Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Earth system sensitivity inferred from Pliocene modelling and data


Quantifying the equilibrium response of global temperatures to an increase in atmospheric carbon dioxide concentrations is one of the cornerstones of climate research. Components of the Earth’s climate system that vary over long timescales, such as ice sheets and vegetation, could have an important effect on this temperature sensitivity, but have often been neglected. Here we use a coupled atmosphere–ocean general circulation model to simulate the climate of the mid-Pliocene warm period (about three million years ago), and analyse the forcings and feedbacks that contributed to the relatively warm temperatures. Furthermore, we compare our simulation with proxy records of mid-Pliocene sea surface temperature. Taking these lines of evidence together, we estimate that the response of the Earth system to elevated atmospheric carbon dioxide concentrations is 30–50% greater than the response based on those fast-adjusting components of the climate system that are used traditionally to estimate climate sensitivity. We conclude that targets for the long-term stabilization of atmospheric greenhouse-gas concentrations aimed at preventing a dangerous human interference with the climate system should take into account this higher sensitivity of the Earth system.

This is a preview of subscription content, access via your institution

Relevant articles

Open Access articles citing this article.

Access options

Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Figure 1: Charney sensitivity and Earth system sensitivity.
Figure 2: Simulated mid-Pliocene temperature change.
Figure 3: Model–data comparison.


  1. Charney, J. et al. Carbon Dioxide and Climate: A Scientific Assessment (National Research Council, 1979).

    Google Scholar 

  2. Andronova, N. & Schlesinger, M. E. Objective estimation of the probability distribution for climate sensitivity. J. Geophys. Res. 106, 22605–22612 (2001).

    Article  Google Scholar 

  3. Frame, D. J. et al. Constraining climate forecasts: The role of prior assumptions. Geophys. Res. Lett. 32, L09702 (2005).

    Article  Google Scholar 

  4. Annan, J. D. & Hargreaves, J. C. Using multiple observationally-based constraints to estimate climate sensitivity. Geophys. Res. Lett. 33, L06704 (2006).

    Article  Google Scholar 

  5. Hansen, J. et al. in Climate Processes and Climate Sensitivity (eds Hansen, J. E. & Takahashi, T.) 130–163 (American Geophysical Union, 1984).

    Google Scholar 

  6. Slingo, A. Handbook of the Meteorological Office 11-Layer Atmospheric General Circulation Model. Vol. 1: Model Description (UK Meteorological Office, 1985).

    Google Scholar 

  7. Houghton, J. T. et al. (eds) IPCC Climate Change 2001: The Scientific Basis (Cambridge Univ. Press, 2001).

  8. Solomon, S. et al. (eds) IPCC Climate Change 2007: The Physical Science Basis (Cambridge Univ. Press, 2007).

  9. Hansen, J. et al. Target atmospheric CO2: Where should humanity aim? Open Atmospheric Sci. J. 2, 217–231 (2008).

    Article  Google Scholar 

  10. Knutti, R. & Hegerl, G. C. The equilibrium sensitivity of the Earth’s temperature to radiation changes. Nature Geosci. 1, 735–743 (2008).

    Article  Google Scholar 

  11. Martin, J. H. Glacial-interglacial CO2 change: The iron hypothesis. Paleoceanography 5, 1–13 (1990).

    Article  Google Scholar 

  12. Kump, L. R., Brantley, S. L. & Arthur, M. A. Chemical weathering, atmospheric CO2 and climate. Annu. Rev. Earth Planet. Sci. 28, 611–667 (2000).

    Article  Google Scholar 

  13. Ridley, J. K., Huybrechts, P., Gregory, J. M. & Lowe, J. A. Elimination of the Greenland ice sheet in a high CO2 climate. J. Clim. 18, 3409–3427 (2005).

    Article  Google Scholar 

  14. Notaro, M., Vavrus, S. & Liu, Z. Y. Global vegetation and climate change due to future increases in CO2 as projected by a fully coupled model with dynamic vegetation. J. Clim. 20, 70–90 (2007).

