International climate scientists call for more ambition in final texts

Seven representative scientists are presenting about the letter. Picture from Professor Sonia I. Seneviratne’s twitter. Left corner: ICCP Professor June-Yi Lee

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 (

Christophe Cassou, France (

Piers Forster, UK (

Nana A.B. Klutse, Ghana (

June-Yi Lee, South Korea (

Joeri Rogelj, Belgium/UK (

Maisa Rojas, Chile (

Sonia I. Seneviratne, Switzerland (

(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

Last nameFirst nameInstitutionCountry
AchutaRaoKrishnaIndian Institute of Technology DelhiIndia
AðalgeirsdóttirGuðfinnaUniversity of IcelandIceland
AdnanMuhammadGlobal Change Impact Studies Centre (GCISC), Ministry of Climate Change (MoCC)Pakistan
AlduncePaulinaUniversity of Chile and Center for Climate and Resilience Research CR2Chile
AllanRichardUniversity of ReadingUK
AmjadMuhammadGlobal Change Impact Studies CentrePakistan
AriasPaolaUniversidad de AntioquiaColombia
BalaGovindasamyIndian Institute of ScienceIndia
BarimalalaRondrotianaUniversity of Cape TownSouth Africa
BarreiroMarceloUniversidad de la RepublicaUruguay
Bednar-FriedlBirgitUniversity of GrazAustria
BellouinNicolasUniversity of ReadingUnited Kingdom
BesicNikolaAgroParisTech – Centre de NancyFrance
BockLisaDLR, German Aerospace CenterGermany
BoéJulienCNRS / CerfacsFrance
BrasNicolasUniversité de LorraineFrance
CamargoSuzanaLamont-Doherty Earth Observatory, Columbia UniversityUnited States
CamilloniInesUniversity of Buenos Aires/CONICETArgentina
CastellanosEdwinUniversidad del Valle de GuatemalaGuatemala
Cerezo MotaRuthUNAMMexico
CernusakLucasJames Cook UniversityAustralia
ChenDeliangUniversity of GothenburgSweden
CobbKimGeorgia Institute of TechnologyUSA
CollinsWilliamUniversity of ReadingUnited Kingdom
CoppolaErikaThe Abdus Salam International Centre for Theoretical PhysicsItaly
CortiSusannaInstitute of Atmospheric Sciences and Climate (CNR-ISAC)Italy
Cotrim da CunhaLeticiaUERJBrazil
CruzFaye AbigailManila ObservatoryPhilippines
CuntzMatthiasINRAE – Institut National de Recherche pour l’Agriculture, l’Alimentation et l’EnvironnementFrance
CuviNicolásFacultad Latinoamericana de Ciencias Sociales (FLACSO Sede Ecuador)Ecuador
de LavergneCasimirSorbonne UniversityFrance
DereczynskiClaudineFederal University of Rio de JaneiroBrazil
Di LucaAlejandroUniversité du Québec à MontréalCanada
Diongue-NiangAïdaGlobal Green Growth InstituteSénégal
Doblas-ReyesFranciscoBarcelona Supercomputing Center and ICREASpain
DomecJean-ChristopheBordeaux Sciences AgroFrance
DominguesCatiaNational Oceanography CentreUK
DonatMarkusBarcelona Supercomputing CenterSpain
DouvilleHervéCentre National de Recherches MétéorologiquesFrance
DrevillonMarieMercator Ocean InternationalFrance
DrijfhoutSybrenRoyal Netherlands Meteorological Institutethe Netherlands
EbiKristieUniversity of WashingtonUSA
EdwardsPaul N.Stanford UniversityUSA
EpronDanielKyoto University – Université de LorraineJapan
EyringVeronikaDLR / University of BremenGermany
FariaSergio HenriqueBasque Centre for Climate Change (BC3)Spain
FarnetiRiccardoThe Abdus Salam International Centre for Theoretical PhysicsItaly
FischlinAndreasIPCC Vice-chair WGII, ETH ZurichSwitzerland
FisherBenUniversity of EdinburghUnited Kingdom
ForsterPiersUniversity of LeedsUK
FowlerHayleyNewcastle UniversityUnited Kingdom
FriedlingsteinPierreUniversity of ExeterUnited Kingdom
FuzziSandroInstitute of Atmospheric Sciences and Climate – National Research CouncilItaly
GallardoLauraUniversidad de ChileChile
GanThian YewUniversity of AlbertaCanada
GarricGillesMercator Ocean InternationalFrance
GentinePierreColumbia universityUSA
