Editorial Type:
Article
Article Type:
Research Article

Interpretation of Simulated Global Warming Using a Simple Model

I. G. Watterson CSIRO Atmospheric Research, Aspendale, Victoria, Australia

Search for other papers by I. G. Watterson in
Current site
Google Scholar
PubMed Close
Print Publication:
01 Jan 2000
DOI:
https://doi.org/10.1175/1520-0442(2000)013<0202:IOSGWU>2.0.CO;2
Page(s):
202–215
Restricted access

Abstract

A simple energy balance model with two parameters, an effective heat capacity and an effective climate sensitivity, is used to interpret six GCM simulations of greenhouse gas–induced global warming. By allowing the parameters to vary in time, the model can be accurately calibrated for each run. It is found that the sensitivity can be approximated as a constant in each case. However, the effective heat capacity clearly varies, and it is important that the energy equation is formulated appropriately, and thus unlike many such models. For simulations with linear forcing and from a cold start, the capacity is in each case close to that of a homogeneous ocean with depth initially 200 m, but increasing some 4.3 m each year, irrespective of the sensitivity and forcing growth rate. Analytic solutions for this linear capacity function are derived, and these reproduce the GCM runs well, even for cases where the forcing is stabilized after a century or so. The formation of a subsurface maximum in the mean ocean temperature anomaly is a significant feature of such cases. A simple model for a GCM run with a realistic forcing scenario starting from 1880 is constructed using component results for forcing segments. Given this, an estimate of the cold start error of a simulation of the warming due to forcing after the present would be given by the negative of the temperature drift of the anomaly due to the past forcing. The simple model can evidently be used to give an indication of likely warming curves, at least for this range of scenarios and GCM sensitivities.

Corresponding author address: Dr. Ian G. Watterson, CSIRO Atmospheric Research, 107-121 Station Street, PMB1, Aspendale, Victoria 3195, Australia.

Email: igw@dar.csiro.au

Abstract

A simple energy balance model with two parameters, an effective heat capacity and an effective climate sensitivity, is used to interpret six GCM simulations of greenhouse gas–induced global warming. By allowing the parameters to vary in time, the model can be accurately calibrated for each run. It is found that the sensitivity can be approximated as a constant in each case. However, the effective heat capacity clearly varies, and it is important that the energy equation is formulated appropriately, and thus unlike many such models. For simulations with linear forcing and from a cold start, the capacity is in each case close to that of a homogeneous ocean with depth initially 200 m, but increasing some 4.3 m each year, irrespective of the sensitivity and forcing growth rate. Analytic solutions for this linear capacity function are derived, and these reproduce the GCM runs well, even for cases where the forcing is stabilized after a century or so. The formation of a subsurface maximum in the mean ocean temperature anomaly is a significant feature of such cases. A simple model for a GCM run with a realistic forcing scenario starting from 1880 is constructed using component results for forcing segments. Given this, an estimate of the cold start error of a simulation of the warming due to forcing after the present would be given by the negative of the temperature drift of the anomaly due to the past forcing. The simple model can evidently be used to give an indication of likely warming curves, at least for this range of scenarios and GCM sensitivities.

Corresponding author address: Dr. Ian G. Watterson, CSIRO Atmospheric Research, 107-121 Station Street, PMB1, Aspendale, Victoria 3195, Australia.

Email: igw@dar.csiro.au

Save
Cover Journal of Climate
Journal of Climate

  • Bryan, K., 1969: A numerical method for the study of the circulation of the world ocean. J. Comput. Phys.,4, 347–376.

  • Cai, W., and H. B. Gordon, 1998: Transient responses of the CSIRO climate model to two different rates of CO2 increase. Climate Dyn.,14, 503–516.

  • Colman, R. A., and B. J. McAvaney, 1995: Sensitivity of the climate response of an atmospheric general circulation model to changes in convective parameterization and horizontal resolution. J. Geophys. Res.,100, 3155–3172.

  • ——, S. B. Power, B. J. McAvaney, and R. R. Dahni, 1995: A non-flux-corrected transient CO2 experiment using the BMRC coupled atmosphere/ocean GCM. Geophys. Res. Lett.,22, 3047–3050.

  • Dickinson, R. E., and K. J. Schaudt, 1998: Analysis of timescales of response of a simple climate model. J. Climate,11, 97–107.

  • Dix, M. R., and B. G. Hunt, 1998: Transient climatic change to 3×CO2. Global Planet. Change,18, 15–36.

