Climate Dynamics

, Volume 22, Issue 8, pp 823–838 | Cite as

Simple indices of global climate variability and change Part II: attribution of climate change during the twentieth century

  • K. BraganzaEmail author
  • D. J. Karoly
  • A. C. Hirst
  • P. Stott
  • R. J. Stouffer
  • S. F. B. Tett


Five simple indices of surface temperature are used to investigate the influence of anthropogenic and natural (solar irradiance and volcanic aerosol) forcing on observed climate change during the twentieth century. These indices are based on spatial fingerprints of climate change and include the global-mean surface temperature, the land-ocean temperature contrast, the magnitude of the annual cycle in surface temperature over land, the Northern Hemisphere meridional temperature gradient and the hemispheric temperature contrast. The indices contain information independent of variations in global-mean temperature for unforced climate variations and hence, considered collectively, they are more useful in an attribution study than global mean surface temperature alone. Observed linear trends over 1950–1999 in all the indices except the hemispheric temperature contrast are significantly larger than simulated changes due to internal variability or natural (solar and volcanic aerosol) forcings and are consistent with simulated changes due to anthropogenic (greenhouse gas and sulfate aerosol) forcing. The combined, relative influence of these different forcings on observed trends during the twentieth century is investigated using linear regression of the observed and simulated responses of the indices. It is found that anthropogenic forcing accounts for almost all of the observed changes in surface temperature during 1946–1995. We found that early twentieth century changes (1896–1945) in global mean temperature can be explained by a combination of anthropogenic and natural forcing, as well as internal climate variability. Estimates of ‘scaling factors’ that weight the amplitude of model simulated signals to corresponding observed changes using a combined normalized index are similar to those calculated using more complex, optimal fingerprint techniques.


Forced Response Sulfate Aerosol Meridional Temperature Gradient Volcanic Aerosol Internal Climate Variability 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.



This study was stimulated by our involvement in the preparation of the IPCC Third Assessment Report. We are grateful to Phil Jones for providing access to the observational data and to the IPCC Data Distribution Centre for providing access to additional climate model data, particularly the ECHAM4 data. Much of this research was carried out by Karl Braganza while he was supported by a graduate scholarship from the CRC for Southern Hemisphere Meteorology at Monash University. It has been completed while he has been funded as a research fellow through an ARC Discovery Grant at Monash University. Peter Stott and computer time for the HadCM2 and HadCM3 simulations was funded by the UK Department of Environment, Food and Rural Affairs under contract PECD 7/12/37. Simon Tett was funded by the UK GMR program.