GergisJoelleAustralian National UniversityAustralia
GhoshSubimalIndian Institute of Technology BombayIndia
GimenoTeresaBasque Centre for Climate ChangeSpain
GiorgiFilippoAbdus Salam International Centre for Theoretical Physics (ICTP)sItaly
GiulianiGrazianoThe Abdus Salam centre for theoretical physicsItaly
GolledgeNicholasVictoria University of WellingtonNew Zealand
GonzálezHumbertoUniversidad Austral de ChileChile
GoodessClareUniversity of East AngliaUK
GoosseHuguesUniversite catholique de LouvainBelgium
GorodetskayairinaCESAM, University of AveiroPortugal
GraceJohnUniversity of EdinburghUK
GruberNicolasETH ZürichSwitzerland
Guerra CarrilloMelaniaUniversity for PeaceCosta Rica
Guillén BolañosTaniaClimate Service Center Germany (GERICS), Helmholtz-Zentrum HereonGermany
GuivarchCélineCIRED, Ecole des PontsFrance
GutiérrezJosé ManuelConsejo Superior de Investigaciones CientíficasSpain
GutowskiWilliamIowa State UniversityUSA
HaarsmaReinRoyal Netherlands Meteorological Institute (KNMI)Netherlands
HamdiRafiqRoyal Meteorological InstituteBelgium
HarrisNeilCranfield UniversityUK
HawkinsEdNational Centre for Atmospheric Science, University of ReadingUK
HegerlGabrieleUniversity of EdinburghUnited Kingdom
HensonStephanieNational Oceanography CentreUK
HewitsonBruceUniversity of Cape TownSouth Africa
Hoegh-GuldbergOveUniversity of QueenslandAustralia
HopePandoraBureau of MeteorologyAustralia
HuggelChristianUniversity of ZurichSwitzerland
HuybrechtsPhilippeVrije Universiteit BrusselBelgium
IskandarIskhaqDepartment of Physics, University of SriwijayaIndonesia
JaccardSamuelUniversity of LausanneSwitzerland
JameroMa. LauriceManila ObservatoryPhilippines
JeandelCatherineCNRS, LEGOS, ToulouseFrance
JoosFortunatClimate and Environmental Physics, University of BernSwitzerland
JouzelJeanFrench Academy of SciencesFrance
KaufmanDarrellNorthern Arizona UniversityUSA
Kiendler-ScharrAstridForschungszentrum Jülich GmbHGermany
KirchengastGottfriedUniversity of Graz – Wegener Center for Climate and Global ChangeAustria
KlimontZbigniewInternational Institute for Applied Systems Analysis (IIASA)Austria
KlutseNana Ama BrowneUniversity of GhanaGhana
KnuttiRetoETH ZurichSwitzerland
KoppRobertRutgers UniversityUnited States
KosakaYuResearch Center for Advanced Science and Technology, The University of TokyoJapan
KossinJamesUniversity of Wisconsin – MadisonUSA
KovenCharlesLawrence Berkeley LabUnited States
KrakovskaSvitlanaUkrainian Hydrometeorological InstituteUkraine
KucharskiFredAbdus Salam International Centre for Theoretical PhysicsItaly
LawrencenDaavidNational Center for Atmospheric ResearchUnited States
Le QuéréCorinneUniversity of East Anglia (UEA)United Kingdom
LeeJune YiResearch Center for Climate Sciences, Pusan National UniversityRepublic of Korea
LelloucheJean-MichelMercator Ocean InternationalFrance
LhermitteStefDelft University of TechnologyNetherlands
LohmannUlrikeETH ZurichSwitzerland
MaraunDouglasUniversity of Graz, Wegener Center for Climate and Global ChangeAustria
MarotzkeJochemMax Planck Institute for MeteorologyGermany
MarquetPabloPontificia Universidad Católica de ChileChile
Martinez CastroDanielInstituto Nacional de Investigación en Glaciares y Ecosistemas de MontañaiPeru
Masson-DelmotteValérieIPSL/LSCE, Université Paris SaclayFrance
MassonnetFrançoisUniversité catholique de LouvainBelgium
MatthewsDamonConcordia UniversityCanada
MaycockAmandaUniversity of LeedsUK
McElwainJenniferTrinity College DublinIreland
McGregorShayneMonash UniversityAustralia
MearnsLindaNational Center for Atmospheric ResearchUnited States
MercadoLinaUniversity of ExeterUK
MinSeung-KiPohang University of Science and TechnologyRepublic of Korea
