Author: Mounia Mostefaoui, PhD Student at Sorbonne University
Topic: Climate Change, IPCC working groups, IPCC Reports, IPCC Sixth Assessment Report (AR6), Synthesis Reports for Decision-Makers, IPCC Special Reports
In this paper, we would like to present key insights on the diverse types of reports produced by the Intergovernmental Panel on Climate Change (IPCC). We will first deliver a brief historical overview of the origins of the creation of the IPCC. We will then summarize its main missions. Finally, we will provide an overview of the production process of the IPCC Reports and their accessibility.
1. Some history regarding the creation of IPCC
In 1979, the American scientist Jule Charney published a 22-page report to the National Academy of Science in the US on global warming resulting from anthropogenic greenhouse gases emissions and its associated risks.  This impactful document led to a movement of global consciousness awakening from the civil society and from policymakers regarding this issue. In 1987, the teams of Jean Jouzel and Claude Lorius published the analyses of ice cores that were drilled at the Vostok station in Antarctica.  The pioneering work of Charney, Jouzel, Lorius and some other scientists led the American President Ronald Reagan and the British Prime Minister Margaret Thatcher to decide notably during the 1988 G7 that a United Nation body for mapping the state of knowledge regarding the science of climate change should be created. Therefore, as a result of this political decision based on a scientific diagnostic, the Intergovernmental Panel on Climate Change (IPCC) was implemented in 1988 within the United Nations Environment Program and the World Meteorological Organization.
2. The IPCC main mission: an interdisciplinary mapping of the current state of the art regarding the scientific knowledge on climate change
The missions of the IPCC are to regularly deliver updated insights regarding the state of the art of the science of climate change as well as its associated risk, and to make proposals regarding both adaptation and mitigation solutions. The IPCC is an international structure composed of 195 member states. The different IPCC reports deliver a detailed bibliographical synthesis of the existing scientific knowledge including both peer-reviewed articles on the one hand, and papers coming from the “grey literature” on the other hand. They are mainly destinated to country leaders as a non-prescriptive support for public policy decision-making and as a support for the implementation of national laws regarding climate change. The IPCC doesn’t conduct any research on its own and delivers only a work of synthesis regarding the global scientific production.
One key feature of the IPCC is its interdisciplinary DNA, both in terms of members and regarding the topics involved in the assessment, from the physics of climate change, to economics, sociology, public policy, national and international law, etc. More specifically, the IPCC missions are subdivided under the attributions of three Working Groups and a Task Force on Greenhouse Gases Emissions. The scientists involved in the IPCC reports redaction involve around ten permanent staff members of the IPCC’s Secretariat. Those permanent members are related to the following three Working Groups:
- The Working Group I (WGI) has a focus on the physical science of climate change.
- The Working Group II (WGII) studies the impacts, adaptation and vulnerability aspects of the question.
- The Working Group III (WGIII) focuses on the mitigation of climate change.
Finally, the Task Force on National Greenhouse Gas Inventories works on methods and processes for measuring greenhouse gases emissions and Carbon sinks.
The IPCC reports result from the different contributions from those three Working Groups plus the Task Force and represent a major source of information for the international negotiations related to climate change that take place every year at the occasion of the annual Conference of the Parties.
3. Generalities about the production IPCC Reports
The IPCC reports are included in “assessment cycles” which are referred to with a number and each assessment period lasts five years. It is also important to note that all the types of IPCC reports listed below are freely available to the general public directly on the IPCC website. 
3.1. The Assessment Reports
Within one assessment cycle, the IPCC Assessment Reports are produced following different steps including first and second order drafts, reviewed by hundreds of independent international expert scientists, on a voluntary basis. The expert reviewers are selected after an application process from the IPCC based on their experience / international background and their publications. The chosen expert reviewers are hired based on the diversity of their background to make sure that the largest possible variety of insights is taken into account for a rich perspective on the various topics. Each comment by review editors is taken into account, a process which insures the transparency and the reliability of the reports. For each IPCC Report, an order of magnitude of thousands of articles coming from both peer-reviewed papers and from the grey literature are assessed. This almost exhaustive review ensures that the largest possible diversity of scientific production is taken into account.
