The Intergovernmental Panel on Climate Change (IPCC) uses a formal, named-role authorship system for its Assessment Reports and Special Reports — Coordinating Lead Author (CLA), Lead Author (LA), Contributing Author (CA), and Review Editor (RE), plus a non-authoring Chapter Scientist support role. This system looks superficially similar to journal-article authorship (it uses the phrase “lead author,” it produces a named byline per chapter) but it is built on a genuinely different foundation: government and observer-organization nomination, Bureau selection, and collective chapter responsibility, rather than the contribution-based criteria that govern a journal manuscript under ICMJE or CRediT. Confusing the two conventions is an easy mistake for anyone moving between climate-science policy documents and standard academic publishing — this guide explains each IPCC role, how people are selected into them, and exactly how the system differs from journal-article authorship.
Why This Distinction Matters
CASRAI’s Lead Author dictionary entry already flags that “lead author” has two unrelated senses: an informal synonym for first author in journal-article usage, and a formal, appointed role in team-authored assessment reports such as IPCC’s. This guide is the deep-dive on that second sense. It does not replace or duplicate the dictionary entry — it exists because the IPCC role hierarchy has four additional named positions (CLA, CA, RE, and the non-author Chapter Scientist support role) and a distinct nomination-and-selection process that a short dictionary definition cannot cover in full, and because researchers, institutional press offices, and research administrators increasingly need to correctly describe an IPCC contribution on a CV, biosketch, or grant report without misrepresenting it as ordinary journal authorship.
The IPCC Author Hierarchy: Four Roles, One Non-Author Support Role
Every IPCC Assessment Report chapter is produced by an author team with a defined internal structure. Per IPCC’s own procedural documentation, the roles are:
- Coordinating Lead Author (CLA) — coordinates a chapter as a whole. CLAs are responsible for drafting the chapter and revising it in response to the two mandatory IPCC review rounds (an Expert Review, followed by a joint Government and Expert Review), and for reconciling different sections of the chapter into a coherent whole. Most chapters have two CLAs.
- Lead Author (LA) — responsible for producing an assigned section within the chapter, drawing on the best available scientific, technical, and socio-economic literature, and for helping respond to review comments on that section.
- Contributing Author (CA) — provides specific expertise, text, graphics, or analysis on a defined sub-topic at the request of the CLAs/LAs, without carrying the same chapter-wide drafting and revision responsibility. A chapter’s Contributing Authors are listed separately from its CLAs and LAs.
- Review Editor (RE) — not part of the writing team. Review Editors oversee how the author team handles expert and government review comments, help ensure genuine scientific disagreement is fairly reflected rather than smoothed over, and advise on how to resolve contentious issues. Their time commitment is lower than a Lead Author’s but includes attendance at Lead Author meetings.
- Chapter Scientist — a support role, not an authorship category. Chapter Scientists (often early-career researchers) assist the author team with reference management, cross-checking findings between different parts of the report, and additional fact-checking. They are not listed as chapter authors.
All CLAs, LAs, and CAs for a chapter share collective responsibility for that chapter’s content once it is finalized — there is no equivalent of a single accountable “corresponding author” for the whole document, and no ranked byline order carrying the same meaning as journal-article author position.
How IPCC Authors Are Selected
This is the step with the clearest structural difference from journal authorship. IPCC author selection runs on a fixed cycle tied to each Assessment Report:
- Nomination. After a report’s outline is agreed, IPCC issues a formal call for nominations. Nominations for CLA, LA, and RE positions are submitted by IPCC Focal Points (national government contacts), Observer Organizations, and/or IPCC Bureau members — not by individual researchers applying directly on their own initiative, and not by an editor inviting a specific known expert the way a journal sometimes does.
- Selection. The relevant Working Group Bureau (Working Group I covers physical science, II covers impacts/adaptation/vulnerability, III covers mitigation) selects CLAs, LAs, and REs for each chapter from the nominee pool, aiming for a balance of scientific expertise, geographic representation, gender balance, and a mix of experienced and early-career authors.
- Team assembly. Once CLAs and LAs are in place, they in turn identify and invite Contributing Authors for specific expertise gaps as chapter drafting proceeds — this step is closer to how a journal-article research team might add a specialist collaborator, but it happens inside an already-nominated, Bureau-approved structure.
The IPCC’s Seventh Assessment Report (AR7) cycle followed this same pattern: a call for CLA, LA, and RE nominations went out through national Focal Points and observer organizations, closed, and Working Group Bureaus announced selected authors.
