Climate Model Confirmation: From Philosophy to Predicting Climate in the Real World

  • Reto Knutti


Philosophical perspectives on numerical models help us to understand concepts, but will not predict the climate in the future. Studying climate model results in isolation on the other hand may seduce us to believe what we simulate will actually happen. A model is neither correct nor wrong as such; it is simply more or less useful as a representational tool for a certain purpose. I argue that process understanding is the key to make judgments about when this tool is adequate for insight relevant to certain aspects of the real world. It is only through understanding the relationships in components and variables of the climate and their representation in models, combined with understanding what our models are supposed to do, that we can make better use of them.



I thank Christoph Baumberger, Gertrude Hirsch Hadorn, Lisa Lloyd, Maria Rugenstein, Wendy Parker, and Eric Winsberg for constructive comments and discussions, which have helped to clarify my thinking and have greatly improved this manuscript.


  1. Allen, Myles R., Peter A. Stott, John F.B. Mitchell, Reiner Schnur, and Thomas L. Delworth. 2000. Quantifying the Uncertainty in Forecasts of Anthropogenic Climate Change. Nature 407 (6804): 617–620.CrossRefGoogle Scholar
  2. Annan, J.D., and J.C. Hargreaves. 2011. Understanding the CMIP3 Multimodel Ensemble. Journal of Climate 24 (16): 4529–4538.Google Scholar
  3. Boé, Julien, Alex Hall, and Xin Qu. 2009. September Sea-Ice Cover in the Arctic Ocean Projected to Vanish by 2100. Nature Geoscience 2 (5): 341–343.CrossRefGoogle Scholar
  4. Boer, G.J., M. Stowasser, and K. Hamilton. 2007. Inferring Climate Sensitivity from Volcanic Events. Climate Dynamics 28 (5): 481–502.CrossRefGoogle Scholar
  5. Bony, Sandrine, Robert Colman, Vladimir M. Kattsov, Richard P. Allan, Christopher S. Bretherton, Jean-Louis Dufresne, Alex Hall, et al. 2006. How Well Do We Understand and Evaluate Climate Change Feedback Processes? Journal of Climate 19 (15): 3445–3482.CrossRefGoogle Scholar
  6. Braconnot, Pascale, Sandy P. Harrison, Masa Kageyama, Patrick J. Bartlein, Valerie Masson-Delmotte, Ayako Abe-Ouchi, Bette Otto-Bliesner, and Yan Zhao. 2012. Evaluation of Climate Models Using Palaeoclimatic Data. Nature Climate Change 2 (6): 417–424.CrossRefGoogle Scholar
  7. Caldwell, Peter M., Christopher S. Bretherton, Mark D. Zelinka, Stephen A. Klein, Benjamin D. Santer, and Benjamin M. Sanderson. 2014. Statistical Significance of Climate Sensitivity Predictors Obtained by Data Mining. Geophysical Research Letters 41 (5): 1803–1808.CrossRefGoogle Scholar
  8. Claussen, Martin, L. Mysak, A. Weaver, Michel Crucifix, Thierry Fichefet, M.-F. Loutre, S. Weber, et al. 2002. Earth System Models of Intermediate Complexity: Closing the Gap in the Spectrum of Climate System Models. Climate Dynamics 18 (7): 579–586.CrossRefGoogle Scholar
  9. Collins, Matthew, Reto Knutti, Julie Arblaster, J.-L. Dufresne, Thierry Fichefet, Pierre Friedlingstein, Xuejie Gao, et al. 2013. Long-Term Climate Change: Projections, Commitments and Irreversibility. In Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change, 1029–1136. Cambridge/New York: Cambridge University Press.Google Scholar
  10. Cox, Peter M., David Pearson, Ben B. Booth, Pierre Friedlingstein, Chris Huntingford, Chris D. Jones, and Catherine M. Luke. 2013. Sensitivity of Tropical Carbon to Climate Change Constrained by Carbon Dioxide Variability. Nature 494 (7437): 341–344.CrossRefGoogle Scholar
  11. Curry, Judith A., and Peter J. Webster. 2011. Climate Science and the Uncertainty Monster. Bulletin of the American Meteorological Society 92 (12): 1667–1682.CrossRefGoogle Scholar
  12. DelSole, Timothy, and Jagadish Shukla. 2009. Artificial Skill Due to Predictor Screening. Journal of Climate 22 (2): 331–345.CrossRefGoogle Scholar