As for the more recent assessment cycle for instance, the decision to deliver the Sixth Assessment Report - also referred to as AR6 - was taken during a meeting in February 2015 named the IPCC 41st Session, in the city of Genova.
3.2. Special Reports
The IPCC can also produce Special Reports for example at the request of a government asking for more scientific information to assess a given issue. In 2019, the IPCC delivered three Special Reports:
- A Special Report on Global Warming of 1.5°C.
- A Special Report on the Ocean and Cryosphere in a Changing Climate.
- A Special Report on Climate Change and Land.
The Special Reports provide an interdisciplinary evaluation of those topics and involve more than one Working Group. The Special Reports are less dense in terms of volume and content than the regular IPCC Assessment Reports.
3.3. The Synthesis Reports
The Synthesis Reports are focused on diverse important issues related to policy. They include the inputs coming from the Assessment Report and the inputs from the Special Reports produced during a given 5-year assessment period. The Synthesis Reports contain several chapters and may also include a Technical Summary. As for the Synthesis Report within the Sixth Assessment Report, its delivery date is forecasted for the second trimester of 2022. It will gather all the contributions coming from the three Working Groups which are planned to be delivered in 2021.
3.4. The Summary for Policymakers (SPM)
Within each assessment period, around fifty scientists are chosen and join the efforts of the Working Groups to deliver a first order draft of another type of IPCC report called the Summary for Policymakers (SPM) mainly intended for government leaders. This type of Report has a separate elaboration process and is based on a consensus for the framing.
First, each Working Group synthesizes its inputs coming from the Assessment Report in a first draft of the SPM. This proposed Report has then to be approved line by line by governments representatives through a dedicated discussion process for agreeing on a final version of the text. The sentences are displayed on a screen visible by all the participants, and during the rewriting process, paragraphs are added or removed as necessary. The new draft is reviewed during a plenary session including both national government delegates and observers. The plenary sessions are placed under the complete supervision of the different Working Group Chairs to make sure that the scientific message is faithfully translated into a framing designated to the policymaking area. This review process aims at clarifying the message of the SPMs while preserving the core of the scientific inputs. As for the policymakers’ representation, each delegation sends about six representatives including their local experts that may belong to the IPCC, as well as other public officials or experts of diplomacy/negotiations.
In case of a high disagreement, a small group with the main actors involved is created by a Working Group Chair in order to accelerate the process and to negotiate a mutually satisfactory framing.
3.5. The Methodology Reports
Another kind of documents produced by the IPCC are the Methodology Reports. Their purpose is to deliver operational advice regarding the elaboration of national greenhouse gas inventories. They contain an “Overview Chapter” with the inputs of the Summary for Policymakers.
All the Reports described above can also contain a section named “Frequently Asked, Questions” as well as a section called “Supplementary Material”.
3.6. An example of IPCC report’s impact
The direct impacts of the gigantic work done by the IPCC are not necessarily easy to measure. However, in some cases, their consequences in terms of political decision are clearly identifiable.
The most impactful reports regarding public and political awareness on climate change are certainly the summaries for policymakers with synthetized information regarding the critical findings from the main assessment or special reports.
As an example, the European Green New Deal announced by Ursula von der Leyen during COP25 in 2020 is directly quoting the scientific findings of the IPCC 1.5°C report to justify its stated targets, including the proposal to set a climate law to achieve climate neutrality by 2050.  More globally, the international texts of the United Nations Framework Convention on Climate Change (UNFCCC) are based on the results presented in the IPCC reports.
In this paper, we presented a brief historical perspective regarding the creation of the IPCC and provided a global picture of its main missions, consisting in the cartography of the current state of the art regarding the scientific knowledge on climate change and featured by a strong interdisciplinary dimension. This responsibility is placed under the supervision of three Working Groups and a Task Force on Greenhouse Gases Emissions. Finally, we described the general process for the production of the IPCC reports that are free and publicly available, with a highlight on the IPCC Sixth Assessment Report (AR6) which is forecasted to be publicly available in 2022. An example of international political impact of the IPCC reports with the case of the Green New Deal was also underlined in this paper. The story is to be closely followed in the coming months with the inputs from AR6!