Siti Muinah
GENEVA, May 8 — As the world’s urban centers face an unprecedented confluence of climate-driven threats, the Intergovernmental Panel on Climate Change (IPCC) has officially launched the registration process for Expert Reviewers to evaluate the Second-Order Draft (SOD) of its highly anticipated Special Report on Climate Change and Cities.
This call for participation marks a pivotal stage in the IPCC’s Seventh Assessment Cycle, signaling a rigorous, transparent, and inclusive effort to synthesize the latest scientific knowledge regarding urban resilience, adaptation, and mitigation. With the report scheduled for release in March 2027, the current review period offers a unique window for policymakers and researchers to influence the primary global document designed to guide climate action in the world’s most vulnerable population hubs.
The Mandate for Urban Climate Science
The Special Report on Climate Change and Cities is a landmark endeavor. It stands as the only dedicated special report of the current assessment cycle, underscoring the urgent realization that cities—which house more than half of the global population and account for the majority of global greenhouse gas emissions—are the "frontlines" of the climate crisis.
"Our authors have worked hard to process the tens of thousands of comments received in our First-Order Draft to present a Second-Order Draft that accounts for the suggestions, perspectives, and expertise of urban and climate experts around the world," said Winston Chow, Co-Chair of Working Group II.
Chow emphasized the collaborative nature of this undertaking: "We are proud to present this new draft and would like government representatives and more experts to come forward to review and help us refine the report into one that supports and inspires decision-making on climate action in cities around the world."
A Multi-Stage Journey: The Chronology of Development
The development of an IPCC report is not merely a writing process; it is a marathon of peer review and verification. The current progress follows a strictly defined trajectory:
- January 2025: The Third Lead Author Meeting took place, where teams synthesized the massive feedback from the First-Order Draft.
- October–December 2025: The initial expert review phase saw an overwhelming response, with 1,365 experts submitting over 32,000 individual comments.
- May 8, 2026: Official opening of the Second-Order Draft (SOD) for expert and government review.
- June 26, 2026: Deadline for experts to register for the current review cycle.
- July 3, 2026: Final date for submission of comments on the Second-Order Draft.
- March 2027: Scheduled publication of the final Special Report on Climate Change and Cities.
Following the current review, author teams will integrate the feedback into final drafts. Subsequently, the Summary for Policymakers (SPM)—a condensed, high-level version of the findings—will undergo a final, rigorous line-by-line approval process by member governments, ensuring that the language is both scientifically accurate and politically actionable.
Supporting Data: The Weight of Global Collaboration
The sheer scale of this project is reflective of the global commitment to climate science. During the previous review phase in late 2025, the depth of engagement was historic. With 1,365 registered reviewers providing more than 32,000 comments, the IPCC process ensures that no single perspective dominates.
This multi-stage review process is the bedrock of the IPCC’s credibility. By requiring that every comment be addressed and documented, the organization maintains a standard of objectivity that is unmatched in international policy. These responses, once the report is finalized, are made public, providing a transparent roadmap of how scientific consensus was reached.
The Significance of the Summary for Policymakers (SPM)
A critical addition to the Second-Order Draft is the inclusion of the first draft of the Summary for Policymakers. This document is arguably the most influential product of the IPCC process. While the full report provides the dense technical and scientific basis for climate change impacts and risks, the SPM serves as a strategic manual for municipal leaders, national ministers, and international negotiators.
By distilling complex data on urban heat islands, sea-level rise, infrastructure vulnerability, and sustainable urban planning into concise findings, the SPM bridges the gap between high-level science and actionable governance. It ensures that when urban planners in developing nations or mayors in major metropolises approach climate adaptation, they do so with the weight of global scientific consensus behind them.
Implications for the Seventh Assessment Cycle (AR7)
The Special Report on Climate Change and Cities is the vanguard of the Seventh Assessment Cycle (AR7). Following the successful completion of the Sixth Assessment Report (AR6) in 2023—which provided essential data for the Global Stocktake at COP28—the Seventh Cycle aims to refine the precision of our climate models and adaptation strategies.
The AR7 landscape is expansive. In addition to this special report, the IPCC is concurrently working on:
- Working Group I: The Physical Science Basis of climate change.
- Working Group II: Impacts, Adaptation, and Vulnerability.
- Working Group III: Mitigation of Climate Change.
- Methodology Reports: Including the 2027 Report on Carbon Dioxide Removal Technologies and the 2027 Inventory for Short-lived Climate Forcers.
The focus on cities reflects a shift in the IPCC’s strategic priorities. As the world moves toward 2030, the ability of urban centers to implement mitigation—such as green transport, energy-efficient building codes, and resilient water management—will determine whether global climate goals are met.
How Experts Can Participate
The IPCC process relies on the volunteerism of the world’s leading scientists, urban planners, and policy analysts. The current call for Expert Reviewers is a request for the global intellectual community to lend its time and expertise to a document that will be cited for decades to come.
Interested professionals are encouraged to visit the official IPCC registration portal before the June 26, 2026, deadline. By participating, experts contribute to a document that aims to protect the billions of people living in urban areas, ensuring that the policies of the future are built upon the most robust science available today.
About the IPCC: The Guardian of Climate Science
The Intergovernmental Panel on Climate Change (IPCC) serves as the United Nations’ premier body for assessing the science of climate change. Established in 1988 by the World Meteorological Organization (WMO) and the United Nations Environment Programme (UNEP), the IPCC has grown into an institution of 195 member states.
The IPCC does not conduct original research; rather, its thousands of contributors assess the thousands of peer-reviewed scientific papers published annually. This synthesis provides political leaders with the objective, evidence-based assessments necessary to negotiate international climate agreements. Through its three Working Groups and its Task Force on National Greenhouse Gas Inventories, the IPCC creates the scientific framework that underpins virtually all international climate policy.
For further inquiries regarding the review process, potential participants or media representatives are encouraged to contact the IPCC Working Group II Technical Support Unit at [email protected] or reach out to the IPCC Press Office in Geneva.
As the world watches the unfolding impacts of climate change on our cities, the upcoming report stands as a vital opportunity to turn the tide. The call for experts is more than an administrative step; it is an invitation to define the future of human habitation in a warming world.
Rifan Muazin
Layla Zulfa