    Article  Google Scholar 

  15. Price, S. F., Conway, H., Waddington, E. D. & Bindschadler, R. A. Model investigations of inland migration of fast-flowing outlet glaciers and ice streams. J. Glaciol. 54, 49–60 (2008).

    Article  Google Scholar 

  16. Schoof, C. Ice sheet grounding line dynamics: Steady states, stability, and hysteresis. J. Geophys. Res. 112, F03S38 (2007).

    Article  Google Scholar 

  17. Siegenthaler, U. et al. Stable carbon cycle-climate relationship during the late Pleistocene. Science 310, 1313–1317 (2005).

    Article  Google Scholar 

  18. Raymo, M. E., Grant, B., Horowitz, M. & Rau, G. H. Mid-Pliocene warmth: Stronger greenhouse and stronger conveyor. Mar. Micropaleontol. 27, 313–326 (1996).

    Article  Google Scholar 

  19. Kurschner, W. M., van der Burgh, J., Visscher, H. & Dilcher, D. L. Oak leaves as biosensors of late Neogene and early Pleiostocene paleoatmospheric CO2 concentrations. Mar. Micropaleontol. 27, 299–312 (1996).

    Article  Google Scholar 

  20. Dowsett, H. J. in Deep Time Perspectives on Climate Change: Marrying the Signal from Computer Models and Biological Proxies (eds Williams, M., Haywood, A. M., Gregory, J. F. & Schmidt, D. N.) 459–480 (Micropalaeontological Society Special Publications, Geological Society of London, 2007).

    Book  Google Scholar 

  21. Lisiecki, L. E. & Raymo, M. E. A Pliocene-Pleistocene stack of 57 globally distributed benthic δ18O records. Paleoceanography 20, PA1003 (2005).

    Google Scholar 

  22. Dowsett, H. J. et al. Middle Pliocene paleoenvironmental reconstruction: PRISM2. USGS Open File Report 99-535 <> (1999).

  23. Raymo, M. E., Ruddiman, W. F. & Froelich, P. N. Influence of late Cenozoic mountain building on ocean geochemical cycles. Geology 16, 649–653 (1988).

    Article  Google Scholar 

  24. Thompson, R. S. & Fleming, R. F. Middle Pliocene vegetation: Reconstructions, paleoclimatic inferences, and boundary conditions for climatic modelling. Mar. Micropaleontol. 27, 27–49 (1996).

    Article  Google Scholar 

  25. Haywood, A. M. & Valdes, P. J. Modelling middle Pliocene warmth: Contribution of atmosphere, oceans and cryosphere. Earth Planet. Sci. Lett. 218, 363–377 (2004).

    Article  Google Scholar 

  26. Bony, S. et al. How well do we understand and evaluate climate change feedback processes? J. Clim. 19, 3445–3482 (2006).

    Article  Google Scholar 

  27. Hansen, J. et al. Efficacy of climate forcings. J. Geophys. Res. 110, D18104 (2005).

    Article  Google Scholar 

  28. Gordon, C. et al. The simulation of SST, sea ice extents and ocean heat transports in a version of the Hadley Centre coupled model without flux adjustments. Clim. Dynam. 16, 147–168 (2000).

    Article  Google Scholar 

  29. Covey, C. et al. An overview of results from the Coupled Model Intercomparison Project. Glob. Planet. Change 37, 103–133 (2003).

    Article  Google Scholar 

  30. Sloan, L. C., Crowley, T. J. & Pollard, D. Modeling of middle Pliocene climate with the NCAR GENESIS general circulation model. Mar. Micropaleontol. 27, 51–61 (1996).

    Article  Google Scholar 

  31. Chandler, M. A., Rind, D. & Thompson, R. S. Joint investigations of the middle Pliocene climate II: GISS GCM Northern Hemisphere results. Glob. Planet. Change 9, 197–219 (1994).