MitchellDannUniversity of BristolUnited Kingdom
MonteiroPedroCSIRSouth Africa
MorgensternOlafNational Institute of Water and Atmospheric ResearchNew Zealand
Muniz AlvesLincolnNational Institute for Space Research (INPE)Brazil
MustafaSawsanMinistry of Agriculture and ForestsSudan
Ngo-DucThanhUniversity of Science and Technology of HanoiViet Nam
NotzDirkUniversität HamburgGermany
NowickiSophieUniversity at BuffaloUSA
OmettoJeanNational Institute for Space Research (INPE)Brazil
OsbornTimUniversity of East Anglia (UEA)UK
OssóAlbertWegener Center for Climate and Global ChangeAustria
OttoFriederikeGrantham Institute, Imperial College LondonUK
PanickalSwapnaIndian Institute of Tropical Meteorology, PuneIndia
PatraPrabirResearch Institute for Global Change, JAMSTECJapan/India
PattynFrankUniversité libre de BruxellesBelgium
Perkins-KirkpatrickSarahUNSW CanberraAustralia
PétriacqPierreUniversité de Bordeaux-INRAEFrance
PintoIzidineUniversity of Cape TownSouth Africa
PitmanAndrewUniversity of New South WalesAustralia
PlanquetteHélèneCNRS – LEMAR – PlouzanéFrance
PlattnerGian-KasperSwiss Federal Institute for Forest, Snow and Landscape Research WSLSwitzerland
Pokam MbaWilfriedUniversity of Yaounde 1Cameroon
PongratzJuliaLudwig Maximilian University MunichGermany
RaghavanKrishnanIndian Institute of Tropical MeteorologyIndia
RahimiMohammadSemnan University, Faculty of Desert StudiesI. R. of Iran
RathgeberCyrille B. K.INRAEFrance
RebetezMartineUniversity of Neuchatel and Swiss Federal Research Institute WSLSwitzerland
RenwickJamesVictoria University of WellingtonNew Zealand
RogeljJoeriImperial College London / IIASABelgium
RojasMaisaUniv of ChileChile
RosenfeldDanielThe Hebrew University of JerusalemIsrael
Ruiz-CarrascalDanielColumbia University in the City of New YorkUSA/Colombia
RusticucciMatildeUniversidad de Buenos AiresArgentina
SatohMasakiAtmosphere and Ocean Research Institute, The University of TokyoJapan
SeneviratneSonia I.ETH ZurichSwitzerland
SherwoodStevenClimate Change Research Centre, UNSW SydneyAustralia
SmithChrisUniversity of LeedsUK
SolmanSilvina AliciaUniversity of Buenos Aires/CONICETArgentina
SolomonSusanMassachusetts Institute of TechnologyUSA
SörenssonAnnaUniversity of Buenos AiresArgentina
StehrAlejandraUniversity of ConcepciónChile
SteinerAndrea K.Wegener Center for Climate and Global Change, University of GrazAustria
SteiningerKarlUniversity of GrazAustria
StockerThomasPhysics Institute, University of BernSwitzerland
StoffelMarkusUniversity of GenevaSwitzerland
StottPeterUniversity of ExeterUK
SyllaMouhamadou BambaAfrican Institute for Mathematical Sciences, KigaliRwanda
SzopaSophieLaboratoire des Sciences du Climat et de l’EnvironnementFrance
TaylorMichaelUniversity of the West IndiesJamaica
ThieryWimVrije Universiteit BrusselBelgium
TREGUERPaulEuropean Institute for Marine Studies (IUEM/UBO)France
TrenberthKevinNCARNew Zealand
TurnerAndrewNational Centre for Atmospheric Science, University of ReadingUnited Kingdom
UngerNadineNanajing University of Information Science and TechnologyUK / USA
van den HurkBartDeltaresNetherlands
van YperseleJean-PascalUniversité catholique de Louvain (UCLouvain)Belgium
VeraCarolinaUniversity of Buenos AiresArgentina
ViccaSaraUniversity of AntwerpBelgium
Vicente-SerranoSergio M.Consejo Superior de Investigaciones CientíficasSpain
VicunaSebastianCentro de Cambio Global – Universidad CatolicaChile
von SchuckmannKarinaMercator Ocean internationalFrance
WildMartinETH ZurichSwitzerland
YohanRuprich-RobertBarcelona Supercomputing CenterSpain
YoonJin-HoGwangju Institute of Science and Technology (GIST)South Korea
ZaehleSönkeMax Planck Institute for BiogeochemistryGermany