Incomplete understanding of three aspects of the climate system—equilibrium climate sensitivity, rate of ocean heat uptake and historical aerosol forcing—and the physical processes underlying them lead to uncertainties in our assessment of the global-mean temperature evolution in the twenty-first century1,2. Explorations of these uncertainties have so far relied on scaling approaches3,4, large ensembles of simplified climate models1,2, or small ensembles of complex coupled atmosphere–ocean general circulation models5,6 which under-represent uncertainties in key climate system properties derived from independent sources7,8,9. Here we present results from a multi-thousand-member perturbed-physics ensemble of transient coupled atmosphere–ocean general circulation model simulations. We find that model versions that reproduce observed surface temperature changes over the past 50 years show global-mean temperature increases of 1.4–3 K by 2050, relative to 1961–1990, under a mid-range forcing scenario. This range of warming is broadly consistent with the expert assessment provided by the Intergovernmental Panel on Climate Change Fourth Assessment Report10, but extends towards larger warming than observed in ensembles-of-opportunity5 typically used for climate impact assessments. From our simulations, we conclude that warming by the middle of the twenty-first century that is stronger than earlier estimates is consistent with recent observed temperature changes and a mid-range ‘no mitigation’ scenario for greenhouse-gas emissions.

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We thank all participants in the climateprediction.net experiments, as well as the academic institutions and the individuals who have helped make the experiment possible, particularly D. Anderson for developing the Berkeley Open Infrastructure for Network Computing. We also thank the Natural Environment Research Council (NERC), the European Union FP6 WATCH and ENSEMBLES projects, the Oxford Martin School, the Smith School of Enterprise and the Environment and Microsoft Research for support and J. Renouf and co-workers at the BBC for their documentaries explaining and promoting this experiment. D.J.R. was supported by a NERC PhD studentship with a CASE award from the Centre for Ecology & Hydrology (CEH) Wallingford.

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  1. Atmospheric, Oceanic & Planetary Physics, Department of Physics, University of Oxford, Parks Road, Oxford OX1 3PU, UK

    • Daniel J. Rowlands
    • , David J. Frame
    • , Tolu Aina
    • , Carl Christensen
    • , Nicholas Faull
    • , Benjamin S. Grandey
    • , Edward Gryspeerdt
    • , William J. Ingram
    • , Neil Massey
    • , Suzanne M. Rosier
    • , Kuniko Yamazaki
    • , Y. Hiro Yamazaki
    •  & Myles R. Allen
  2. School of Geography and the Environment, University of Oxford, South Parks Road, Oxford OX1 3QY, UK

    • Daniel J. Rowlands
    • , David J. Frame
    • , Ana Lopez
    •  & Myles R. Allen
  3. Centre for the Analysis of Time Series, London School of Economics, London WC2A 2AE, UK

    • Daniel J. Rowlands
    • , Ana Lopez
    •  & Leonard A. Smith
  4. Smith School of Enterprise and the Environment, Hayes House, 75 George Street, Oxford OX1 2BQ, UK

    • David J. Frame
    • , Neil Massey
    •  & Myles R. Allen
  5. Climate Change Research Institute, School of Geography, Environment and Earth Sciences, Victoria University of Wellington, Wellington 6012, New Zealand

    • David J. Frame
  6. Monash Weather and Climate, Monash University, Clayton, Victoria 3800, Australia

    • Duncan Ackerley
  7. Department of Meteorology, University of Reading, Earley Gate, Reading, RG6 6BB, UK

    • Duncan Ackerley
    •  & Eleanor J. Highwood
  8. Oxford e-Research Centre, Keble Road, Oxford OX1 3QG, UK

    • Tolu Aina
    •  & Milo Thurston
  9. Met Office Hadley Centre, FitzRoy Road, Exeter EX1 3PU, UK

    • Ben B. B. Booth
    •  & William J. Ingram
  10. College of Engineering, Mathematics and Physical Sciences, University of Exeter, Exeter, EX4 4QJ, UK

    • Matthew Collins
  11. Department of Meteorology, Earth and Environmental Systems Institute, Pennsylvania State University, University Park, Pennsylvania 16802, USA

    • Chris E. Forest
  12. Royal Meteorological Society, Reading, RG1 7LL, UK

    • Sylvia Knight
  13. BBC Science, BBC White City, 201 Wood Lane, London W12 7TS, UK

    • Frances McNamara
  14. Department of Statistics, University of Oxford, 1 South Parks Road, Oxford OX1 3TG, UK

    • Nicolai Meinshausen
  15. Abdus Salam International Center for Theoretical Physics, Trieste 34151, Italy

    • Claudio Piani
  16. The American University of Paris, Paris 75007, France

    • Claudio Piani
  17. NIWA Wellington, 301 Evans Bay Parade, Hataitai, Wellington 6021, New Zealand

    • Suzanne M. Rosier
  18. National Center for Atmospheric Research, 1850 Table Mesa Dr, Boulder, Colorado 80305, USA

    • Benjamin M. Sanderson
  19. Pembroke College, Oxford University of Oxford, Oxford OX1 1DW, UK

    • Leonard A. Smith
  20. Climate Systems Analysis Group, University of Cape Town, Private Bag X3, Rondebosch, Cape Town, South Africa

    • Dáithí A. Stone
  21. School of Geography, Politics and Sociology, Newcastle University, Newcastle on Tyne, NE1 7RU, UK

    • Y. Hiro Yamazaki


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All authors contributed to the design and implementation of the experiment. D.J.R. performed the analysis and wrote the paper, with significant contributions from D.J.F., M.R.A. and N.M. All authors commented on the paper.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Daniel J. Rowlands.

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