  1. Allen MR, Tett SFB (1999) Checking for model consistency in optimal fingerprinting. Clim Dyn 15: 419–434CrossRefGoogle Scholar
  2. Allen MR, Stott PA, Mitchell JFB, Schnur R, Delworth TL (2000) Quantifying the uncertainty in forecasts of anthropogenic climate change. Nature 407: 617–620PubMedGoogle Scholar
  3. Braganza K, Karoly DJ, Hirst AC, Mann ME, Stott P, Stouffer J, Tett, SFB (2003) Simple indices of global climate variability and change: Part I, variability and correlation structure. Clim Dyn 20: 491–502Google Scholar
  4. Collins M, Tett SFB, Cooper C (2001) The internal climate variability of HadCM3, a version of the Hadley Centre coupled model without flux adjustments. Clim Dyn 17: 61–81CrossRefGoogle Scholar
  5. Crowley TJ (2000) Causes of climate change over the past 1000 years. Science 289 270–277Google Scholar
  6. Crowley TJ, Kim K-Y (1999) Modelling the temperature response to forced climate change over the last six centuries. Geophys Res Lett 26: 1901–1904CrossRefGoogle Scholar
  7. Cusack S, Slingo A, Edwards JM, Wild M (1998) The radiative impact of a simple aerosol climatology on the Hadley Centre GCM. QJR Meteorol Soc 124: 2517–2526CrossRefGoogle Scholar
  8. Delworth TL, Stouffer RJ, Dixon KW, Spelman MJ, Knutson TR, Broccoli AJ, Kushner PJ, Wetherald RT (2002) Review of simulations of climate variability and change with the GFDL R30 coupled climate model. Clim Dyn 19: 555–574CrossRefGoogle Scholar
  9. Dixon KW, Delworth Tl, Knutson TR, Spelman MJ, Stouffer RJ (2003) A Comparison of climate change simulations produced by two CFDL Coupled climate models. Global Planet change 37: 81–102CrossRefGoogle Scholar
  10. Edwards JM, Slingo A (1996) Studies with a flexible new radiation code. I: choosing a configuration for a large scale model. QJR Meteorol Soc 122: 689–719CrossRefGoogle Scholar
  11. Folland CK, Karl TR, Christy JR, Clarke RA, Gruza GV, Jouzel J, Mann ME, Oerlemans J, Salinger MJ, Wang S-W (2001) Observed climate variability and change. In Houghton, JT, Ding Y,Griggs DJ, Noguer M, van der Linden PJ, Dai X, Maskell K, Johnson CA (eds) Climate change 2001: The scientific basis, Contribution of Working Group 1 to the Third Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press, Cambridge, UK, pp 99–182Google Scholar
  12. Free M, Robock A (1999) Global warming in the context of the Little Ice Age. J Geophys Res 104: 19,057–19,070CrossRefGoogle Scholar
  13. Gitelman AI, Risbey JR, Kass RE, Rosen RD (1997) Trends in the surface meridional temperature gradient. Geophys Res Lett 24: 1243–1246CrossRefGoogle Scholar
  14. Gitelman AI, Risbey JR, Kass RE, Rosen RD (1999) Sensitivity of a meridional temperature gradient index to latitudinal domain. J Geophys Res 104: 16,709–16,717CrossRefGoogle Scholar
  15. Graf H-F, Kirchner I, Schult I (1996) Modelling Mt. Pinatubo climate effects. NATO-ASI Series, vol 142, In: Fiocco G, Dua D (eds) The Mount Pinatubo Eruption, Springer, Berlin Heidelberg New York, pp 219–231Google Scholar
  16. Gordon HB, O’Farrell SP (1997) Transient climate change in the CSIRO coupled model with dynamic sea-ice. Mon Weather Rev 125: 875–907CrossRefGoogle Scholar
  17. Gordon C, Cooper C, Senior CA, Banks HT, Gregory JM, Johns TC, Mitchell JFB, Wood RA (2000) The simulation of SST, sea ice extents and ocean heat transports in a version of the Hadley Centre coupled model without flux adjustments. Clim Dyn 16: 147–168CrossRefGoogle Scholar
  18. Hasselmann K (1993) Optimal fingerprints for the detection of time dependent climate change. J Clim 6: 1957–1971CrossRefGoogle Scholar
  19. Hegerl GC, Hasselmann K, Cubasch U, Mitchell JFB, Roeckner E, Voss R, Waszkewitz J (1997) Multi-fingerprint detection and attribution of greenhouse gas- and aerosol forced climate change. Clim Dyn 13: 613–634CrossRefGoogle Scholar
  20. Hirst AC (1999) The Southern Ocean response to global warming in the CSIRO coupled ocean-atmosphere model. Environ. Model Software: Spec Iss Modelling Global Climatic Change. 14: 227–242Google Scholar
  21. Hirst AC, O’Farrell SP, Gordon HB, (2000) Comparison of a coupled ocean-atmosphere model with and without oceanic eddy-induced advection. 1. Ocean spin-up and control integrations. J Clim 13: 139–163CrossRefGoogle Scholar
  22. Hoyt DV, Schatten KH (1993) A discussion of plausible solar irradiance variations, 1700–1992. J Geophys Res 98: 18,895-18,905Google Scholar
  23. Jain S, Lall U, Mann ME (1999) Seasonality and interannual variations of Northern Hemisphere temperature: equator to pole temperature gradient and land-ocean contrast. J Clim 12: 1086–1100CrossRefGoogle Scholar
  24. Johns TC (1996) A description of the Second Hadley Centre Coupled Model (HadCM2). Climate Research Technical Note 71, Hadley Centre, United Kingdom Meteorological Office, Bracknell Berkshire RG12 2SY, United Kingdom, pp 19Google Scholar
  25. Johns TC, Carnell RE, Crossley JF, Gregory JM, Mitchell JFB, Senior CA, Tett SFB, Wood RA (1997) The second Hadley Centre coupled ocean-atmosphere GCM: model description, spin-up and validation. Clim Dyn 13: 103–134CrossRefGoogle Scholar
  26. Johns TC, Gregory JM, Stott PA, Mitchell JFB (2001) Correlations between patterns of 19th and 20th century surface temperature change and HadCM2 climate model ensembles. Geophys Res Lett 28: 1007–1010CrossRefGoogle Scholar
  27. Johns TC, Gregory JM, Ingram WJ, Johnson CE, Jones A, Lowe JA, Mitchell JFB, Roberts DL, Sexton DMH, Stevenson DS, Tett SFB, Woodage MJ (2003) Anthropogenic climate change for 1860 to 2100 simulated with HadCM3 model under updated emissions scenarios. Clim Dyn 20: 583–612Google Scholar
  28. Jones PD (1995) Land surface temperatures- Is the network good enough? Clim Change 31: 545–558Google Scholar
  29. Jones PD, New M, Parker DE, Martin S, Rigor IG (1999) Surface air temperature and its changes over the past 150 years. Rev Geophysics 37: 173–199CrossRefGoogle Scholar
  30. Karoly DJ, Braganza K (2001) Identifying global climate change using simple indices. Geophys Res Lett 28: 2205–2208CrossRefGoogle Scholar
  31. Kaufmann RK, Stern DI (1997) Evidence for human influence on climate from hemispheric temperature relations. Nature 388: 39–44Google Scholar
  32. Kirchner I, Stenchikov GL, Graf H-F, Robock A, Antuna JC (1999) Climate model simulation of winter warming and summer cooling following the 1991 Mount Pinatubo volcanic eruption. J Geophys Res 104: 19,039–19,055CrossRefGoogle Scholar
  33. Lean J, Beer J, Bradley R (1995) Reconstruction of solar irradiance since 1610: Implications for climate change. Geophys Res Lett 22: 3195–3198CrossRefGoogle Scholar
  34. Manabe S, Stouffer RJ (1980) Sensitivity of a global climate model to an increase in the CO2 concentration in the atmosphere. J Geophys Res 85: 5529–5554Google Scholar
  35. Mann ME, Park J (1996) Greenhouse warming and changes in the seasonal cycle of temperature: Model versus observations. Geophys Res Lett 23: 1111–1114Google Scholar
  36. Mao J, Robock A (1998) Surface air temperature simulations by AMIP general circulation models: volcanic and ENSO signals and systematic errors. J Clim 11: 1538–1552CrossRefGoogle Scholar
  37. McAvaney BJ, Covey C, Joussaume S, Kattsov V, Kitoh A, Ogana W, Pitman AJ, Weaver AJ, Wood RA, Zhao Z-C (2001) Model evaluation. In: Houghton JT, Ding Y, Griggs DJ, Noguer M, van der Linden PJ, Dai X, Maskell K, Johnson CA (eds) Climate change 2001: the scientific basis. Contribution of Working Group 1 to the Third Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press, Cambridge, UK, pp. 471–524Google Scholar
  38. Meehl GA, Washington WM, Karl TM (1993) Low-frequency variability and CO2 tanist climate change: Part 1. Time-averaged differences. Clim Dyn 8: 117–133Google Scholar
  39. Mitchell JFB, Karoly DJ, Allen MR, Hegerl G, Zwiers F, Marengo J (2001) Detection of climate change and attribution of causes. In: Houghton JT et al. (eds) Climate change 2001: the scientific basis. Contribution of Working Group I to the Third Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press, Cambridge, UK, pp 695–738Google Scholar
  40. Myers RH (1986) Classical and modern regression with applications. 2nd Edn. Duxbury Press, Belmont, Calfornia, pp 486Google Scholar
  41. Oberhuber JM (1993) The OPYC ocean general circulation model. Techn Rep 7, Deutsches Klimarechenzentrum, Hamburg, GermanyGoogle Scholar
