Scientists urge parties at COP26 to fully acknowledge the latest and most comprehensive assessment of climate change science, included in the last IPCC reports, especially the Sixth Assessment Report Climate Change 2021: The Physical Science Basis (Climate Report) released in August 2021. We, climate scientists, stress that immediate, strong, rapid, sustained and large-scale actions are necessary to hold global warming to well below 2°C and pursue efforts to limit it to 1.5°C, and thereby limit future risk and needs for adaptation over the next decades to centuries.
COP26 is a historic moment for the fate of climate, societies and ecosystems, because human activities have already warmed the planet by around 1.1°C and future greenhouse gas emissions will determine future additional warming. The Climate Report unequivocally shows the extent of human-induced climate change. Almost half of the carbon dioxide accumulated so far in the atmosphere has been emitted in the last 30 years. Greenhouse gas concentrations are at the highest levels in human history, leading to rates of warming unprecedented in more than 2000 years and unprecedented climate extremes in recent years. Cumulative greenhouse gas emissions to date already commit our planet to key changes of the climate system affecting human society and marine and terrestrial ecosystems, some of which are irreversible for generations to come.
Progress in climate science since the IPCC Fifth Assessment Report (2013, 2014), as assessed in the Special Reports on 1.5°C (2018), on Climate Change and Land (2019), and on Ocean and Cryosphere in a Changing Climate (2019), and the 2021 Climate Report, has shown the implications of global warming in excess of 1.5°C. The remaining CO2 budgets compatible with a stabilisation of global warming at 1.5°C are rapidly shrinking (500, 400, and 300 GtCO2 since early 2020, for probabilities of 50%, 67% and 83%, respectively, of limiting global warming to 1.5°C), and highlight the urgent need for a rapid and sustained decline of global emissions, under consideration of climate justice and equity. Given the current yearly emissions of ca. 40GtCO2/yr, these remaining budgets would be exhausted by ca. 2027 to 2033 in the absence of marked decreases in emissions. This highlights the need for immediate reductions of CO2 emissions to achieve both the temperature goal of the Paris agreement and to also contribute to increased climate resilience.
Thousands of scientists from around the world have worked over several years to deliver the evidence base that underpins the Climate Report, which has undergone worldwide expert and government reviews. We now have the most comprehensive and robust assessment to date of how the climate has changed in the past and how it can change in the future, depending on decisions and actions taken today.
Summary for Policymakers of Climate Report[1]
This is the Climate Report high-level summary of the understanding of the current state of the climate, including how it is changing and the role of human influence, the state of knowledge about possible climate futures, climate information relevant to regions and sectors, and limiting human-induced climate change.
This open letter from the international climate science community is about the importance, role and value of climate science to inform climate policy. It is an initiative to support the use of the latest science assessed by the IPCC in the COP26 decision process and a broader and sustained dialogue that reaches across climate science, stakeholders, policy and the public.
We note that all signatories are self-identified members of the climate community, signing as individuals rather than on behalf of their host institution
Contact persons:
