An Insider's Perspective on the IPCC Process from Dr. Hans-Otto Pörtner

Written by Natalya on .

Dr. Pörtner served as one of the two coordinating lead authors for the Ocean Systems chapter of the IPCC AR5 WG2 Report that was finalized and officially released in 2014. He is a professor in Integrative Ecophysiology at the Alfred-Wegener Institute in Germany and attended COP 20 to present during a special event on the AR5 Synthesis Report. In Lima, I had the opportunity to sit down with Dr. Pörtner and hear about his experiences serving as a coordinating lead author for the Ocean Systems chapter, and ask about his perspective on how the IPCC reports are used by COP negotiators to arrive at decisions about national climate change targets. 

First, a brief overview – the IPCC stands for the Intergovernmental Panel on Climate Change and was first established in 1988. Every few years, the IPCC puts out an assessment report that represents the international scientific consensus on climate change. Now, we are on the 5th full assessment report, called AR5. Each assessment report consists of 3 working groups that are released sequentially. Working Group 1 (WG1) is on the Physical Science Basis of Climate Change (and the final was released last year in 2013). Working Group 2 (WG2) is on the Impacts, Adaptations, and Vulnerabilities from Climate Change and was released in 2014. And Working Group 3 (WG3) is on the Mitigation of Climate Change.

The creation of an assessment report is a huge international effort. To put it in perspective, 308 authors from 70 countries were involved in writing the WG2 report that Dr. Pörtner contributed to, and the final version of the WG2 report is 1,820 pages long. Follow along with this infographic as you read about the IPCC process. 

Dr. Pörtner first became involved in the IPCC process in the late 1990s when he was asked to contribute to a special report on Carbon Dioxide Capture and Storage for the 4th assessment report (AR4) because his lab was one of the few at that time studying how extra CO2 in water physiologically affected marine organisms. In 2009, he was then asked to serve as a coordinating lead author for a brand new chapter on Ocean Systems for the 5th IPCC Assessment Report. It’s important to note that the AR5 WG2 report is the first one that has a whole sectoral chapter devoted to Ocean Systems, a second one focuses on Ocean Regions. Dr. Pörtner explained that each WG report chapter is produced by 2 coordinating lead authors who are directly responsible for the chapter, multiple lead authors who take over specific sections of the text, and then additional contributing authors who are contacted based on their expertise to fill in identified gaps in information. A great deal of scientific expertise and time go into the crafting of each of these chapters. To put it in perspective, the first scoping meeting for the AR5 report took place in 2009, so the process of selecting authors, writing and finalizing the AR5 WG2 report took about 5 years.

Through our conversation, Dr. Pörtner shed light on some of the different products that come out of the assessment process. For example, each working group produces the final report, but also two important distillation products: the technical summary and the summary for policy makers (SPM). I was interested in how the uses of these reports differ and how this affects how scientists contribute to them. Dr. Pörtner said that the report itself (chapter by chapter) is a good broad overview of the current body of knowledge on the topic, and the appropriate audience for this is the scientific community itself. For example, as a new PhD student interested in climate change impacts in the ocean, the Ocean Systems Chapter of the AR5 WG2 report would be a great place to start to get an overview of the known ocean impacts from climate change.

However, if you’re a policymaker, you really don’t have time to read through the dense IPCC report chapters, so that’s where the important distillation products come in. These distillation products are the technical summary, the summary for policymakers (SPM), and the synthesis report. The technical summary is an important distillation of the main scientific findings of each of the working group reports and the technical summary for the AR5 WG2 Report is only 60 pages compared to the 1,820 pages of the complete WG2 Report. Here, the main scientific findings, as determined by the scientists contributing to the main report are summarized. The summary for policymakers builds on the technical summary but differs, as Dr. Pörtner explained, in that this is viewed as a joint product of the IPCC authors with their governments. For a week, government representatives and IPCC authors go over the main findings from the WG report and, through a consensus process, arrive at a final document that highlights the main scientific findings of the WG report that are most valuable to policymakers. For comparison, the final summary for policymakers (SPM) of the AR5 WG2 Report was 32 pages long, and is probably the WG product most used and referred to by negotiators. For this reason what makes it into the SPM (and what doesn’t) is extremely important.


The SPMs for each WG are also very important because they are used, together with the full report, to assemble the Synthesis Report. Unlike the technical summary and the SPM, which are produced for each of the 3 WG reports, only one Synthesis Report is produced for each IPCC Assessment Report. So, for the entire (5,000+ page) IPCC 5th Assessment Report, there is only one 139 page Synthesis Report, which brings together the main scientific findings from each of the 3 WG reports into one document. Dr. Pörtner played an important role in the writing of the Synthesis Report because, of the 51 authors making up the core writing team for the Synthesis Report, he was the only one representing ocean impacts. In my opinion, the Synthesis Report is likely the most politically important document from the IPCC Assessment process, and Dr. Pörtner was attending COP 20 to participate in a structured expert dialog for negotiators about the new scientific conclusions presented in this Synthesis Report.

Despite the tremendous amount of work Dr. Pörtner’s contributions to the IPCC process have required, he reports that he has had a very positive experience and would consider contributing in similar ways in the future. He also said that his home institution, the Alfred-Wegener Institute, was very supportive of the effort required to serve as coordinating lead author for the Ocean Systems Chapter.

Dr. Pörtner left me with a few points that I would like to finish this blog entry with. First, he stressed the importance of open-mindedness in the IPCC process, especially when dealing with the concerns and the thinking of others. This is especially important for the production of the technical summary, SPM, and synthesis report, which require authors to agree amongst themselves (through convincing and compromising) on what’s important and what should be included. For example, Dr. Pörtner was happy that a figure on fisheries and food security was included in the SPM of the final AR5 Synthesis Report, but would also have liked to see a figure on ocean acidification in the SPM. Such figures are to be found, however, in the underlying main Synthesis Report.

Dr. Pörtner also pointed out the importance of structured expert dialogues and the role of UNFCCC and government experts in actually communicating the results from the distillation products to lead negotiators who are working on determining allowable climate targets. These experts are the connection between the IPCC products and the use of these products by the negotiators. From his experiences, Dr. Pörtner emphasized that science is most useful for policymakers when: 1) observed and projected impacts are specific and attributed to ongoing climate change, 2) time and spatial scales for projected impacts are clarified (short-term or long-term impact and regional or global impact, respectively), and 3) projected full-ecosystem level changes are described in the context of different Representative Concentration Pathway (RCP) scenarios.

Resolution of spatial and temporal scales and predicting whole ecosystem changes are some of the trickiest questions to answer for the scientific community, but it’s great to hear that scientists are identifying the needs of policymakers and are actively working to communicate the immense knowledge of the scientific community in a manner that is most useful for the political process in establishing global limits for climate change.

While lengthy, I hope this blog post has provided some insight into the multiple IPCC products, and the ways in which they’re produced and used. I also hope this has left you with an appreciation for the immense amount of work these products represent. A lot of the intricacies of this process were unclear to me as a PhD student prior to sitting down with Dr. Pörtner, so I would like to thank him for his time and willingness to share his experiences participating in the IPCC process with me. 

For more information, visit the IPCC AR5 Website

If you’d like to learn more about how the IPCC contributing scientists interact with Party representatives, you can check out summary reports that provide insight on the structured expert dialogues and are publicly available here with notes from the co-facilitators. 


Tags: IPCC

Contact Information

Ocean Scientists for Informed Policy
Scripps Institution of Oceanography
University of California, San Diego
9500 Gilman Drive
La Jolla, CA 92083-0202