September 6, 2021, by Brigitte Nerlich

IPCC reports, climate change and language work

This blog post is not about climate change communication. It is about what I call the ‘language work’ carried out by scientists when writing the various IPCC reports.


On 9 August 2021 the first part of the Sixth Assessment Report of the Intergovernmental Panel on Climate Change, namely the Contribution of Working Group 1 on The Physical Science Basis, was made public. It said yet again, but more forcefully, with even more fine-grained scientific evidence and, interestingly, it seems, more plainly and clearly, that climate change was widespread, rapid and intensifying.

When this latest IPCC report, AR6 for short, was published, I was still in the middle of dealing with the aftermath of the massive floods in Germany that hit my home town on 14 July. This week, i.e. at the beginning of September, my father got his heating back and, finally, also his telephone, TV and internet. It took a long time. And he was one of the lucky ones. Anyway, I am now getting a bit more headspace to think about things other than pipes and cables.

A few days ago, a Twitter friend, @gudiule, whom I came to know during the flooding emergency, sent me a radio programme by France Culture, called “Le climat au rapport” which was about the IPCC report or in French GIEC report (Le Groupe d’experts intergouvernemental sur l’évolution du climat).

During the broadcast, one of the thousands of contributors to the IPCC report talked about the language wrangling they had to accomplish. This impressed him, I think, much more than the data wrangling he was used to. That reminded me of a part of the English press conference I HAD managed to watch a few weeks ago, where a French journalist noted that the AR6 was much more understandable than previous reports and asked why that was. All this made me think about what I know and what I don’t know about the IPCC and language.

What I know from previous years of observing the reporting of the IPCC reports is that the experts involved try very hard to talk about uncertainty in such a way that people understand what’s going on. I also know that the final summary to policy makers is a work of linguistic diplomacy of the highest order, as each sentence has to be accepted by representatives of all nations. What I hadn’t appreciated enough perhaps was the hard linguistic labour that goes into all this.

I’ll first summarise what caught my eye on language and climate change during the current AR6 reporting and then come back to some older issues which may, however, still be of interest, pertaining to AR5 and language. I’ll close with some reflections on a potential role that the language sciences could play in the drafting of IPCC reports. If you want you can skip part 2 and go straight to the conclusion…

Part 1 – Language and AR6

Plain language

When AR6 was made public, viewers all over the world could tune into a press conference. I watched one part of it called climate change 2021. During a question and answer session scientists, speaking English with French or Finnish or German etc. accents, tried to make very clear what the IPCC does and how does it, and they also highlighted the fact over and over again that they are not there to prescribe policies. But that is a topic that would need a separate blog.

What interested me was how proud Valérie Masson-Delmotte, a French climate scientist and co-chair of Working Group 1, was about the way that art, design and language have been used to make the report more accessible.

1 hour 14 minutes into the press conference Marie-Noëlle Bertrand, a journalist for L’Humanité, noted that the new report seemed to be easier to understand and was better illustrated than the older ones, and asked: Is this for people to understand it better or for politicians to finally understand?

Valérie replied by saying that in this report the scientists had taken every care to present the outcome of advances of complex climate science in the clearest possible way. She highlighted  that they had used plain language in answers to questions asked in the report and in the summary for policy makers. She pointed out that they also wanted to make sure that figures could be intuitively understood. Overall, she hoped that the report would help enhance climate literacy worldwide and would be used in teaching all over the world so that students can learn about the latest best available knowledge. She also hoped it would help decision makers and engineers involved in all sectors to build on this latest science so that they can use it and develop responses as quickly as possible.

The speaker following Valérie, Petteri Taalas, the Secretary-General of the World Meteorological Organization, stressed the fact that decisions makers are taking climate change more seriously now, something that was partly due to science communication that has happened since 1988 and partly to impacts becoming more visible now.

Language work

Now to the French episode on the IPCC. This was, interestingly, part of a programme called ‘La méthode scientifique’ hosted by Antoine Beauchamp and Nicolas Martin. For this episode they interviewed two lead authors of the IPCC report, Sophie Szopa, a specialist in tropospheric chemistry working at the Laboratoire des Sciences du Climat et de l’Environment, and Robert Vautard, a meteorologist and director of the Institute Pierre Simon Laplace.