Pep Canadell, Australia (Pep.Canadell@csiro.au)
Christophe Cassou, France (cassou@cerfacs.fr)
Piers Forster, UK (P.M.Forster@leeds.ac.uk)
Nana A.B. Klutse, Ghana (amabrowne@gmail.com)
June-Yi Lee, South Korea (juneyi@pusan.ac.kr)
Joeri Rogelj, Belgium/UK (j.rogelj@imperial.ac.uk)
Maisa Rojas, Chile (maisarojas@uchile.cl)
Sonia I. Seneviratne, Switzerland (sonia.seneviratne@ethz.ch)
(Acknowledgements: We thank the numerous scientists who contributed to the writing of this letter)
[1] IPCC, 2021: Summary for Policymakers. In: Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change [Masson-Delmotte, V., P. Zhai, A. Pirani, S. L. Connors, C. Péan, S. Berger, N. Caud, Y. Chen, L. Goldfarb, M. I. Gomis, M. Huang, K. Leitzell, E. Lonnoy, J.B.R. Matthews, T. K. Maycock, T. Waterfield, O. Yelekçi, R. Yu and B. Zhou (eds.)]. Cambridge University Press. In Press. Available from https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6_WGI_SPM_final.pdf
| Last name | First name | Institution | Country |
| AchutaRao | Krishna | Indian Institute of Technology Delhi | India |
| Aðalgeirsdóttir | Guðfinna | University of Iceland | Iceland |
| Adnan | Muhammad | Global Change Impact Studies Centre (GCISC), Ministry of Climate Change (MoCC) | Pakistan |
| Aldunce | Paulina | University of Chile and Center for Climate and Resilience Research CR2 | Chile |
| Alexander | Lisa | UNSW | Australia |
| Allan | Richard | University of Reading | UK |
| Amjad | Muhammad | Global Change Impact Studies Centre | Pakistan |
| Arias | Paola | Universidad de Antioquia | Colombia |
| Bala | Govindasamy | Indian Institute of Science | India |
| Barimalala | Rondrotiana | University of Cape Town | South Africa |
| Barreiro | Marcelo | Universidad de la Republica | Uruguay |
| Bednar-Friedl | Birgit | University of Graz | Austria |
| Bellouin | Nicolas | University of Reading | United Kingdom |
| Besic | Nikola | AgroParisTech – Centre de Nancy | France |
| Bock | Lisa | DLR, German Aerospace Center | Germany |
| Boé | Julien | CNRS / Cerfacs | France |
| Bras | Nicolas | Université de Lorraine | France |
| Camargo | Suzana | Lamont-Doherty Earth Observatory, Columbia University | United States |
| Camilloni | Ines | University of Buenos Aires/CONICET | Argentina |
| Capet | Xavier | CNRS-LOCEAN | France |
| Cassou | Christophe | CNRS-Cerfacs | France |
| Castellanos | Edwin | Universidad del Valle de Guatemala | Guatemala |
| CAUD | Nada | LSCE IPSL | France |
| Cerezo Mota | Ruth | UNAM | Mexico |
| Cernusak | Lucas | James Cook University | Australia |
| Chen | Deliang | University of Gothenburg | Sweden |
| Cherchi | Annalisa | CNR-ISAC | Italy |
| Christian | PIEDALLU | AgroParisTech | France |
| Ciais | Philippe | LSCE | France |
| Cobb | Kim | Georgia Institute of Technology | USA |
| Collins | William | University of Reading | United Kingdom |
| Coppola | Erika | The Abdus Salam International Centre for Theoretical Physics | Italy |
| Corti | Susanna | Institute of Atmospheric Sciences and Climate (CNR-ISAC) | Italy |
| Cotrim da Cunha | Leticia | UERJ | Brazil |
| Cramer | Wolfgang | CNRS-IMBE | France |
| Cruz | Faye Abigail | Manila Observatory | Philippines |
| Cuntz | Matthias | INRAE – Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement | France |
| Cuvi | Nicolás | Facultad Latinoamericana de Ciencias Sociales (FLACSO Sede Ecuador) | Ecuador |
| de Lavergne | Casimir | Sorbonne University | France |
| Dereczynski | Claudine | Federal University of Rio de Janeiro | Brazil |
| Deshayes | Julie | CNRS | France |
| Di Luca | Alejandro | Université du Québec à Montréal | Canada |
| Diongue-Niang | Aïda | Global Green Growth Institute | Sénégal |
| Doblas-Reyes | Francisco | Barcelona Supercomputing Center and ICREA | Spain |
