  DOI: 10.1038/s41893-023-01259-6. (open access version)

⇒ Coverage by the Financial Times
⇒ Coverage by the Guardian
⇒ Coverage by Heatmap News
⇒ Coverage by AFP News & Barrons
⇒ More media coverage of this article
⇒ See our cookstoves carbon offset project page

Instead of Carbon Offsets, We Need ‘Contributions’ to Forests, Stanford Social Innovation Review, January 31, 2024, by Libby Blanchard, William R.L. Anderegg, Barbara K. Haya. 

Quality Assessment of REDD+ Carbon Credit Projects, Barbara K. Haya, Kelsey Alford-Jones, William R. L. Anderegg, Betsy Beymer-Farris, Libby Blanchard, Barbara Bomfim, Dylan Chin,  Samuel Evans, Marie Hogan, Jennifer A. Holm, Kathleen McAfee, Ivy So, Thales A. P. West, Lauren Withey. (2023, September 15). Berkeley Carbon Trading Project

⇒ Coverage by Bloomberg
⇒ Coverage by the Guardian
⇒ See our REDD+ offset project page

Comprehensive review of carbon quantification by improved forest management offset protocols, Barbara K. Haya, Samuel Evans, Letty Brown, Jacob Bukoski, Van Butsic, Bodie Cabiyo, Rory Jacobson, Amber Kerr, Matthew Potts and Daniel L. Sanchez. (2023). Frontiers in Forests and Global Change. DOI: 10.3389/ffgc.2023.958879

⇒ Coverage by Bloomberg

Managing Uncertainty in Carbon Offsets: Insights from California’s Standardized Approach, Barbara Haya, Danny Cullenward, Aaron L. Strong, Emily Grubert, Robert Heilmayr, Deborah Sivas & Michael Wara. (2020). Climate Policy. DOI: 10.1080/14693062.2020.1781035

⇒ Coverage by MIT Technology Review
⇒ Coverage by KQED
⇒ Earlier working paper version

Carbon Offsets in California: Science in the Policy Development Process, Barbara Haya, Aaron Strong, Emily Grubert, Danny Cullenward. (2016). Book chapter in: In New Trends in Communicating Risk and Resiliency: A Multi-Disciplinary Approach to Global Environmental Change, eds. J. Eichelberger, K. Taylor & Y. Kontar. Springer

Key Research Articles Coauthored by our Team 

Towards more effective nature-based climate solutions in global forests, William R. L. Anderegg, Libby Blanchard, Christa Anderson, Grayson Badgley, Danny Cullenward, Peng Gao, Michael L. Goulden, Barbara Haya, Jennifer A. Holm, Matthew D. Hurteau, Marysa Lague, Meng Liu, Kimberly A. Novick, James Randerson, Anna T. Trugman, Jonathan A. Wang, Christopher A. Williams, Chao Wu & Linqing Yang. (2025). Nature, 643, 1214–1222. https://doi.org/10.1038/s41586-025-09116-6

Systematic assessment of the achieved emission reductions of carbon crediting projects, Benedict S. Probst, Malte Toetzke, Andreas Kontoleon, Laura Díaz Anadón, Jan C. Minx, Barbara K. Haya, Lambert Schneider, Philipp A. Trotter, Thales A.P. West, Annelise Gill-Wiehl, and Volker H. Hoffmann. (2024). Nature Communications, 15, 9562. DOI: 10.1038/s41467-024-53645-z 

Policy challenges to enhance soil carbon sinks: the dirty part of making contributions to the Paris agreement by the United States, Stephen M. Ogle, Richard T. Conant, Bart Fischer, Barbara K. Haya, Dale T. Manning, Bruce A. McCarl, and Tamara Jane Zelikova. (2023). Carbon Management, 14(1). DOI: 10.1080/17583004.2023.2268071

Little evidence of management change in California’s forest offset program, Jared Stapp, Christoph Nolte, Matthew Potts, Matthias Baumann, Barbara K. Haya, and Van Butsic. (2023). Communications Earth & Environment. https://www.nature.com/articles/s43247-023-00984-2
          ⇒ Coverage by Bloomberg

Managing Nature-based Solutions in Fire-prone Ecosystems: Competing Management Objectives in California Forests Evaluated at a Landscape Scale, Claudia Herbert, Barbara K. Haya, Scott L. Stephens, and Van Butsic. (2022). Frontiers in Forests and Global Change. DOI: 10.3389/ffgc.2022.957189

