Guest post: What 13,500 citations reveal about the IPCC’s climate science report

In August 2021, the Intergovernmental Panel on Climate Transform (IPCC) published their extended-anticipated report on the “physical science basis” for climate modify. 

The report concluded that climate modify is “unequivocally” brought on by humans and currently affecting just about every area on our planet. These findings have been reported about the globe, drawing international interest.

The mammoth two,500-web page document brings collectively an huge volume of peer-reviewed literature to deliver the most up-to-date summary of climate science however published. Each statement in the report is backed up by authoritative sources.

Altogether, the report boasts a staggering 13,500 citations.

Our evaluation explores which citations have been incorporated in the report and reveals a surprisingly broad and diverse variety of subjects.

On the other hand, it also shows that citations in the report are heavily dominated by the international north and frequently sit behind a paywall.

We discovered that 99.95% of the cited references have been written in English and 3-quarters of all literature cited in the report featured at least a single author primarily based in either the US or the UK.

When and exactly where?

The IPCC’s report on climate science – identified as the Functioning Group I (WG1) report – is the initially section of the 3-portion sixth assessment report (AR6). Hundreds of scientists spent years assessing the current literature on climate modify to make this report, which will type the cornerstone of climate science for the years ahead.

The report was followed by two other instalments on the impacts, adaptation and vulnerabilities of climate modify and the mitigation of climate modify, released in February and March 2022, respectively. The AR6 will conclude with a synthesis report, released subsequent week.

The AR6 WG1 report is an update from the fifth assessment cycle (AR5) WG1 report, which was published in 2013. Authors of the new report have been encouraged to concentrate on supplying an update because the final cycle, explaining the advances in climate science, how the self-confidence of findings had changed or strengthened and what new subjects had emerged because AR5.

We discovered that 98.five% of citations in the AR6 WG1 report have been published because the year 2000 and 85% of have been published right after the release of the AR5 in 2013. The chart under shows how numerous citations have been published just about every year more than 2000-21.

Year of publication year for all IPCC AR6 WG1 report references published in between 2000 and 2021. Credit: Félix Chavelli.

We discovered that 290 (two%) of references are from January 2021, reflecting a push from the scientific neighborhood to get papers accepted for publication prior to the report’s literature reduce-off date on 31 January 2021.

The oldest citation – “An historical account of the trade winds, and monsoons, observable in the seas in between and close to the Tropics, with an try to assign the physical trigger of the mentioned winds” – was published by English astronomer and mathematician Edmond Halley in 1686.

We also analysed exactly where the authors of each and every paper have been primarily based at the time of its publication. In total, the 13,500 citations have about 39,000 exclusive authors. On the other hand, numerous authors co-authored extra than a single of the cited papers, and this quantity jumps up to virtually 130,000 names when these duplicates are counted.

The dominance of the international north amongst the citation authorship is stark. Although 185 nations are represented across the citations, we estimate that extra than 80% of authors are primarily based in the international north. The map under illustrates this with a subset of papers published in between 2011 and 2020. The quantity in each and every bubble shows the quantity of authors primarily based in that nation.

Country location of all the co-authors from the papers cited in the WG1 report that were published between 2011 and 2020.Nation place of all the co-authors from the papers cited in the WG1 report that have been published in between 2011 and 2020. Map produced employing SciVal. Credit: Félix Chavelli

3-quarters of all literature cited in the report characteristics at least a single author primarily based in either the US or the UK. Additional than six,000 of the references include things like at least a single author primarily based in the US. 

In addition to the US and UK, Germany, France, China, Australia, Switzerland, Canada, Japan and the Netherlands are also represented in extra than 1,000 exclusive references in the report.

The maps under focused in on the quantity of authors from nations in Africa, Asia-Pacific, Europe, the Middle East, North America and South America.

Country location of all the co-authors from the papers cited in the WG1 report that were published between 2011 and 2020. Maps are shown across Africa (top left), North & Central America (top right), Europe (middle left), the Middle-East (middle right) the Asia-Pacific (bottom left) and South America (bottom right).Nation place of all the co-authors from the papers cited in the WG1 report that have been published in between 2011 and 2020. Maps are shown across Africa (major left), North &amp Central America (major suitable), Europe (middle left), the Middle-East (middle suitable) the Asia-Pacific (bottom left) and South America (bottom suitable). Maps produced employing SciVal. Credit: Félix Chavelli

In most of the maps above, a little quantity of person nations dominate each and every area – for instance South Africa in Africa and Saudi Arabia in the Middle East. The only partial exception is Europe – even though the UK, France and Germany can boast numerous extra authors than their western counterparts.

We also discovered that 99.95% of the cited references have been written in English. We estimate that the final citation list incorporated only 11 non-English language references, with 4 in French, 4 in Spanish, two in German and a single in Portuguese. 

On the other hand, not all references assessed in IPCC reports finish up getting cited in the final solution as the sheer volume of offered literature tends to make it not possible to cite every thing in the report. This signifies that numerous extra papers could have been assessed than these incorporated in our evaluation. 

For instance, the WG1 author survey ran from February to March 2022 and collected feedback from more than 150 WG1 authors and overview editors on the successes, challenges and lessons discovered from the WG1 AR6 knowledge. About 20% of the survey respondents mentioned that non-English literature was assessed in their chapter – like analysis in Arabic, Bangla, Chinese, Farsi, French, German, Italian, Japanese, Portuguese, Russian, Spanish and Ukrainian. 

Topping the tables

The authors of papers cited in the WG1 report hail from extra than two,500 institutions about the globe. The most frequently cited institution is the Centre national de la recherche scientifique (CNRS) – an amalgamation of quite a few institutions primarily based in France, whose specialists contributed virtually 11% of the total citations. 

Virtually all of the major one hundred institutions are primarily based in the international north. Possibly this imbalance is no substantial surprise, taking into consideration the lack of diversity in climate analysis and that the high-priced, resource-intense international climate model analysis centres are predominantly primarily based in international north nations. The regional imbalance in climate analysis filters by way of to an imbalance in the report citations.

The table under shows the major 15 institutions, the nation they are primarily based in and the percentage of citations in the AR6 WG1 report that include things like at least a single author from that institution.

InstitutionNationPercentage of citations

1Centre national de la recherche scientifique (CNRS)France11%

2National Oceanic and Atmospheric Administration (NOAA)US9%

3National Centre for Atmospheric Study (NCAR)US7%

4Université Paris Sciences et LettresFrance7%

5UK Met OfficeUK7%

6Université de ParisFrance7%

7École PolytechniqueFrance7%

8Institute Polytechnique de ParisFrance7%

9Institute de Recherche pour le Développement (IRD)France6%

10Le Commissariat à l’Energie Atomique et aux Energies Options (CEA)France6%

11Swiss Federal Institute of Technologies ZurichSwitzerland6%

12Columbia UniversityUS5%

13Chinese Academy of SciencesChina5%

14Centre National d’Etudes Spatiales (CNES)France5%

15University of ReadingUK5%

The major 15 most represented institutions in the WG1 references and the percentage of the citations inside which they seem.

We also looked at which journals have been cited most often. Virtually all of the WG1 citations are scientific articles, which are published in peer-reviewed, academic journals. (Meanwhile, four% are classified as technical reports or books – identified as “grey literature”.)

In total, there are extra than 800 exclusive journals represented in the WG1 list of citations. The table under shows the ten most hugely cited journals across the references. It incorporates the nation that the publisher is primarily based in and no matter whether the journal is open-access – which means that any individual can access papers published in the journal for no cost.

JournalQuantity of instances citedNation
Open access by default?

1Geophysical Study Letters1.561USYes, as of Jan 2023

2Journal of Climate1,537USAfter a single year

3Climate Dynamics1,075GermanyNo

4Nature Climate Change740GermanyNo

5Environmental Study Letters618UKYes

6Nature 531GermanyNo

7International Journal of Climatology516USNo

8Atmospheric Chemistry and Physics490GermanyYes

9Nature Geoscience 424GermanyNo

10Proceedings of the National Academy of Sciences416USAfter six months

The major ten most hugely cited journals discovered in the IPCC WG1 citation list, noting their corresponding publisher and no matter whether they are open access by default.

The most hugely cited journal across all chapters was Geophysical Study Letters with 1,561 citations in the WG1 references, corresponding to about 1,200 exclusive papers. 

Most of these ten journals are not open-access by default or call for authors to spend further costs for their paper to be an open-access publication. Subscriptions and processing costs can be a substantial barrier to participation for academics, especially for these from the international south. 

The push towards open-access science does not generally lessen up-front publication costs for researchers, but does permit for the final material to be accessed for no cost. Universities and researchers are nevertheless paying higher costs to access and publish their analysis in spite of numerous objections. 


To discover which subject regions are most frequently cited, we utilized a tool named SciVal to automatically assign subject labels to each and every of the WG1 citations. The WG1 literature basis has hyperlinks to a surprisingly broad choice of analysis themes.

This is illustrated in the figure under, which shows a wheel of analysis disciplines and exactly where clusters of these assigned WG1 citation subjects match. Every single dot represents a precise cluster of subjects and its size indicates the quantity of instances they seem in the WG1 citations. The colour corresponds to the scientific discipline that subject is related with, as assigned by SciVal.

WG1 report citations categorised into ‘clusters’ of research topics.WG1 report citations categorised into ‘clusters’ of analysis subjects. All subjects and how they are clustered are automatically assigned by SciVal. Dots represent a precise cluster of subjects. The size of the dots represent the quantity of instances that cluster seems in the WG1 references. The colour corresponds to the scientific discipline that the subject is related with. Scientific disciplines are divided up into the list shown in the bottom panel. Map produced employing SciVal. Credit: Félix Chavelli

Additional than half of all WG1 citations are linked with the subject cluster “Climate models, Model, Rain”, which sits amongst the physical, chemical and environmental science disciplines, and is illustrated by the massive light green circle in the figure.

Quite a few citations are linked to analysis disciplines not generally related with the WG1 report, but these reflect a increasing interest in the cross-disciplinary nature of climate modify – even in a report primarily based on the physical science of climate modify.

For instance, the subject cluster “Salmonella, Escherichia Coli, Listeria Monocytogenes”, which incorporates citations classified beneath the health-related analysis discipline, but in truth covers how physical climate qualities such as temperature can alter illnesses. In yet another instance, “Tourism, Vacationers, Destination” is a cluster linked to the company scientific discipline that incorporates citations covering climate solutions linked to snowfall projections for ski resorts.

Ultimately, we explored the variations in citations in between chapters. Following on from the introduction in Chapter 1, the WG1 report is split in 3 sections:

  • Substantial-scale climate modify (Chapters 2–4)
  • Climate program elements and processes (Chapters 5–9)
  • Regional climate info (Chapters ten-Atlas)
  • Of the 13,000 citations in the report, about four,500 are cited in numerous chapters. About two,000 references are cited in two chapters, more than 500 seem in 3 chapters and just more than 200 are cited in 4 or extra chapters.

    Due to their related themes, chapters eight (“Water cycle changes”) and 11 (“Weather and climate intense events in a altering climate”), 11 and 12 (“Climate modify info for regional effect and for threat assessment”) and eight and ten (“Linking international to regional climate change”) share the most citations.

    For extra info on the IPCC WG1 references and this evaluation, verify out the accompanying report or you can download the citations your self from the WG1 web-site.

    Unique thank you to Robin Matthews, former senior science officer at the Functioning Group I Technical Assistance Unit, for his high quality manage of the WG1 chapter citation lists.

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