  13. Deser, Clara, Reto Knutti, Susan Solomon, and Adam S. Phillips. 2012a. Communication of the Role of Natural Variability in Future North American Climate. Nature Climate Change 2 (11): 775–779.CrossRefGoogle Scholar
  14. Deser, Clara, Adam Phillips, Vincent Bourdette, and Haiyan Teng. 2012b. Uncertainty in Climate Change Projections: The Role of Internal Variability. Climate Dynamics 38 (3–4): 527–546.CrossRefGoogle Scholar
  15. Dessai, Suraje, and Mike Hulme. 2004. Does Climate Adaptation Policy Need Probabilities? Climate Policy 4 (2): 107–128.CrossRefGoogle Scholar
  16. Fasullo, John T., and Kevin E. Trenberth. 2012. A Less Cloudy Future: The Role of Subtropical Subsidence in Climate Sensitivity. Science 338 (6108): 792–794.CrossRefGoogle Scholar
  17. Fischer, E.M., and R. Knutti. 2013. Robust Projections of Combined Humidity and Temperature Extremes. Nature Climate Change 3 (2): 126–130.CrossRefGoogle Scholar
  18. Fischer, Erich M., Urs Beyerle, and Reto Knutti. 2013. Robust Spatially Aggregated Projections of Climate Extremes. Nature Climate Change 3 (12): 1033–1038.CrossRefGoogle Scholar
  19. Flato, Gregory, Jochem Marotzke, Babatunde Abiodun, Pascale Braconnot, Sin Chan Chou, William J. Collins, Peter Cox, et al. 2013. Evaluation of Climate Models. In: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Climate Change 2013 5: 741–866.Google Scholar
  20. Frame, D.J., D.A. Stone, P.A. Stott, and M.R. Allen. 2006. Alternatives to Stabilization Scenarios. Geophysical Research Letters 33 (14).
  21. Gleckler, P.J., T.M.L. Wigley, B.D. Santer, J.M. Gregory, K. AchutaRao, and K.E. Taylor. 2006. Volcanoes and Climate: Krakatoa’s Signature Persists in the Ocean. Nature 439 (7077): 675–675.CrossRefGoogle Scholar
  22. Gleckler, P.J., K.E. Taylor, and C. Doutriaux. 2008. Performance Metrics for Climate Models. Journal of Geophysical Research: Atmospheres 113 (D6): D06104. Scholar
  23. Gleckler, P.J., K.E. Taylor, and C. Doutriaux. 2008. Performance Metrics for Climate Models. Journal of Geophysical Research 113: 1–20. Scholar
  24. Hall, Alex, and Xin Qu. 2006. Using the Current Seasonal Cycle to Constrain Snow Albedo Feedback in Future Climate Change. Geophysical Research Letters 33 (3).
  25. Hargreaves, J.C., and J.D. Annan. 2009. On the Importance of Paleoclimate Modelling for Improving Predictions of Future Climate Change. Climate of the Past 5 (4): 803–814.CrossRefGoogle Scholar
  26. Hawkins, Ed, and Rowan Sutton. 2009. The Potential to Narrow Uncertainty in Regional Climate Predictions. Bulletin of the American Meteorological Society 90 (8): 1095–1107.CrossRefGoogle Scholar
  27. ———. 2011. The Potential to Narrow Uncertainty in Projections of Regional Precipitation Change. Climate Dynamics 37 (1–2): 407–418.CrossRefGoogle Scholar
  28. Held, Isaac M. 2005. The Gap Between Simulation and Understanding in Climate Modeling. Bulletin of the American Meteorological Society 86 (11): 1609–1614.CrossRefGoogle Scholar
  29. Held, Isaac. 2014. Simplicity Amid Complexity. Science 343 (6176): 1206–1207. Scholar
  30. Huber, Markus, and Reto Knutti. 2012. Anthropogenic and Natural Warming Inferred from Changes in Earth’s Energy Balance. Nature Geoscience 5 (1): 31–36.CrossRefGoogle Scholar
  31. Huber, Markus, Irina Mahlstein, Martin Wild, John Fasullo, and Reto Knutti. 2011. Constraints on Climate Sensitivity from Radiation Patterns in Climate Models. Journal of Climate 24 (4): 1034–1052.CrossRefGoogle Scholar
  32. Jun, Mikyoung, Reto Knutti, and Douglas W. Nychka. 2008. Local Eigenvalue Analysis of CMIP3 Climate Model Errors. Tellus A 60 (5): 992–1000.CrossRefGoogle Scholar
  33. Kiehl, Jeffrey T. 2007. Twentieth Century Climate Model Response and Climate Sensitivity. Geophysical Research Letters 34 (22).
