Modeling climatic effects of anthropogenic carbon dioxide emissions: unknowns and uncertainties

A likelihood of disastrous global environmental consequences has been surmised as a result of projected increases in anthropogenic greenhouse gas emissions. These estimates are based on computer climate modeling, a branch of science still in its infancy despite recent substantial strides in knowledge. Because the expected anthropogenic climate forcings are relatively small compared to other background and forcing factors (internal and external), the credibility of the modeled global and regional responses rests on the validity of the models. We focus on this important question of climate model validation. Specifically, we review common deficiencies in general circulation model (GCM) calculations of atmospheric temperature, surface temperature, precipitation and their spatial and tem- poral variability. These deficiencies arise from complex problems associated with parameterization of multiply interacting climate components, forcings and feedbacks, involving especially clouds and oceans. We also review examples of expected climatic impacts from anthropogenic CO2 forcing. Given the host of uncertainties and unknowns in the difficult but important task of climate modeling, the unique attribution of observed current climate change to increased atmospheric CO2 concentration, including the relatively well-observed latest 20 yr, is not possible. We further conclude that the incau- tious use of GCMs to make future climate projections from incomplete or unknown forcing scenarios is antithetical to the intrinsically heuristic value of models. Such uncritical application of climate models has led to the commonly held but erroneous impression that modeling has proven or substantiated the hypothesis that CO2 added to the air has caused or will cause significant global warming. An assess- ment of the merits of GCMs and their use in suggesting a discernible human influence on global cli- mate can be found in the joint World Meteorological Organisation and United Nations Environmental Programme's Intergovernmental Panel on Climate Change (IPCC) reports (1990, 1995 and the up- coming 2001 report). Our review highlights only the enormous scientific difficulties facing the calcu- lation of climatic effects of added atmospheric CO2 in a GCM. The purpose of such a limited review of the deficiencies of climate model physics and the use of GCMs is to illuminate areas for improvement. Our review does not disprove a significant anthropogenic influence on global climate.

[1]  S. Schneider,et al.  Climate stabilization: for better or for worse? , 1974, Science.

[2]  G. Shutts,et al.  Mechanisms and models of climatic change , 1978, Nature.

[3]  M. Lighthill.  The recently recognized failure of predictability in Newtonian dynamics , 1986, Proceedings of the Royal Society of London. A. Mathematical and Physical Sciences.

[4]  Amartya Sen,et al.  Prediction and economic theory , 1986, Proceedings of the Royal Society of London. A. Mathematical and Physical Sciences.

[5]  Richard C. J. Somerville,et al.  The predictability of weather and climate , 1987 .

[6]  Wallace S. Broecker,et al.  Unpleasant surprises in the greenhouse? , 1987, Nature.

[7]  C. Schuurmans,et al.  The correlation of tropospheric and stratospheric temperatures and its effect on the detection of climate changes , 1990 .

[8]  P. Rasch,et al.  Computational aspects of moisture transport in global models of the atmosphere , 1990 .

[9]  C. Essex.  What do climate models tell us about global warming? , 1991 .

[10]  Syukuro Manabe,et al.  Century-scale effects of increased atmospheric C02 on the ocean–atmosphere system , 1993, Nature.

[11]  Stephen H. Schneider,et al.  Detecting Climatic Change Signals: Are There Any "Fingerprints"? , 1994, Science.

[12]  N Oreskes,et al.  Verification, Validation, and Confirmation of Numerical Models in the Earth Sciences , 1994, Science.

[13]  J. Murphy,et al.  Transient response of the Hadley Centre coupled ocean-atmosphere model to increasing carbon-dioxide , 1995 .

[14]  J. Wallace,et al.  Dynamic Contribution to Hemispheric Mean Temperature Trends , 1995, Science.

[15]  L. Ferranti,et al.  Northern Hemisphere atmospheric blocking as simulated by 15 atmospheric general circulation models in the period 1979–1988 , 1998 .

[16]  Gary E. Thomas,et al.  Is the polar mesosphere the miner's canary of global change? , 1996 .

[17]  S. Schneider,et al.  Geoengineering: Could— or should— we do it? , 1996 .

[18]  K. Trenberth,et al.  Earth's annual global mean energy budget , 1997 .

[19]  Donald R. Johnson.  “General Coldness of Climate Models” and the Second Law: Implications for Modeling the Earth System , 1997 .

[20]  R. Lindzen.  Can increasing carbon dioxide cause climate change? , 1997, Proceedings of the National Academy of Sciences of the United States of America.

[21]  Roger Temam,et al.  Physical Interpretation of the Attractor Dimension for the Primitive Equations of Atmospheric Circulation , 1997 .

[22]  B. Weare,et al.  Uncertainties in Global Ocean Surface Heat Flux Climatologies Derived from Ship Observations , 1995 .

[23]  N. Lau,et al.  The Cold Ocean-Warm Land Pattern: Model Simulation and Relevance to Climate Change Detection , 1998 .

[24]  S. Idso.  CO2-induced global warming: a skeptic\'s view of potential climate change , 1998 .

[25]  M. Gadsden,et al.  The North-West Europe data on noctilucent clouds: a survey fn2 fn2 This paper was presented in the p , 1998 .

[26]  David G. Victor,et al.  Strategies for cutting carbon , 1998, Nature.

[27]  Gerald R. North,et al.  Testing climate models : An approach , 1998 .

[28]  Michael Ghil,et al.  Seasonal and interannual variations of atmospheric CO2 and climate , 1998 .

[29]  Anthony D. Del Genio,et al.  Effects of Cloud Parameterization on the Simulation of Climate Changes in the GISS GCM , 1999 .

[30]  G. Russell,et al.  Response to CO2 transient increase in the GISS coupled model : Regional coolings in a warming climate , 1999 .

[31]  W. Arthur,et al.  Complexity and the economy , 2014, Science.

[32]  F. Joos,et al.  The variability in the carbon sinks as reconstructed for the last 1000 years , 1999 .

[33]  S. Rahmstorf.  Shifting seas in the greenhouse? , 1999, Nature.

[34]  Jonathan M. Gregory,et al.  Changing spatial structure of the thermohaline circulation in response to atmospheric CO2 forcing in a climate model , 1999, Nature.

[35]  A Discussion on the Errors in the Surface Heat Fluxes Simulated by a Coupled GCM , 1999 .

[36]  W. Tucker.  The Lorenz attractor exists , 1999 .

[37]  Ramaswamy,et al.  Tropospheric Aerosol Climate Forcing in Clear-Sky Satellite Observations over the Oceans. , 1999, Science.

[38]  Lennart Bengtsson,et al.  Why is the global warming proceeding much slower than expected , 1999 .

[39]  Axel Timmermann,et al.  Detecting the Nonstationary Response of ENSO to Greenhouse Warming , 1999 .

[40]  Tim Palmer,et al.  A Nonlinear Dynamical Perspective on Climate Prediction , 1999 .

[41]  J. Räisänen.  Internal Variability as a Cause of Qualitative Intermodel Disagreement on Anthropogenic Climate Changes , 1999 .

[42]  Stefan Rahmstorf,et al.  Long-Term Global Warming Scenarios Computed with an Efficient Coupled Climate Model , 1999 .

[43]  H. Dijkstra,et al.  Imperfections of the Thermohaline Circulation: Multiple Equilibria and Flux Correction* , 1999 .

[44]  L. Rotstayn.  Climate Sensitivity of the CSIRO GCM: Effect of Cloud Modeling Assumptions , 1999 .

[45]  Ian G. Enting,et al.  Reconstructing the recent carbon cycle from atmospheric CO2, δ13C and O2/N2 observations* , 1999 .

[46]  W. Cai,et al.  Southern High-Latitude Ocean Climate Drift in a Coupled Model. , 1999 .

[47]  Lennart Bengtsson,et al.  Transient Climate Change Simulations with a Coupled Atmosphere–Ocean GCM Including the Tropospheric Sulfur Cycle , 1999 .

[48]  Thomas F. Stocker,et al.  The Stability of the Thermohaline Circulation in Global Warming Experiments , 1999 .

[49]  C. Senior.  Comparison of Mechanisms of Cloud-Climate Feedbacks in GCMs , 1999 .

[50]  Christopher B. Field,et al.  The Not-So-Big U.S. Carbon Sink , 1999, Science.

[51]  Benjamin Kirtman,et al.  Tropospheric Water Vapor and Climate Sensitivity , 1999 .

[52]  S. Manabe,et al.  Response of a Coupled Ocean–Atmosphere Model to Increasing Atmospheric Carbon Dioxide: Sensitivity to the Rate of Increase , 1999 .

[53]  Michael A. Arthur,et al.  Miocene evolution of atmospheric carbon dioxide , 1999 .

[54]  J. Kutzbach,et al.  Modeling long-term climate changes with equilibrium asynchronous coupling , 1999 .

[55]  R. Stouffer,et al.  The influence of transient surface fluxes on North Atlantic overturning in a coupled GCM Climate Change Experiment , 1999 .

[56]  Upmanu Lall,et al.  Seasonality and Interannual Variations of Northern Hemisphere Temperature: Equator-to-Pole Gradient and Ocean–Land Contrast , 1999 .

[57]  Smith,et al.  Ice core records of atmospheric CO2 around the last three glacial terminations , 1999, Science.

[58]  How Far have we Come in Understanding the Dynamics of the Middle Atmosphere , 1999 .

[59]  Willie Soon,et al.  Environmental Effects of Increased Atmospheric Carbon Dioxide , 1999 .

[60]  Joseph Egger.  Numerical Generation of Entropies , 1999 .

[61]  Martin Wahlen,et al.  Holocene carbon-cycle dynamics based on CO2 trapped in ice at Taylor Dome, Antarctica , 1999, Nature.

[62]  K. Kodera,et al.  Northern hemisphere winter circulation associated with the North Atlantic Oscillation and stratospheric polar‐night jet , 1999 .

[63]  Tim N. Palmer,et al.  Signature of recent climate change in frequencies of natural atmospheric circulation regimes , 1999, Nature.

[64]  B. Soden.  The Sensitivity of the Tropical Hydrological Cycle to ENSO , 2000 .

[65]  David Rind,et al.  Comparison of Model and Observed Regional Temperature Changes During the Past 40 Years , 2000 .

[66]  R. Oglesby,et al.  The relationship between atmospheric water vapor and temperature in simulations of climate change , 2000 .

[67]  Behl,et al.  Carbon isotopic evidence for methane hydrate instability during quaternary interstadials , 2000, Science.

[68]  Matthew D. Collins,et al.  Understanding uncertainties in the response of ENSO to greenhouse warming , 2000 .

[69]  Ocean-atmosphere interactions and climate drift in a coupled general circulation model , 2000 .

[70]  R. Alley.  Ice-core evidence of abrupt climate changes. , 2000, Proceedings of the National Academy of Sciences of the United States of America.

[71]  L. Sloan,et al.  Comparison of temperature variability in observations and sixteen climate model simulations , 2000 .

[72]  G. Meehl,et al.  The seasonal cycle in coupled ocean-atmosphere general circulation models , 2000 .

[73]  Ken Caldeira,et al.  Geoengineering Earth's radiation balance to mitigate CO2‐induced climate change , 2000 .

[74]  E. Clothiaux,et al.  Cloud Droplet Size Distributions in Low-Level Stratiform Clouds , 2000 .

[75]  A. Genio,et al.  The Temperature Dependence of the Liquid Water Path of Low Clouds in the Southern Great Plains , 2000 .

[76]  Andrei P. Sokolov,et al.  Constraining uncertainties in climate models using climate change detection techniques , 2000 .

[77]  Mingxing Wang,et al.  Monsoon ecosystems control on atmospheric CO2 interannual variability: Inferred from a significant positive correlation between year‐to‐year changes in land precipitation and atmospheric CO2 growth rate , 2000 .

[78]  Stefan Rahmstorf,et al.  The Thermohaline Ocean Circulation: A System with Dangerous Thresholds? , 2000 .

[79]  V. Fomichev,et al.  A model estimate of cooling in the mesosphere and lower thermosphere due to the CO2 Increase over the last 3–4 decades , 2000 .

[80]  M. Collins.  The El Niño–Southern Oscillation in the Second Hadley Centre Coupled Model and Its Response to Greenhouse Warming , 2000 .

[81]  W. Grabowski.  Cloud Microphysics and the Tropical Climate: Cloud-Resolving Model Perspective , 2000 .