18 minutes and 16 seconds into the episode, Robert Vautard talked about his surprise at finding out how difficult it was to write a sentence for the IPCC report, an experience that was totally different to writing a sentence for a normal scientific article. First, he said, there is the feeling of immense responsibility for humanity as a whole which means one has to pay extreme attention to what one says. Second, and most importantly, he stressed that you don’t just write one word after another; you realise that each word may be interpreted differently by all the co-authors of the report. However, it is essential that all the authors coming from different countries and speaking different languages understand the same thing by that word. This means that constructing a sentence while finding the right words is an extremely complex task.

Vautard pointed out that each sentence is written and rewritten, read and reread, turned around this way and that…and sometimes, he said, one spends hours if not days on the definition of terms so that they can be understood in a universal fashion. For example, he points out that they discussed endlessly a phenomenon that may lead to physical impacts and trying to find a word or phrase for it that has no negative or positive connotations. This is, he said, because it is the role of IPCC to provide the balance sheet of knowledge (‘bilan des connaissances’) about the physical climate system without, however, implying that something will be dangerous, beneficial and so on – which could influence policy.

I have, of course, only roughly transcribed and paraphrased a fraction of this interesting radio programme. I just wanted to provide a glimpse of the profound language work that goes on in the background when scientists write the IPCC reports, over and above ‘just’ summarising the science.

When quickly checking the press reporting following the press conference, I found that the word ‘clear’ was used a lot (I haven’t quantified that!); so, it seems the authors of this report achieved their aims, after a lot of hard work. What impact that might have on actions by decision makers is another matter, in a climate where merchants of doubt are still active and populism is on the rise.

Part 2 – Language and AR5

Now I want to go back to some things we had already learned about language when a previous IPCC report was published, namely AR5 in 2014.

Uncertainty language

Uncertainty is a difficult word and has provoked a lot of discussion in the context of climate change. Those who report on the state of science concerning climate change have wrangled with such concepts for a long time.

Since 2007 all IPCC reports have adopted a ‘calibrated language’ approach to communicating scientific uncertainty in order to, in a sense, “reduce doubt about uncertainty” (Moss, 2011). This calibrated language is based on verbally paraphrasing numerical (probabilistic) degrees of ‘certainty’, ‘confidence’ and ‘likelihood’ (see image).

In our work on climate change communication Luke Collins and I wondered whether this carefully calibrated language trickles through to the media, as it is through the media that most people and policy makers gain knowledge about the latest research on climate change.

The English-speaking news media we surveyed both quantitatively and qualitatively showed some awareness of the IPCC’s calibrated language but preferred to use a type of framing of uncertainty through, sometimes flawed, analogies, referring to the discourse of medicine, of insurance and to other well-established scientific claims.

There was, we noted, some danger in using metaphorical language instead of calibrated language, as the appropriation of a more familiar concept introduces dimensions that can be incongruous with the original claim, such as the compensatory dimension of the insurance analogy.

Another word that is causing a lot of trouble in climate change speak, over and above ‘certainty’ or ‘uncertainty’ is that of consensus. There is the scientific consensus about the main issues related to climate change, but there is also another type of consensus.

Language and consensus

The process of approving sentences in the summary report for policy makers, the final stage of the language wrangling that goes into writing IPCC reports, has been described by The Economist in the following terms in an article entitled: “Inside the sausage factory; Climate change”:

“The process was described by one participant as ‘exceptionally frustrating’ and by another ‘one of the most extraordinary experiences of my academic life’. It works as follows. The authors write a draft summary. Each sentence of the draft is projected onto a big screen in a giant hall. Officials then propose changes to the text; authors decide whether the changes are justified according to the full thousand-page report. Eventually a consensus is supposed to be reached, the sentence is approved or rejected, the chairman bangs a gavel and moves on to the next sentence.”

This is part of the IPCC consensus process, which, of course, has nothing to do with the overwhelming scientific consensus that has been reached over decades about the nature and impacts of climate change and which is summarised in the IPCC reports. Unlike in this process, scientific knowledge is, generally speaking, not a product of consensus as intentional or planned action.


Like Robert Vautard, I was surprised to find just how much language work or language wrangling goes into the IPCC reports. Finding a word, a phrase or a sentence that is understood across languages and that doesn’t have any connotations that might guide policy and so on is a tall order. But I was also surprised to find that authors of the current report praised the contributions made by designers and artists but didn’t mention contributions by language experts, such as linguists, rhetoricians, translators and so on.

I know there have been calls to involve more social scientists and communication experts in the writing of the IPCC reports. However, problems flagged up by scientists regarding the language work they do flag up issues that are quite different to those discussed normally in climate change communication circles and might need different skill sets to be properly tackled.

Image by Gerd Altmann from Pixabay



Posted in Climate ChangeClimate PoliticsLanguageScience Communication