  34. Knutti, Reto. 2008a. Should We Believe Model Predictions of Future Climate Change? Philosophical Transactions of the Royal Society of London A: Mathematical, Physical and Engineering Sciences 366 (1885): 4647–4664.CrossRefGoogle Scholar
  35. ———. 2008b. Why Are Climate Models Reproducing the Observed Global Surface Warming So Well? Geophysical Research Letters 35 (18).
  36. ———. 2010. The End of Model Democracy? Climatic Change 102 (3–4): 395–404.CrossRefGoogle Scholar
  37. Knutti, Reto, and Gabriele C. Hegerl. 2008. The Equilibrium Sensitivity of the Earth’s Temperature to Radiation Changes. Nature Geoscience 1 (11): 735–743.CrossRefGoogle Scholar
  38. Knutti, Reto, and Jan Sedláček. 2013. Robustness and Uncertainties in the New CMIP5 Climate Model Projections. Nature Climate Change 3 (4): 369–373.CrossRefGoogle Scholar
  39. Knutti, Reto, Thomas F. Stocker, and Daniel G. Wright. 2000. The Effects of Subgrid-Scale Parameterizations in a Zonally Averaged Ocean Model. Journal of Physical Oceanography 30 (11): 2738–2752.CrossRefGoogle Scholar
  40. Knutti, Reto, Thomas F. Stocker, Fortunat Joos, and Gian-Kasper Plattner. 2002. Constraints on Radiative Forcing and Future Climate Change from Observations and Climate Model Ensembles. Nature 416 (6882): 719–723.CrossRefGoogle Scholar
  41. Knutti, Reto, Gerald A. Meehl, Myles R. Allen, and David A. Stainforth. 2006. Constraining Climate Sensitivity from the Seasonal Cycle in Surface Temperature. Journal of Climate 19 (17): 4224–4233.CrossRefGoogle Scholar
  42. Knutti, Reto, Gabriel Abramowitz, Matthew Collins, Veronika Eyring, Peter J. Gleckler, Bruce Hewitson, and Linda Mearns. 2010a. Good Practice Guidance Paper on Assessing and Combining Multi Model Climate Projections. In Meeting Report of the Intergovernmental Panel on Climate Change Expert Meeting on Assessing and Combining Multi Model Climate Projections, ed. Thomas Stocker, Qin Dahe, G.K. Plattner, M. Tignor, and P.M. Midgley. Bern: IPCC Working Group I Technical Support Unit, University of Bern, Switzerland.Google Scholar
  43. Knutti, Reto, Reinhard Furrer, Claudia Tebaldi, Jan Cermak, and Gerald A. Meehl. 2010b. Challenges in Combining Projections from Multiple Climate Models. Journal of Climate 23 (10): 2739–2758.Google Scholar
  44. Knutti, Reto, David Masson, and Andrew Gettelman. 2013. Climate Model Genealogy: Generation CMIP5 and How We Got There. Geophysical Research Letters 40 (6): 1194–1199.CrossRefGoogle Scholar
  45. Lahsen, Myanna. 2005. Seductive Simulations? Uncertainty Distribution Around Climate Models. Social Studies of Science 35 (6): 895–922.CrossRefGoogle Scholar
  46. Lean, Judith L. 2010. Cycles and Trends in Solar Irradiance and Climate. Wiley Interdisciplinary Reviews: Climate Change 1 (1): 111–122.Google Scholar
  47. Lean, Judith, Juerg Beer, and Raymond S. Bradley. 1995. Reconstruction of Solar Irradiance Since 1610: Implications for Climate Change. Geophysical Research Letters 22 (23): 3195–3198.CrossRefGoogle Scholar
  48. Lempert, Robert. 2013. Scenarios That Illuminate Vulnerabilities and Robust Responses. Climatic Change 117 (4): 627–646.CrossRefGoogle Scholar
  49. Lenhard, Johannes, and Eric Winsberg. 2010. Holism and Entrenchment in Climate Model Validation. Studies in History and Philosophy of Modern Physics 41: 253–262.CrossRefGoogle Scholar