| Domec | Jean-Christophe | Bordeaux Sciences Agro | France |
| Domingues | Catia | National Oceanography Centre | UK |
| Donat | Markus | Barcelona Supercomputing Center | Spain |
| Douville | Hervé | Centre National de Recherches Météorologiques | France |
| Drevillon | Marie | Mercator Ocean International | France |
| Drijfhout | Sybren | Royal Netherlands Meteorological Institute | the Netherlands |
| Durack | Paul | PCMDI/LLNL | USA |
| Ebi | Kristie | University of Washington | USA |
| Edwards | Paul N. | Stanford University | USA |
| Epron | Daniel | Kyoto University – Université de Lorraine | Japan |
| Eyring | Veronika | DLR / University of Bremen | Germany |
| Faria | Sergio Henrique | Basque Centre for Climate Change (BC3) | Spain |
| Farneti | Riccardo | The Abdus Salam International Centre for Theoretical Physics | Italy |
| FERET | Jean-Baptiste | INRAE | France |
| Fischlin | Andreas | IPCC Vice-chair WGII, ETH Zurich | Switzerland |
| Fisher | Ben | University of Edinburgh | United Kingdom |
| Forster | Piers | University of Leeds | UK |
| Fowler | Hayley | Newcastle University | United Kingdom |
| Friedlingstein | Pierre | University of Exeter | United Kingdom |
| Fuzzi | Sandro | Institute of Atmospheric Sciences and Climate – National Research Council | Italy |
| Gallardo | Laura | Universidad de Chile | Chile |
| Gan | Thian Yew | University of Alberta | Canada |
| Garric | Gilles | Mercator Ocean International | France |
| Gentine | Pierre | Columbia university | USA |
| Gergis | Joelle | Australian National University | Australia |
| Ghosh | Subimal | Indian Institute of Technology Bombay | India |
| Gimeno | Teresa | Basque Centre for Climate Change | Spain |
| Giorgi | Filippo | Abdus Salam International Centre for Theoretical Physics (ICTP)s | Italy |
| Giuliani | Graziano | The Abdus Salam centre for theoretical physics | Italy |
| Golledge | Nicholas | Victoria University of Wellington | New Zealand |
| González | Humberto | Universidad Austral de Chile | Chile |
| Goodess | Clare | University of East Anglia | UK |
| Goosse | Hugues | Universite catholique de Louvain | Belgium |
| Gorgues | Thomas | LOPS/IRD | France |
| Gorodetskaya | irina | CESAM, University of Aveiro | Portugal |
| Grace | John | University of Edinburgh | UK |
| Grose | Michael | CSIRO | Australia |
| Gruber | Nicolas | ETH Zürich | Switzerland |
| Guerra Carrillo | Melania | University for Peace | Costa Rica |
| Guillén Bolaños | Tania | Climate Service Center Germany (GERICS), Helmholtz-Zentrum Hereon | Germany |
| Guiot | Joel | CNRS | France |
| Guivarch | Céline | CIRED, Ecole des Ponts | France |
| Gutiérrez | José Manuel | Consejo Superior de Investigaciones Científicas | Spain |
| Gutowski | William | Iowa State University | USA |
| Haarsma | Rein | Royal Netherlands Meteorological Institute (KNMI) | Netherlands |
| Hamdi | Rafiq | Royal Meteorological Institute | Belgium |
| Harris | Neil | Cranfield University | UK |
| Hawkins | Ed | National Centre for Atmospheric Science, University of Reading | UK |
| Hegerl | Gabriele | University of Edinburgh | United Kingdom |
| Henson | Stephanie | National Oceanography Centre | UK |
| Hewitson | Bruce | University of Cape Town | South Africa |
| Hoegh-Guldberg | Ove | University of Queensland | Australia |
| Hope | Pandora | Bureau of Meteorology | Australia |
| Huggel | Christian | University of Zurich | Switzerland |
| Huybrechts | Philippe | Vrije Universiteit Brussel | Belgium |
| Iles | Carley | CICERO | Norway |
| Iskandar | Iskhaq | Department of Physics, University of Sriwijaya | Indonesia |
| Jaccard | Samuel | University of Lausanne | Switzerland |
| Jamero | Ma. Laurice | Manila Observatory | Philippines |
| Jeandel | Catherine | CNRS, LEGOS, Toulouse | France |
| Joos | Fortunat | Climate and Environmental Physics, University of Bern | Switzerland |
| Jouzel | Jean | French Academy of Sciences | France |
| Kaufman | Darrell | Northern Arizona University | USA |
| Kiendler-Scharr | Astrid | Forschungszentrum Jülich GmbH | Germany |
| Kirchengast | Gottfried | University of Graz – Wegener Center for Climate and Global Change | Austria |
| Klimont | Zbigniew | International Institute for Applied Systems Analysis (IIASA) | Austria |
| Klutse | Nana Ama Browne | University of Ghana | Ghana |
| Knutti | Reto | ETH Zurich | Switzerland |
| Kopp | Robert | Rutgers University | United States |
| Kosaka | Yu | Research Center for Advanced Science and Technology, The University of Tokyo | Japan |
| Kossin | James | University of Wisconsin – Madison | USA |
| Koven | Charles | Lawrence Berkeley Lab | United States |
| Krakovska | Svitlana | Ukrainian Hydrometeorological Institute | Ukraine |
| Krinner | Gerhard | IGE/CNRS | France |
| Kucharski | Fred | Abdus Salam International Centre for Theoretical Physics | Italy |
| Lafont | Sébastien | INRAE | France |
| Lawrencen | Daavid | National Center for Atmospheric Research | United States |
| Le Quéré | Corinne | University of East Anglia (UEA) | United Kingdom |
| Lee | June Yi | Research Center for Climate Sciences, Pusan National University | Republic of Korea |
| Lellouche | Jean-Michel | Mercator Ocean International | France |
| Levy | Claire | CNRS | France |
| Lhermitte | Stef | Delft University of Technology | Netherlands |
| Lohmann | Ulrike | ETH Zurich | Switzerland |
| LOUSTAU | DENIS | INRAE | FRANCE |
| Maraun | Douglas | University of Graz, Wegener Center for Climate and Global Change | Austria |
| Marotzke | Jochem | Max Planck Institute for Meteorology | Germany |
| Marquet | Pablo | Pontificia Universidad Católica de Chile | Chile |
| Martinez Castro | Daniel | Instituto Nacional de Investigación en Glaciares y Ecosistemas de Montañai | Peru |
| Masson-Delmotte | Valérie | IPSL/LSCE, Université Paris Saclay | France |
| Massonnet | François | Université catholique de Louvain | Belgium |
| Matthews | Damon | Concordia University | Canada |
| Maycock | Amanda | University of Leeds | UK |
| McElwain | Jennifer | Trinity College Dublin | Ireland |
| McGregor | Shayne | Monash University | Australia |
| Mearns | Linda | National Center for Atmospheric Research | United States |
| Mercado | Lina | University of Exeter | UK |
| Mignot | Juliette | LOCEAN/IRD | France |
| Min | Seung-Ki | Pohang University of Science and Technology | Republic of Korea |
| Mitchell | Dann | University of Bristol | United Kingdom |
| Monteiro | Pedro | CSIR | South Africa |
| Morgenstern | Olaf | National Institute of Water and Atmospheric Research | New Zealand |
| Muniz Alves | Lincoln | National Institute for Space Research (INPE) | Brazil |
| Mustafa | Sawsan | Ministry of Agriculture and Forests | Sudan |
| Ngo-Duc | Thanh | University of Science and Technology of Hanoi | Viet Nam |
| Notz | Dirk | Universität Hamburg | Germany |
| Nowicki | Sophie | University at Buffalo | USA |
| Ogée | Jerome | INRAE | France |
| Ometto | Jean | National Institute for Space Research (INPE) | Brazil |
| Osborn | Tim | University of East Anglia (UEA) | UK |
| Ossó | Albert | Wegener Center for Climate and Global Change | Austria |
| Otto | Friederike | Grantham Institute, Imperial College London | UK |
| Panickal | Swapna | Indian Institute of Tropical Meteorology, Pune | India |
| Patra | Prabir | Research Institute for Global Change, JAMSTEC | Japan/India |
| Pattyn | Frank | Université libre de Bruxelles | Belgium |
| Perkins-Kirkpatrick | Sarah | UNSW Canberra | Australia |
| Pétriacq | Pierre | Université de Bordeaux-INRAE | France |
| Pinto | Izidine | University of Cape Town | South Africa |
| Pitman | Andrew | University of New South Wales | Australia |
| Planquette | Hélène | CNRS – LEMAR – Plouzané | France |
| Plattner | Gian-Kasper | Swiss Federal Institute for Forest, Snow and Landscape Research WSL | Switzerland |
| Pokam Mba | Wilfried | University of Yaounde 1 | Cameroon |
| Pongratz | Julia | Ludwig Maximilian University Munich | Germany |
| Rabarijaona | Arivoara | INRAE | France |
| Raghavan | Krishnan | Indian Institute of Tropical Meteorology | India |
| Rahimi | Mohammad | Semnan University, Faculty of Desert Studies | I. R. of Iran |
| Rathgeber | Cyrille B. K. | INRAE | France |
| Rebetez | Martine | University of Neuchatel and Swiss Federal Research Institute WSL | Switzerland |
| Renwick | James | Victoria University of Wellington | New Zealand |
| Rivera | Juan | IANIGLA/CONICET | Argentina |
| Rochoux | Mélanie | Cerfacs/CNRS | France |
| Rogelj | Joeri | Imperial College London / IIASA | Belgium |
| Rojas | Maisa | Univ of Chile | Chile |
| Rosenfeld | Daniel | The Hebrew University of Jerusalem | Israel |
| Ruiz-Carrascal | Daniel | Columbia University in the City of New York | USA/Colombia |
| Rusticucci | Matilde | Universidad de Buenos Aires | Argentina |
| Sallée | Jean-Baptiste | CNRS | France |
| Sanchez-Gomez | Emilia | Cerfacs-CNRS | FRANCE |
| Satoh | Masaki | Atmosphere and Ocean Research Institute, The University of Tokyo | Japan |
| Seneviratne | Sonia I. | ETH Zurich | Switzerland |
| Sherwood | Steven | Climate Change Research Centre, UNSW Sydney | Australia |
| Sillmann | Jana | CICERO | Norwegen |
| Smith | Chris | University of Leeds | UK |
| Solman | Silvina Alicia | University of Buenos Aires/CONICET | Argentina |
| Solomon | Susan | Massachusetts Institute of Technology | USA |
| Sörensson | Anna | University of Buenos Aires | Argentina |
| Stehr | Alejandra | University of Concepción | Chile |
| Steiner | Andrea K. | Wegener Center for Climate and Global Change, University of Graz | Austria |
| Steininger | Karl | University of Graz | Austria |
| Stocker | Thomas | Physics Institute, University of Bern | Switzerland |
| Stoffel | Markus | University of Geneva | Switzerland |
| Stott | Peter | University of Exeter | UK |
| Swingedouw | Didier | CNRS-EPOC | France |
| Sylla | Mouhamadou Bamba | African Institute for Mathematical Sciences, Kigali | Rwanda |
| Szopa | Sophie | Laboratoire des Sciences du Climat et de l’Environnement | France |
| Taylor | Michael | University of the West Indies | Jamaica |
| Terray | Laurent | Cerfacs/CNRS | France |
| Thiery | Wim | Vrije Universiteit Brussel | Belgium |
| TREGUER | Paul | European Institute for Marine Studies (IUEM/UBO) | France |
| Trenberth | Kevin | NCAR | New Zealand |
| Trigo | Isabel | IPMA | Portugal |
| Turner | Andrew | National Centre for Atmospheric Science, University of Reading | United Kingdom |
| Unger | Nadine | Nanajing University of Information Science and Technology | UK / USA |
| van den Hurk | Bart | Deltares | Netherlands |
| van Ypersele | Jean-Pascal | Université catholique de Louvain (UCLouvain) | Belgium |
| Vera | Carolina | University of Buenos Aires | Argentina |
| Vicca | Sara | University of Antwerp | Belgium |
| Vicente-Serrano | Sergio M. | Consejo Superior de Investigaciones Científicas | Spain |
| Vicuna | Sebastian | Centro de Cambio Global – Universidad Catolica | Chile |
| von Schuckmann | Karina | Mercator Ocean international | France |
| Wild | Martin | ETH Zurich | Switzerland |
| Wingate | Lisa | INRAE | France |
| Yohan | Ruprich-Robert | Barcelona Supercomputing Center | Spain |
| Yoon | Jin-Ho | Gwangju Institute of Science and Technology (GIST) | South Korea |
| Zaehle | Sönke | Max Planck Institute for Biogeochemistry | Germany |