  • Dutton, J. A., 1995: An analytical model of atmospheric feedback and global temperature change. J. Climate,8, 1122–1139.

  • Gates, W. L., and Coauthors, 1996: Climate models—Evaluation. Climate Change 1995: The Science of Climate Change, J. T. Houghton et al., Eds., Cambridge University, Press, 229–284.

  • Gent, P. R., and J. C. McWilliams, 1990: Isopycnal mixing in ocean circulation models. J. Phys. Oceanogr.,20, 150–155.

  • Gordon, H. B., and S. P. O’Farrell, 1997: Transient climate change in the CSIRO coupled model with dynamic sea ice. Mon. Wea. Rev.,125, 875–907.

  • Gregory, J. M., and J. F. B. Mitchell, 1997: The climate response to CO2 of the Hadley Centre coupled AOGCM with and without flux adjustment. Geophys. Res. Lett.,24, 1943–1946.

  • Hasselmann, K., R. Sausen, E. Maier-Reimer, and R. Voss, 1993: On the cold start problem in transient simulations with coupled ocean–atmosphere models. Climate Dyn.,9, 53–61.

  • Hirst, A. C., 1999: The Southern Ocean response to global warming in the CSIRO coupled ocean-atmosphere model. Environ. Model. Software,14,227–241.

  • ——, H. B. Gordon, and S. P. O’Farrell, 1996: Response of a coupled ocean-atmosphere model including oceanic eddy-induced advection to anthropogenic CO2 increase. Geophys. Res. Lett.,23, 3361–3364.

  • Hoffert, M. I., A. J. Callegari, and C.-T. Hsieh, 1980: The role of deep sea heat storage in the secular response to climatic forcing. J. Geophys. Res.,85, 6667–6679.

  • Kattenburg, A., and Coauthors, 1996: Climate models—Projections of future climate. Climate Change 1995: The Science of Climate Change, J. T. Houghton et al., Eds., Cambridge University Press, 285–357.

  • Keen, A. B., and J. M. Murphy, 1997: Influence of natural variability and the cold start on the simulated transient response to increasing CO2. Climate Dyn.,13, 847–864.

  • Leggett, J., W. J. Pepper, and R. J. Swart, 1992: Emission scenarios for the IPCC: An update. Climate Change 1992: The Supplementary Report to the IPCC Scientific Assessment, J. T. Houghton et al., Eds., Cambridge University Press, 69–95.

  • Manabe, S., and R. J. Stouffer, 1994: Multiple-century response of a coupled ocean–atmosphere model to an increase of atmospheric carbon dioxide. J. Climate,7, 5–23.

  • ——, R. J. Stouffer, M. J. Spelman, and K. Bryan, 1991: Transient responses of a global ocean–atmosphere model to gradual changes of atmospheric CO2. Part I: Annual mean response. J. Climate,4, 785–818.

  • Mitchell, J. F. B., and T. C. Johns, 1997: On modification of global warming by sulfate aerosols. J. Climate,10, 245–267.

  • Murphy, J. M., 1995: Transient response of the Hadley Centre coupled ocean–atmosphere model to increasing carbon dioxide. Part III:Analysis of global-mean response using simple models. J. Climate,8, 496–514.

  • Schlesinger, M. E., 1989: Model projections of the climatic changes by increased atmospheric CO2. Climate and Geo-Sciences, A. Berger et al., Eds., Kluwer Academic, 375–415.

  • Schneider, E. K., 1996: Flux correction and the simulation of changing climate. Ann. Geophys.,14, 336–341.

  • Watterson, I. G., 1997: Predictions of global warming using a simple energy balance model. Symposium on Climate Prediction and Predictability, J. D. Jasper and P. J. Meighen, Eds., Bureau of Meteorology, 105–109.

  • ——, S. P. O’Farrell, and M. R. Dix, 1997: Energy and water transport in climates simulated by a general circulation model that includes dynamic sea ice. J. Geophys. Res.,102, 11 027–11 037.

  • ——, M. R. Dix, and R. Colman, 1999: A comparison of present and doubled CO2 climates and feedbacks simulated by three general circulation models. J. Geophys. Res.,104, 1943–1956.

  • Wigley, T. M. L., 1987: Relative contributions of different trace gases to the greenhouse effect. Climate Monitor,16, 14–29.

  • ——, and S. C. B. Raper, 1992: Implications for climate and sea level of revised IPCC emissions scenarios. Nature,357, 293–300.

All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 568 159 6
PDF Downloads 276 55 4