  50. Lloyd, Elisabeth A. 2009. Varieties of Support and Confirmation of Climate Models. Aristotelian Society Supplementary Volume 83: 213–232. https://doi:10.1111/j.1467-8349.2009.00179.xGoogle Scholar
  51. ———. 2010. Confirmation and Robustness of Climate Models. Philosophy of Science: 971–984.Google Scholar
  52. Lopez, Ana, Claudia Tebaldi, Mark New, Dave Stainforth, Myles Allen, and Jamie Kettleborough. 2006. Two Approaches to Quantifying Uncertainty in Global Temperature Changes. Journal of Climate 19 (19): 4785–4796.CrossRefGoogle Scholar
  53. Mahlstein, I., R. Knutti, S. Solomon, and R.W. Portmann. 2011. Early Onset of Significant Local Warming in Low Latitude Countries. Environmental Research Letters 6: 34009. Scholar
  54. Mahlstein, Irina, Robert W. Portmann, John S. Daniel, Susan Solomon, and Reto Knutti. 2012. Perceptible Changes in Regional Precipitation in a Future Climate. Geophysical Research Letters 39: 1–5.
  55. Masson, D., and R. Knutti. 2011a. Climate Model Genealogy. Geophysical Research Letters 38: L08703. Scholar
  56. Masson, David, and Reto Knutti. 2011b. Spatial-Scale Dependence of Climate Model Performance in the CMIP3 Ensemble. Journal of Climate 24: 2680–2692. Scholar
  57. ———. 2013. Predictor Screening, Calibration, and Observational Constraints in Climate Model Ensembles: An Illustration Using Climate Sensitivity. Journal of Climate 26: 887–898. Scholar
  58. Mauritsen, Thorsten, Bjorn Stevens, Erich Roeckner, Traute Crueger, Monika Esch, Marco Giorgetta, Helmuth Haak, et al. 2012. Tuning the Climate of a Global Model. Journal of Advances in Modeling Earth Systems 4.
  59. McFarlane, Norman. 2011. Parameterizations: Representing Key Processes in Climate Models Without Resolving Them. Wiley Interdisciplinary Reviews: Climate Change 2: 482–497. Scholar
  60. Mearns, Linda O. 2010. The Drama of Uncertainty. Climatic Change 100 (1): 77–85.CrossRefGoogle Scholar
  61. Meinshausen, Malte, Nicolai Meinshausen, William Hare, Sarah C.B. Raper, Katja Frieler, Reto Knutti, David J. Frame, and Myles R. Allen. 2009. Greenhouse-Gas Emission Targets for Limiting Global Warming to 2 °C. Nature 458 (7242): 1158–1162.CrossRefGoogle Scholar
  62. Moss, Richard H., Jae A. Edmonds, Kathy A. Hibbard, Martin R. Manning, Steven K. Rose, Detlef P. Van Vuuren, Timothy R. Carter, et al. 2010. The Next Generation of Scenarios for Climate Change Research and Assessment. Nature 463 (7282): 747–756.CrossRefGoogle Scholar
  63. Mueller, Peter. 2010. Constructing Climate Knowledge with Computer Models. Wiley Interdisciplinary Reviews: Climate Change 1 (4): 565–580.Google Scholar
  64. Oreskes, Naomi, Kristin Shrader-Frechette, Kenneth Belitz, and others. 1994. Verification, Validation, and Confirmation of Numerical Models in the Earth Sciences. Science 263 (5147): 641–646.CrossRefGoogle Scholar
  65. Parker, Wendy S. 2006. Understanding Pluralism in Climate Modeling. Foundations of Science 11 (4): 349–368.CrossRefGoogle Scholar
  66. ———. 2009a. Does Matter Really Matter? Computer Simulations, Experiments, and Materiality. Synthese 169 (3): 483–496.CrossRefGoogle Scholar
  67. ———. 2009b. II—Confirmation and Adequacy-for-Purpose in Climate Modelling. Aristotelian Society Supplementary Volume 83: 233–249. https://doi:10.1111/j.1467-8349.2009.00180.xGoogle Scholar