    Article  Google Scholar 

  32. Haywood, A. M., Dekens, P., Ravelo, A. C. & Williams, M. Warmer tropics during the mid-Pliocene? Evidence from alkenone paleothermometry and a fully coupled ocean-atmosphere GCM. Geochem. Geophys. Geosyst. 6, Q03010 (2005).

    Article  Google Scholar 

  33. Salzmann, U., Haywood, A. M. & Lunt, D. J. The past is a guide to the future? Comparing Middle Pliocene vegetation with predicted biome distributions for the twenty-first century. Phil. Trans. R. Soc. A 367, 189–204 (2009).

    Article  Google Scholar 

  34. Dowsett, H. J., Robinson, M. M. & Foley, K. M. Pliocene three-dimensional global ocean temperature reconstruction. Clim. Past Discussions 5, 1901–1928 (2009).

    Article  Google Scholar 

  35. Rayner, N. A. et al. Global analyses of sea surface temperature, sea ice, and night marine air temperature since the late nineteenth century. J. Geophys. Res. 108, 4407 (2003).

    Article  Google Scholar 

  36. Peltier, W. R. Global glacial isostasy and the surface of the ice-age Earth: The ICE-5G (VM2) model and GRACE. Annu. Rev. Earth Planet. Sci. 32, 111–149 (2004).

    Article  Google Scholar 

  37. Schellnhuber, H. J., Cramer, W., Nakicenovic, N. & Yohe, G. Avoiding Dangerous Climate Change (Cambridge Univ. Press, 2006).

    Google Scholar 

  38. Meinshausen, M. et al. Greenhouse-gas emission targets for limiting global warming to 2 C. Nature 458, 1158–1162 (2009).

    Article  Google Scholar 

  39. Cox, P. M., Betts, R. A., Jones, C. D., Spall, S. A. & Totterdell, I. J. in Meteorology at the Millennium (ed. Pearce, R.) 259–299 (Academic, 2001).

    Google Scholar 

  40. Alley, R. B., Clark, P. U., Huybrechts, P. & Joughin, I. Ice-sheet and sea-level changes. Science 310, 456–460 (2005).

    Article  Google Scholar 

  41. Zwally, H. J. et al. Surface melt-induced acceleration of Greenland ice-sheet flow. Science 297, 218–222 (2002).

    Article  Google Scholar 

  42. Parizek, B. R. & Alley, R. B. Implications of increased Greenland surface melt under global-warming scenarios: Ice sheet simulations. Quat. Sci. Rev. 23, 1013–1027 (2004).

    Article  Google Scholar 

  43. Lunt, D. J., Haywood, A. M., Foster, G. & Stone, E. J. The Arctic cryosphere in the mid-pliocene and the future. Phil. Trans. R. Soc. A 367, 49–67 (2009).

    Article  Google Scholar 

Download references


This work was carried out in the framework of the British Antarctic Survey (BAS) Greenhouse to ice-house: Evolution of the Antarctic Cryosphere And Palaeoenvironment (GEACEP) programme. D.J.L. is financially supported by BAS and RCUK fellowships.

Author information

Authors and Affiliations



D.J.L. carried out the GCM simulations and analysis. D.J.L., A.M.H., G.A.S. and P.J.V. were involved in the study design. H.J.D. developed the PRISM mid-Pliocene boundary conditions and the PRISM3 SST data set. U.S. carried out the model–data comparison with the vegetation data set. All authors discussed the results and commented on the manuscript.

Corresponding author

Correspondence to Daniel J. Lunt.

Ethics declarations

Competing interests

The authors declare no competing financial interests.

Supplementary information

Supplementary Information

Supplementary Information (PDF 1146 kb)

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Lunt, D., Haywood, A., Schmidt, G. et al. Earth system sensitivity inferred from Pliocene modelling and data. Nature Geosci 3, 60–64 (2010).

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI:

This article is cited by


Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing