Transient Climate Response in a Two-Layer Energy-Balance Model. Part I: Analytical Solution and Parameter Calibration Using CMIP5 AOGCM Experiments

This is the first part of a series of two articles analyzing the global thermal properties of atmosphere‐ocean coupled general circulation models (AOGCMs) within the framework of a two-layer energy-balance model (EBM). In this part, the general analytical solution of the system is given and two idealized climate change scenarios, one with a step forcing and one with a linear forcing, are discussed. These solutions give a didactic description of the contributions from the equilibrium response and of the fast and slow transient responses during a climate transition. Based on these analytical solutions, a simple and physically based procedure to calibratethetwo-layermodelparameters usinganAOGCMstep-forcingexperimentisintroduced.Usingthis procedure, the global thermal properties of 16 AOGCMs participating in phase 5 of the Coupled Model IntercomparisonProject(CMIP5)aredetermined.Itisshownthat,foragivenAOGCM,theEBMtunedwith only the abrupt 43CO2 experiment is able to reproduce with a very good accuracy the temperature evolution in both a step-forcing and a linear-forcing experiment. The role of the upper-ocean and deep-ocean heat uptakes in the fast and slow responses is also discussed. One of the main weaknesses of the simple EBM discussed in this part is its ability to represent the evolution of the top-of-the-atmosphere radiative imbalance in the transient regime. This issue is addressed in Part II by taking into account the efficacy factor of deepocean heat uptake.

[1]  Olivier Geoffroy,et al.  Transient Climate Response in a Two-Layer Energy-Balance Model. Part II: Representation of the Efficacy of Deep-Ocean Heat Uptake and Validation for CMIP5 AOGCMs , 2013 .

[2]  Chandra Sripada,et al.  Reply to Comments , 2013, Perspectives on psychological science : a journal of the Association for Psychological Science.

[3]  J. H. Hateren,et al.  A fractal climate response function can simulate global average temperature trends of the modern era and the past millennium , 2011, 1111.5177.

[4]  G. Peters,et al.  Atmosphere Response Time Scales Estimated from AOGCM Experiments , 2012 .

[5]  K. Taylor,et al.  Forcing, feedbacks and climate sensitivity in CMIP5 coupled atmosphere‐ocean climate models , 2012 .

[6]  Karl E. Taylor,et al.  An overview of CMIP5 and the experiment design , 2012 .

[7]  A. Friend.  Response of Earth's surface temperature to radiative forcing over A.D. 1–2009 , 2011 .

[8]  T. Wigley,et al.  Emulating coupled atmosphere-ocean and carbon cycle models with a simpler model, MAGICC6 - Part 1: Model description and calibration , 2011 .

[9]  Jonathan M. Gregory,et al.  A step‐response simple climate model to reconstruct and interpret AOGCM projections , 2011 .

[10]  T. Delworth,et al.  Probing the Fast and Slow Components of Global Warming by Returning Abruptly to Preindustrial Forcing , 2010 .

[11]  Isaac M. Held,et al.  Importance of Ocean Heat Uptake Efficacy to Transient Climate Change , 2010 .

[12]  Jonathan M. Gregory,et al.  Transient climate response estimated from radiative forcing and observed temperature change , 2008 .

[13]  Jonathan M. Gregory,et al.  Time Variation of Effective Climate Sensitivity in GCMs , 2008 .

[14]  Sandrine Bony,et al.  An Assessment of the Primary Sources of Spread of Global Warming Estimates from Coupled Atmosphere–Ocean Models , 2008 .

[15]  S. Schwartz.  Reply to comments by G. Foster et al., R. Knutti et al., and N. Scafetta on “Heat capacity, time constant, and sensitivity of Earth's climate system” , 2008 .

[16]  Dong L. Wu,et al.  Title : Validation of the Aura Microwave Limb Sounder Temperature and Geopotential Height Measurements , 2007 .

[17]  Julia C. Hargreaves,et al.  Long-term climate commitments projected with climate-carbon cycle models , 2008 .

[18]  M. Webb,et al.  Tropospheric Adjustment Induces a Cloud Component in CO2 Forcing , 2008 .

[19]  M. Budyko.  The Effects of Changing the Solar Constant on the Climate of a General Circulation Model , 2008 .

[20]  S. Schwartz.  Heat capacity, time constant, and sensitivity of Earth's climate system , 2007 .

[21]  B. Soden,et al.  An Assessment of Climate Feedbacks in Coupled Ocean–Atmosphere Models , 2006 .

[22]  J. Hansen,et al.  Efficacy of climate forcings , 2005 .

[23]  Jonathan M. Gregory,et al.  A new method for diagnosing radiative forcing and climate sensitivity , 2004 .

[24]  Jonathan M. Gregory,et al.  The Role of Climate Sensitivity and Ocean Heat Uptake on AOGCM Transient Temperature Response , 2002 .

[25]  J. Gregory.  Vertical heat transports in the ocean and their effect on time-dependent climate change , 2000 .

[26]  Jonathan M. Gregory,et al.  The climate response to CO2 of the Hadley Centre coupled AOGCM with and without flux adjustment , 1997 .

[27]  J. Murphy.  Transient Response of the Hadley Centre Coupled Ocean-Atmosphere Model to Increasing Carbon Dioxide. Part III: Analysis of Global-Mean Response Using Simple Models , 1995 .

[28]  Robert Sausen,et al.  On the cold start problem in transient simulations with coupled atmosphere-ocean models , 1992 .

[29]  D. Hofmann,et al.  Reply to comments , 1990 .

[30]  J. Houghton,et al.  Climate change : the IPCC scientific assessment , 1990 .

[31]  R. Dickinson.  Convergence Rate and Stability of Ocean-Atmosphere Coupling Schemes with a Zero-Dimensional Climate Model , 1981 .

[32]  William D. Sellers,et al.  A Global Climatic Model Based on the Energy Balance of the Earth-Atmosphere System. , 1969 .