IPCC Roles vs. Journal-Article Authorship: Key Differences
| Dimension | IPCC Assessment Report | Journal-article authorship (ICMJE / CRediT) |
|---|---|---|
| How someone becomes an author | Nominated by a government Focal Point, Observer Organization, or Bureau member; selected by the Working Group Bureau | Self-determined by the research team based on meeting ICMJE’s four authorship criteria (substantial contribution, drafting/revision, final approval, accountability) |
| What defines the role | A fixed position in a nomination-based hierarchy (CLA, LA, CA, RE) tied to a chapter, not to a specific documented contribution type | Either byline position (contribution-ranked, discipline-dependent) or a specific CRediT contributor role such as Conceptualization or Formal Analysis |
| Is there a “first author”? | No — CLAs, LAs, and CAs are each listed as groups, typically alphabetically within group, not ranked by contribution | Often yes, in contribution-ranked fields — first author conventionally signals the largest share of the work |
| Accountability model | Collective chapter responsibility shared across the CLA/LA/CA team | Individual accountability per ICMJE criterion four, though corresponding authors typically handle correspondence |
| Review process the authors respond to | Two IPCC-mandated review rounds: Expert Review, then a joint Government and Expert Review, both applied at the whole-report/chapter level | Journal peer review, typically 2–3 reviewers per manuscript, applied before publication of that specific article |
| Oversight of the review process | A dedicated Review Editor role, independent of the writing team | The journal’s editor(s), not a role held by any author |
| Formal credit taxonomy used | None — role titles (CLA/LA/CA/RE) are the credit system; there is no equivalent of a CRediT-style itemized contribution statement | Increasingly, a CRediT contribution statement alongside the byline, required or recommended by many journals and funders |
| Term of appointment | Tied to one Assessment Report cycle (roughly 6–7 years) | Tied to a single manuscript/publication |
Why There’s No “First Author” on an IPCC Chapter
Journal-article authorship in many fields uses position in the byline as an informal proxy for contribution size — the person listed first is conventionally understood to have done the largest share of the practical work, and the last/senior position often signals the lab or project lead. CASRAI’s First Author entry covers that convention in depth. IPCC chapters do not use this convention at all. CLAs, LAs, and CAs are each printed as a group on the chapter’s title page, and within each group names commonly appear alphabetically rather than in a contribution-ranked order. There is no single individual whose name functions the way a corresponding or first author’s does on a journal article — responsibility for the chapter’s content is explicitly collective across the CLA/LA/CA team, which is a deliberate design choice reflecting that an Assessment Report chapter synthesizes existing published literature rather than reporting a single new study a specific individual “owns.”
Documenting an IPCC Role on a CV, Biosketch, or Institutional Report
Because the IPCC role system doesn’t map onto CRediT or ICMJE categories, researchers documenting this work for career or funding purposes should name the specific role and report cycle explicitly — for example, “Lead Author, IPCC Sixth Assessment Report, Working Group I, Chapter 4” — rather than describing it generically as “authorship” or, worse, as “lead author” in a way a reader might mistake for first authorship on a journal article. Institutions compiling researcher profiles or REF/RAE-style impact case studies should treat an IPCC CLA/LA appointment as a distinct credential category, comparable in kind to an editorial board membership or a major review-panel role, rather than folding it into standard publication-authorship counts.
Frequently Asked Questions
Is an IPCC Lead Author the same as a journal article’s lead/first author?
No. They share a label but not a definition. A journal’s lead/first author is typically the contributor judged to have done the largest share of the practical work, determined informally by the research team. An IPCC Lead Author is a formally nominated and Bureau-selected position responsible for a section of an Assessment Report chapter, unrelated to contribution ranking.
Who can become an IPCC Coordinating Lead Author or Lead Author?
Nomination comes through a government’s IPCC Focal Point, an accredited Observer Organization, or an IPCC Bureau member — not through direct application by an individual researcher. The relevant Working Group Bureau then selects from the nominee pool for each chapter, considering expertise, geographic and gender balance, and a mix of career stages.
What does a Contributing Author do differently from a Lead Author?
A Contributing Author provides specific expertise, text, data, or graphics on a defined sub-topic at the request of the chapter’s CLAs/LAs, without carrying the chapter-wide drafting and revision responsibility that CLAs and LAs hold. Contributing Authors are listed separately from the CLA/LA group on the chapter.
Does a Review Editor write any of the report?
No. The Review Editor role is oversight, not drafting. Review Editors ensure the author team has genuinely addressed expert and government review comments and that legitimate scientific disagreement is fairly represented, but they are not part of the writing team and their time commitment is lower than a Lead Author’s.
Is a Chapter Scientist listed as an author?
No. Chapter Scientist is a technical and logistical support role — reference management, cross-checking findings across the report, additional fact-checking — not an authorship category, and Chapter Scientists are not listed among a chapter’s CLAs, LAs, or CAs.
Does IPCC authorship use CRediT or follow ICMJE criteria?
No. IPCC’s CLA/LA/CA/RE structure predates and operates independently of both. There is no CRediT-style itemized contribution statement on an IPCC chapter, and ICMJE’s four-criteria authorship test, built for a single research article with an identifiable set of contributors, does not govern a nomination-based, government-mediated nomination and Bureau-selection process.