Systematic over-crediting in California’s forest carbon offsets program, Grayson Badgley, Jeremy Freeman, Joseph J. Hamman, Barbara Haya, Anna T. Trugman, William R.L. Anderegg, & Danny Cullenward. (2021). Global Change Biology. DOI: 10.1111/gcb.15943
          ⇒ Paper summary     ⇒ Coverage by ProPublica and MIT Technology Review

Policy Briefs

DEBS in Name Only: Another Way California’s Offset Rule Misses the Mark, Elliot Carleton, Stephen Lezak, Barbara K Haya (August, 2025) 

California sends millions of dollars out of state for carbon offsets of dubious quality, Barbara K Haya & Stephen Lezak (May, 2025; updated June 2025 with a summary for policymakers)

Quality Assessment of Verra’s Updated REDD+ Methodology (VM0048), Barbara K. Haya, Kelsey Alford-Jones, William R. L. Anderegg, Jennifer A. Holm, Thales A. P. West. (July, 2024)

The California Air Resources Board’s US Forest offset protocol underestimates leakage, Barbara Haya. (2019). Goldman School of Public Policy Working Paper

⇒ Haya & Stewart response to comments by the California Air Resources Board  
⇒ Coverage by MIT Technology Review
⇒ Coverage by Berkeley News

Fact Sheets

Fact Sheet: The Size of California’s Carbon Offset Program, last updated June 12, 2018

Fact Sheet: California’s U.S. Forest Offset Protocol Over-credits Reductions, prepared June 6, 2017

California’s Carbon Offsets Program — the Offset Limit Explained. This slide deck visually describes California’s offsets limit, and offers the data tables in a separate tab

Op-Eds

Op-Ed in the San Francisco Chronicle, May 15, 2025, We just found millions in waste in California’s cap-and-trade program. Here’s the fix, by Barbara K Haya & Stephen Lezek 

Op-ed in the New York Times, January 4, 2025, Is America Just Going to Abandon Its Towns Falling Into the Ocean?, by Stephen Lezak

Op-Ed in The Conversation, November 1, 2024, US election: Trump is threatening to turn back the tide on America’s environmental laws and reverse climate progress by Stephen Lezak & Barbara K. Haya

Public Comments & Letters 

Comments to CARB on cap-and-invest workshop, comments by Barbara Haya and Stephen Lezak, November 12, 2025

Comments on Isometric's draft Mangrove Restoration Protocol, submitted to Isometric through their on line form with coauthors Barbara K. Haya, Bhavna Arora, Pamela Castell de Oro Sotelo, Zoe B. Hall, Aliya Khan, Susan Pit, Ando Rabearisoa, Rae Taylor-Burns, Yi Xu, November 1, 2025

Comments on Isometric's draft Environmental and Social Safeguards, comments by Kelsey Alford-Jones submitted to Isometric through their on line form, October 23, 2025

Comments on Washington state’s proposed changes to the U.S. Forest Protocol, Chapter 173-446 WAC, Cap-and-Invest Offsets rulemaking, submitted to the Washington Department of Ecology, August 13, 2025

Integrity Council decision on cookstoves methodologies: an important move towards quality for this important project type, Berkeley Carbon Trading Project Note, published March 20, 2025

Joint Commentary on SBTi’s Discussion Paper: Aligning Corporate Value Chains to Global Climate Goals, specifically on question 13c on the use of Carbon Credits towards company scope 3 targets, submitted to SBTi with coauthors from the University of Utah Wilkes Center for Climate Science and Policy, and University of Oxford's Oxford Net Zero, on October 4, 2024 

Joint Commentary on SBTi’s Discussion Paper: Aligning Corporate Value Chains to Global Climate Goals, specifically on question 13b on the use of Commodity Certificates towards company scope 3 targets, submitted to SBTi with coauthors from the University of Utah Wilkes Center for Climate Science and Policy, and University of Oxford's Oxford Net Zero, on October 4, 2024

Comments on the EU's Technical Assessment on Carbon Removals & Carbon Farming: Forestry, submitted to the European Commission on May 3, 2024

Climate-targets group should rescind its endorsement of carbon offsets, coauthor on Letter to the Editor of Nature. April 30, 2024