  68. ———. 2011. When Climate Models Agree: The Significance of Robust Model Predictions. Philosophy of Science 78 (4): 579–600.CrossRefGoogle Scholar
  69. ———. 2013. Ensemble Modeling, Uncertainty and Robust Predictions. Wiley Interdisciplinary Reviews: Climate Change 4 (3): 213–223.Google Scholar
  70. Pennell, Christopher, and Thomas Reichler. 2011. On the Effective Number of Climate Models. Journal of Climate 24 (9): 2358–2367.CrossRefGoogle Scholar
  71. Pirtle, Zachary, Ryan Meyer, and Andrew Hamilton. 2010. What Does It Mean When Climate Models Agree? A Case for Assessing Independence Among General Circulation Models. Environmental Science & Policy 13 (5): 351–361.CrossRefGoogle Scholar
  72. Reichler, Thomas, and Junsu Kim. 2008. How Well do Coupled Models Simulate Today’s Climate? Bulletin of the American Meteorological Society 89 (3): 303–311.CrossRefGoogle Scholar
  73. Rogelj, Joeri, Malte Meinshausen, and Reto Knutti. 2012. Global Warming Under Old and New Scenarios Using IPCC Climate Sensitivity Range Estimates. Nature Climate Change 2 (4): 248–253.CrossRefGoogle Scholar
  74. Rowlands, Daniel J., David J. Frame, Duncan Ackerley, Tolu Aina, Ben B.B. Booth, Carl Christensen, Matthew Collins, et al. 2012. Broad Range of 2050 Warming from an Observationally Constrained Large Climate Model Ensemble. Nature Geoscience 5 (4): 256–260.CrossRefGoogle Scholar
  75. Sanderson, Benjamin M. 2013. On the Estimation of Systematical Error in Regression-Based Predictions of Climate Sensitivity. Climatic Change 118 (3–4): 757–770.CrossRefGoogle Scholar
  76. Sanderson, Benjamin M., and Reto Knutti. 2012. On the Interpretation of Constrained Climate Model Ensembles. Geophysical Research Letters 39 (16).
  77. Schaller, N., I. Mahlstein, J. Cermak, and R. Knutti. 2011. Analyzing Precipitation Projections: A Comparison of Different Approaches to Climate Model Evaluation. Journal of Geophysical Research: Atmospheres 116 (D10).
  78. Sedláček, Jan, and Reto Knutti. 2014. Half of the World’s Population Experience Robust Changes in the Water Cycle for a 2 °C Warmer World. Environmental Research Letters 9 (4): 44008.CrossRefGoogle Scholar
  79. Sherwood, Steven C., Sandrine Bony, and Jean-Louis Dufresne. 2014. Spread in Model Climate Sensitivity Traced to Atmospheric Convective Mixing. Nature 505 (7481): 37–42.CrossRefGoogle Scholar
  80. Smith, Leonard A. 2002. What Might We Learn from Climate Forecasts? Proceedings of the National Academy of Sciences 99 (suppl 1): 2487–2492.CrossRefGoogle Scholar
  81. Smith, Richard L., Claudia Tebaldi, Doug Nychka, and Linda O. Mearns. 2009. Bayesian Modeling of Uncertainty in Ensembles of Climate Models. Journal of the American Statistical Association 104 (485): 97–116.CrossRefGoogle Scholar
  82. Soden, Brian J., Richard T. Wetherald, Georgiy L. Stenchikov, and Alan Robock. 2002. Global Cooling after the Eruption of Mount Pinatubo: A Test of Climate Feedback by Water Vapor. Science 296 (5568): 727–730.CrossRefGoogle Scholar
  83. Solomon, Susan, Gian-Kasper Plattner, Reto Knutti, and Pierre Friedlingstein. 2009. Irreversible Climate Change Due to Carbon Dioxide Emissions. Proceedings of the National Academy of Sciences 106: 1704–1709. https://doi:10.1073/pnas.0812721106.Google Scholar