[82]  E. Zorita,et al.  Disagreement between predictions of the future behavior of the Arctic oscillation as simulated in Two different climate models: Implications for global warming , 2000 .

[83]  John F. B. Mitchell,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 , 2000 .

[84]  R. Lindzen,et al.  An Energy Balance Model Based on Potential Vorticity Homogenization , 2000 .

[85]  T. Stocker,et al.  Abrupt climate change in the computer: is it real? , 2000, Proceedings of the National Academy of Sciences of the United States of America.

[86]  K. Kodera,et al.  Tropospheric and stratospheric aspects of the Arctic oscillation , 2000 .

[87]  U. Mikolajewicz,et al.  The role of the individual air-sea flux components in CO2-induced changes of the ocean's circulation and climate , 2000 .

[88]  Donald R. Johnson,et al.  Numerical Uncertainties in the Simulation of Reversible Isentropic Processes and Entropy Conservation , 2000 .

[89]  Adam A. Scaife,et al.  The GCM–Reality Intercomparison Project for SPARC (GRIPS): Scientific Issues and Initial Results , 2000 .

[90]  N. Gillett,et al.  Modelled and observed variability in atmospheric vertical temperature structure , 2000 .

[91]  S. Running,et al.  Contribution of increasing CO2 and climate to carbon storage by ecosystems in the United States. , 2000, Science.

[92]  H. Grassl,et al.  Status and improvements of coupled general circulation models , 2000, Science.

[93]  J. Marotzke,et al.  Abrupt climate change and thermohaline circulation: mechanisms and predictability. , 2000, Proceedings of the National Academy of Sciences of the United States of America.

[94]  Michael G. Ryan,et al.  Evidence that decomposition rates of organic carbon in mineral soil do not vary with temperature , 2000, Nature.

[95]  Ü. Rannik,et al.  Respiration as the main determinant of carbon balance in European forests , 2000, Nature.

[96]  J. Perlwitz,et al.  The leading variability mode of the coupled troposphere-stratosphere winter circulation in different climate regimes , 2000 .

[97]  M. Latif,et al.  Tropical stabilization of the thermohaline circulation in a greenhouse warming simulation , 2000 .

[98]  R. Betts.  Offset of the potential carbon sink from boreal forestation by decreases in surface albedo , 2000, Nature.

[99]  M. Holland,et al.  The impact of rising atmospheric CO2 on Simulated sea ice induced thermohaline circulation variability , 2000 .

[100]  T. Delworth,et al.  Implications of the Recent Trend in the Arctic/North Atlantic Oscillation for the North Atlantic Thermohaline Circulation , 2000 .

[101]  O. Boucher,et al.  Estimates of the direct and indirect radiative forcing due to tropospheric aerosols: A review , 2000 .

[102]  M. Schlesinger,et al.  Description and performance of the UIUC 24‐layer stratosphere/troposphere general circulation model , 2000 .

[103]  John A. Knaff,et al.  How Much Skill Was There in Forecasting the Very Strong 1997–98 El Niño? , 2000 .

[104]  R. Tolson,et al.  Evidence of long term global decline in the Earth's thermospheric densities apparently related to anthropogenic effects , 2000 .

[105]  R. Betts,et al.  Acceleration of global warming due to carbon-cycle feedbacks in a coupled climate model , 2000, Nature.

[106]  C. Covey,et al.  Vertical correlations of water vapor in GCMs , 2001 .

[107]  M. Jacobson.  Global direct radiative forcing due to multicomponent anthropogenic and natural aerosols , 2001 .

[108]  P. Dirmeyer.  Climate Drift in a Coupled Land–Atmosphere Model , 2001 .

[109]  K. Weickmann,et al.  Trend in Atmospheric Angular Momentum in a Transient Climate Change Simulation with Greenhouse Gas and Aerosol Forcing , 2001 .

[110]  W. Soon,et al.  Modeling climatic effects of anthropogenic carbon dioxide emissions: unknowns and uncertainties. Reply to Karoly et al. (2003) , 2002 .

[111]  B. Soden,et al.  WATER VAPOR FEEDBACK AND GLOBAL WARMING 1 , 2003 .

[112]  Comment on Soon et al. (2001) 'Modeling climatic effects of anthropogenic carbon dioxide emissions: unknowns and uncertainties' , 2003 .