Comment on Commodity Futures Trading Commission (CFTC) Guidance Regarding the Listing of Voluntary Carbon Credit Derivative Contracts, RIN 3038–AF40, submitted to the CFTC on February 16, 2024

Comment on Requirements for the development and assessment of Article 6.4 mechanism methodologies and Article 6.4 validation and verification standard for projects, submitted to the UN Article 6.4 Supervisory Body on October 29, 2023

Academic letter in support of AB 1305 and SB 390 (voluntary carbon offsets), submitted to Assembly Member Jesse Gabriel and Senator Monique Limon of the California state legislature on April 17, 2023

Comments to the GHG Protocol on Market-based Accounting Approaches, submitted to the GHG Protocol via their on line survey on March 14, 2023

Comments to the California Air Resources Board on Recommended Changes to its US Forest Projects Offset Protocol, submitted to the California Air Resources Board on December 15, 2022

Comments on the Integrity Council for the Voluntary Offset Market (ICVCM) draft Core Carbon Principles, Assessment Framework, and Assessment Framework, submitted to the ICVCM on September 27, 2022

Comments to the US Securities and Exchange Commission on the proposed offsets provisions under its Proposed Rule on The Enhancement and Standardization of Climate-Related Disclosures for Investors [File No. S7-10-22], submitted to the SEC on June 17, 2022

Comments on the Climate Action Reserve's draft U.S. Landfill Protocol v6.0, submitted to CAR on June 8, 2022

Comments on proposed new VCS methodology - Improved Forest Management through Targeted, Short-Term Harvest Deferral, submitted to Verra on April 22, 2022

Comments on Verra's proposed updates on tonne-year accounting, submitted to Verra on April 8, 2022

Comments on the May 2021 Public Consultation Report of the Taskforce on Scaling Voluntary Carbon Markets (TSVCM), submitted June 21,2021

Public comments submitted on ART TREES 2.0, submitted by Barbara Haya and Matthew D. Potts to Winrock April 2, 2021.

Comments on the Initial Recommendations of the Taskforce on Scaling Voluntary Carbon Markets (TSVCM), submitted to the TSVCM on January 5, 2021.

Comments on ARB’s proposed endorsement of the Tropical Forest Standard: environmental integrity concerns, submitted to the California Air Resources Board on August 29, 2019.

Joint comments on the challenges of monitoring the implementation of California's proposed Tropical Forest Standard, submitted to the California Air Resources Board on August 29, 2019.

Joint comment letter from 110 social and conservation scientists on California’s proposed Tropical Forest Standard (TFS), submitted to the California Air Resources Board on November 14, 2018.

Joint comments submitted to the California Air Resources Board on methods for determining whether offset projects result in Direct Environmental Benefits in the State (DEBS), Submitted July 20, 2018.

Comments submitted to the California Air Resources Board on proposed amendments to the state's cap-and-trade regulation, Submitted May 10, 2018.

Comments submitted to the California Air Resources Board on proposed amendments to the state's cap-and-trade regulation, Submitted Mar. 16, 2018.

Comments submitted to the California Air Resources Board on the state’s draft Climate Change Scoping Plan Update – the proposed strategy for achieving California’s 2030 greenhouse gas target, Submitted Nov. 21, 2016.

Comments submitted to the California Air Resources Board on the state’s proposed REDD program and linkage with Acre, Brazil, Submitted June 4, 2016.

Select Presentations

California's Offsets Program: Outcomes to Date & the Need for Reform, presented by Barbara Haya at the California Environmental Justice Advisory Committee meeting, October 16, 2025, Sacramento, CA

Quality of Carbon Credits & an Alternative Contributions Approach, presented by Barbara Haya at the World Bank ABCDE (Annual Bank Conference on Development Economics) 2025 in the session on Pollution, July 22, 2025, Washington DC

Cap and Trade Reauthorization: Offset Program Reform is Necessary, presented by Barbara Haya at the 2025 California Climate Policy Summit, on the panel, Cap and Trade Reauthorization, Reform, and a Revenue Plan, April, 2025, Sacramento, CA

California’s cap-and-trade and offsets programs – Lessons for Oregon, Presentation to Engineers for a Sustainable Future, co-organized with Center for Sustainable Economy. October 9, 2018. Portland, OR

X