  84. Stevens, Bjorn, and Sandrine Bony. 2013. What Are Climate Models Missing? Science 340 (6136): 1053–1054.CrossRefGoogle Scholar
  85. Stott, Peter A., and James A. Kettleborough. 2002. Origins and Estimates of Uncertainty in Predictions of Twenty-First Century Temperature Rise. Nature 416 (6882): 723–726.CrossRefGoogle Scholar
  86. Stott, Peter A., S.F.B. Tett, G.S. Jones, M.R. Allen, J.F.B. Mitchell, and G.J. Jenkins. 2000. External Control of 20th Century Temperature by Natural and Anthropogenic Forcings. Science 290 (5499): 2133–2137.CrossRefGoogle Scholar
  87. Stott, Peter, Peter Good, Gareth Jones, Nathan Gillett, and Ed Hawkins. 2013. The Upper End of Climate Model Temperature Projections Is Inconsistent with Past Warming. Environmental Research Letters 8 (1): 14024.CrossRefGoogle Scholar
  88. Stroeve, Julienne, Marika M. Holland, Walt Meier, Ted Scambos, and Mark Serreze. 2007. Arctic Sea Ice Decline: Faster than Forecast. Geophysical Research Letters 34 (9).
  89. Stroeve, Julienne C., Vladimir Kattsov, Andrew Barrett, Mark Serreze, Tatiana Pavlova, Marika Holland, and Walter N. Meier. 2012. Trends in Arctic Sea Ice Extent from CMIP5, CMIP3 and Observations. Geophysical Research Letters 39 (16).
  90. Taylor, Karl E., Ronald J. Stouffer, and Gerald A. Meehl. 2012. An Overview of CMIP5 and the Experiment Design. Bulletin of the American Meteorological Society 93 (4): 485–498.CrossRefGoogle Scholar
  91. Tebaldi, Claudia, and Reto Knutti. 2007. The Use of the Multi-Model Ensemble in Probabilistic Climate Projections. Philosophical Transactions of the Royal Society of London A: Mathematical, Physical and Engineering Sciences 365 (1857): 2053–2075.CrossRefGoogle Scholar
  92. Tebaldi, Claudia, Linda O. Mearns, Doug Nychka, and Richard L. Smith. 2004. Regional Probabilities of Precipitation Change: A Bayesian Analysis of Multimodel Simulations. Geophysical Research Letters 31 (24).
  93. Tebaldi, Claudia, Richard L. Smith, Doug Nychka, and Linda O. Mearns. 2005. Quantifying Uncertainty in Projections of Regional Climate Change: A Bayesian Approach to the Analysis of Multimodel Ensembles. Journal of Climate 18 (10): 1524–1540.CrossRefGoogle Scholar
  94. Tebaldi, Claudia, Julie M. Arblaster, and Reto Knutti. 2011. Mapping Model Agreement on Future Climate Projections. Geophysical Research Letters 38 (23).
  95. Trenberth, Kevin E., and Aiguo Dai. 2007. Effects of Mount Pinatubo Volcanic Eruption on the Hydrological Cycle as an Analog of Geoengineering. Geophysical Research Letters 34 (15).
  96. Van Oldenborgh, Geert Jan, S.Y. Philip, and Matthew Collins. 2005. El Niño in a Changing Climate: A Multi-Model Study. Ocean Science 1 (2): 81–95.CrossRefGoogle Scholar
  97. Weigel, Andreas P., Reto Knutti, Mark A. Liniger, and Christof Appenzeller. 2010. Risks of Model Weighting in Multimodel Climate Projections. Journal of Climate 23 (15): 4175–4191.CrossRefGoogle Scholar
  98. Weisberg, Michael. 2006. Robustness Analysis. Philosophy of Science 73 (5): 730–742.CrossRefGoogle Scholar

Copyright information

© The Author(s) 2018

Authors and Affiliations

  • Reto Knutti
    • 1
  1. 1.Department of Environmental Systems ScienceInstitute for Atmospheric and Climate Science, ETH ZurichZurichSwitzerland

Personalised recommendations