  42. Parker DE, Folland CK, Jackson M (1995) Marine surface temperature: Observed variations and data requirements. Clim Change 31: 559–600Google Scholar
  43. Robock A (2000) Volcanic eruptions and climate. Rev Geophys 38: 191–219CrossRefGoogle Scholar
  44. Robock A, Free M (1995) Ice cores an index of global volcanism from 1850 to the present. J Geophys Res 100: 11,567–11,576CrossRefGoogle Scholar
  45. Roeckner E, Arpe K, Bengtsson L, Christoph M, Claussen M, Dümenil L, Esch M, Giorgetta M, Schlese U, Schulzweida U (1996a) The atmospheric general circulation model ECHAM4: Model description and simulation of present-day climate. MPI Report 218, Max-Planck-Institut für Meteorologie, Hamburg, Germany, pp 90Google Scholar
  46. Roeckner E, Oberhuber JM, Bacher A, Christoph M, Kirchner I (1996b) ENSO variability and atmospheric response in a global coupled atmosphere-ocean GCM. Clim Dyn 12: 737–754CrossRefGoogle Scholar
  47. Santer BD, Wigley TML, Jones PD (1993) Correlation methods in fingerprint detection studies. Clim Dyn 8: 265–276Google Scholar
  48. Santer BD, Taylor KE, Wigley TML, Johns TC, Jones PD, Karoly DJ, Mitchell JFB, Oort AH, Penner JE, Ramaswamy V, Schwarzkopf MD, Stouffer RJ, Tett SFB (1996) A search for human influences on the thermal structure in the atmosphere. Nature 382: 39–46Google Scholar
  49. Sato M, Hansen JE, McCormick MP, Pollack J (1993) Stratospheric aerosol optical depths (1850–1990). J Geophys Res 98: 22,987–22,994Google Scholar
  50. Shine KP, Forster PM (1999) The effects of human activity on radiative forcing of climate change: a review of recent developments. Global Planet Change 20: 205–225CrossRefGoogle Scholar
  51. Stott PA, Tett SFB (1998) Scale-dependent detection of climate change. J Clim 11: 3282–3294CrossRefGoogle Scholar
  52. Stott PA, Allen MR, Jones GS (2000a) Estimating signal amplitudes in optimal fingerprinting II: application to general circulation models. Hadley Centre Tech Note 20, Hadley Centre for Climate Prediction and Response, Meteorological Office, RG12 2SY UKGoogle Scholar
  53. Stott PA, Tett SFB, Jones GS, Allen MR, Mitchell JFB, Jenkins GJ (2000b) External control of twentieth century temperature by natural and anthropogenic forcings. Science 290: 2133–2137PubMedGoogle Scholar
  54. Stott PA, Tett SFB, Jones GS, Allen MR, Ingram WJ, Mitchell JFB (2001) Attribution of twentieth century temperature change to natural and anthropogenic Causes. Clim Dyn 17: 1–22Google Scholar
  55. Tett SFB, Stott PA, Allen MR, Ingram WJ, Mitchell JFB (1999) Causes of twentieth century temperature change near the Earth’s surface. Nature 399: 569–572Google Scholar
  56. Tett SFB, Jones GS, Stott PA, Hill DC, Mitchell JFB, Allen MR, Ingram WJ, Johns TC, Johnson CE, Jones A, Roberts DL, Sexton DMH, Woodage MJ (2002) Estimation of natural and anthropogenic contributions to 20th century temperature change. J Geophys Res 107:doi 10.1029/2000JD000028CrossRefGoogle Scholar
  57. Thomson DJ (1995) The seasons, global temperature, precession and CO2 Science 268: 59–68Google Scholar
  58. Wigley TML, Barnett TP (1990) Detection of the greenhouse effect in the observations. In: Houghton JT, Jenkins GJ, Ephraums JJ (eds) Climate Change: The IPCC Scientific Assessment. Cambridge University Press, Cambridge, UK, pp 239–256Google Scholar
  59. Wigley TML, Smith RL, Santer BD (1998) Anthropogenic influence on the autocorrelation structure of hemispheric-mean temperatures. Science 282: 1676–1679PubMedGoogle Scholar

Copyright information

© Springer-Verlag  2004

Authors and Affiliations

  • K. Braganza
    • 1
    Email author
  • D. J. Karoly
    • 1
    • 5
  • A. C. Hirst
    • 2
  • P. Stott
    • 3
  • R. J. Stouffer
    • 4
  • S. F. B. Tett
    • 3
  1. 1.School of Mathematics SciencesMonash UniversityClaytonAustralia
  2. 2.CSIRO Atmospheric ResearchAspendaleAustralia
  3. 3.Hadley Center for Climate Prediction and ResearchMeteorological OfficeBracknellUK
  4. 4.Geophysical Fluid Dynamics LaboratoryPrincetonUSA
  5. 5.School of MeteorologyUniversity of OklahomaNormanUSA

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