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

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

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

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

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

Nonetheless, it also shows that citations in the report are heavily dominated by the international north and normally sit behind a paywall.

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

When and exactly where?

The IPCC’s report on climate science – identified as the Operating Group I (WG1) report – is the initial section of the 3-portion sixth assessment report (AR6). Hundreds of scientists spent years assessing the current literature on climate alter to create this report, which will kind 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 alter and the mitigation of climate alter, 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 had been encouraged to concentrate on offering an update considering the fact that the final cycle, explaining the advances in climate science, how the self-assurance of findings had changed or strengthened and what new subjects had emerged considering the fact that AR5.

We discovered that 98.five% of citations in the AR6 WG1 report had been published considering the fact that the year 2000 and 85% of had been published just after the release of the AR5 in 2013. The chart beneath shows how a lot of citations had been published every single year more than 2000-21.

Year of publication year for all IPCC AR6 WG1 report references published involving 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 just before 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 involving and close to the Tropics, with an try to assign the physical trigger of the stated winds” – was published by English astronomer and mathematician Edmond Halley in 1686.

We also analysed exactly where the authors of every paper had been primarily based at the time of its publication. In total, the 13,500 citations have about 39,000 distinctive authors. Nonetheless, a lot of authors co-authored extra than one particular 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. When 185 nations are represented across the citations, we estimate that extra than 80% of authors are primarily based in the international north. The map beneath illustrates this with a subset of papers published involving 2011 and 2020. The quantity in 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 had been published involving 2011 and 2020. Map made working with SciVal. Credit: Félix Chavelli

3-quarters of all literature cited in the report functions at least one particular author primarily based in either the US or the UK. Extra than six,000 of the references incorporate at least one particular 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 distinctive references in the report.

The maps beneath 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 had been published involving 2011 and 2020. Maps are shown across Africa (best left), North &amp Central America (best appropriate), Europe (middle left), the Middle-East (middle appropriate) the Asia-Pacific (bottom left) and South America (bottom appropriate). Maps made working with SciVal. Credit: Félix Chavelli

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

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

Nonetheless, not all references assessed in IPCC reports finish up becoming cited in the final solution as the sheer volume of out there literature tends to make it not possible to cite all the things in the report. This suggests that a lot of extra papers may possibly have been assessed than these integrated 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 evaluation editors on the successes, challenges and lessons discovered from the WG1 AR6 encounter. About 20% of the survey respondents stated that non-English literature was assessed in their chapter – which includes study 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 planet. The most normally cited institution is the Centre national de la recherche scientifique (CNRS) – an amalgamation of quite a few institutions primarily based in France, whose professionals contributed virtually 11% of the total citations. 

Pretty much all of the best one hundred institutions are primarily based in the international north. Probably this imbalance is no big surprise, thinking about the lack of diversity in climate study and that the highly-priced, resource-intense international climate model study centres are predominantly primarily based in international north nations. The regional imbalance in climate study filters by means of to an imbalance in the report citations.

The table beneath shows the best 15 institutions, the nation they are primarily based in and the percentage of citations in the AR6 WG1 report that incorporate at least one particular 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 best 15 most represented institutions in the WG1 references and the percentage of the citations inside which they seem.

We also looked at which journals had been cited most regularly. Pretty much 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 distinctive journals represented in the WG1 list of citations. The table beneath shows the ten most very cited journals across the references. It involves the nation that the publisher is primarily based in and whether or not the journal is open-access – which means that anybody can access papers published in the journal for totally free.

JournalQuantity of instances citedNation
Open access by default?

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

2Journal of Climate1,537USAfter one particular 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 best ten most very cited journals discovered in the IPCC WG1 citation list, noting their corresponding publisher and whether or not they are open access by default.

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

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

The push towards open-access science does not often minimize up-front publication costs for researchers, but does permit for the final material to be accessed for totally free. Universities and researchers are nevertheless paying higher costs to access and publish their study in spite of a lot of objections. 


To discover which subject regions are most normally cited, we made use of a tool referred to as SciVal to automatically assign subject labels to every of the WG1 citations. The WG1 literature basis has hyperlinks to a surprisingly broad choice of study themes.

This is illustrated in the figure beneath, which shows a wheel of study disciplines and exactly where clusters of these assigned WG1 citation subjects match. Every 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 study 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 made working with SciVal. Credit: Félix Chavelli

Extra 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.

Several citations are linked to study disciplines not typically related with the WG1 report, but these reflect a increasing interest in the cross-disciplinary nature of climate alter – even in a report primarily based on the physical science of climate alter.

For instance, the subject cluster “Salmonella, Escherichia Coli, Listeria Monocytogenes”, which involves citations classified below the health-related study discipline, but in truth covers how physical climate qualities such as temperature can alter ailments. In one more instance, “Tourism, Vacationers, Destination” is a cluster linked to the business enterprise scientific discipline that involves citations covering climate solutions linked to snowfall projections for ski resorts.

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

  • Massive-scale climate alter (Chapters 2–4)
  • Climate method 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 various 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 comparable themes, chapters eight (“Water cycle changes”) and 11 (“Weather and climate intense events in a altering climate”), 11 and 12 (“Climate alter info for regional influence 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 oneself from the WG1 internet site.

    Specific thank you to Robin Matthews, former senior science officer at the Operating Group I Technical Assistance Unit, for his good quality handle of the WG1 chapter citation lists.

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