In 1991 I published a paper which had my views on the issue of the GCM modeling of global warming. This weblog revisits the topics I raised at that time.
Pielke, R.A., 1991: Overlooked scientific issues in assessing hypothesized greenhouse gas warming. Environ. Software, 6, 100-107.
I summarized the focus of my article in the text
“Numerical models of the global atmosphere and ocean circulations (referred to as general circulation models -GCMs) have been used to investigate the impact on climate of an increase in these trace gases [which include carbon dioxide, methane, chlorofluorocarbons, and nitrous oxide]. The Environmental Protection Agency (EPA) concluded in 1983 based on these models, for example, that an increase of the average global temperatures of 5°C by the year 2100 with an incrcase or sea level up to around 2 meters will result because of the global enhancement of these gases. The World Meteorological Organization has concluded that greenhouse gas cause warming could cause a global warming of 1.5°C to 4°C by the middle of the next century.
The purpose of this paper is to discuss a number of serious shortcomings in the GCM model simulations which produced these conclusions regarding climate change, These limitations, which are either inadeqately handled or not represented at all in GCMs are summarized in this paper.”
The following are the issues that I have raised, and what has been accomplished since the appearance of this paper:
1. INCREASED CARBON DIOXlDE CONSUMPTION RESULTING FROM INVIGORATED PLANT GROWTH ON LAND AND IN THE OCEAN
Biogeochemisty and biogeography are now recognized as first order climate effects [e.g see NRC, 2005].
2. INABILITY FOR GCM MODELS TO PROPERLY RESOLVE THE EVOLUTION OF EXTRATROPICAL AND TROPICAL CYCLONES DUE TO THER POOR SPATIAL RESOLUTION
Even though the models now have finer spatial resolution, The IPCC community still fails to recognize that they must test the ability to faithfully simulate weather features (i.e. they need to be run in a numerical weather prediction mode). This is a necessary test in order to evalute the dynamics and thermodynamics in the GCMs.
3. INABILITY FOR GCM MODELS TO PROPERLY RESOLVE REGIONS OF OCEAN UPWELLING WHOSE COLD WATERS CAN ENHANCE THE OCEANIC UPTAKE OF CARBON DIOXIDE
The issue still requires futher investiagation. I would welcome urls of peer reviewed papers that have looked at this specific issue [which is directly related to the spatial resolution in the ocean part of the global climate models, as well as both the physical temperature effect and the biogeochemical (carbon assimilation) effect on ocean biomass].
4. OCURRENCE OF GREATER GLOBAL CLOUD COVERAGE AS A RESULT OF COLLODIALLY MORE STABLE CLOUDS DUE TO ANTHROPOGENIC INPUT OF AEROSOLS
This climate forcing is now recognized as a major effect on the climate system [NRC, 2005]. Its complexity, however, and the microphysics spatial scales in which this occurs, continue to challenge skillful modeling of this process.
5. MODIFICATION OF THE AMOUNT OF SOLAR RADIATION REFLECTED BACK INTO SPACE DUE TO MAN-CAUSED LANDSCAPE CHANGE
This effect is included in the 2007 IPCC report.
6. MODIFICATION IN THE AMOUNT OF EVAPORATION AND TRANSIPIRATION TO THE ATMOSPHERE AS A RESULT OF MAN CAUSED LANDCAPE CHANGES
This has been one of my major research areas, and it has been elevated to a first order climate effect (e. g. see NRC, 2005), although the 2007 IPCC failed to adequately discuss it.
7. CLOUDS WHICH CONTAIN SULPHATE PARTICLES, RESULTING FROM FOSSIL FUEL COMBUSTION, HAVE HIGHER ALBEDO THAN PRISTINE CLOUDS
As with #4, this climate forcing is now recognized as a major effect on the climate system [e.g, see NRC, 2005]. Clouds and precipitation process are not seen, however, as an even more difficult modeling issue than in the early 1990s (e. g. see Table 2-2 in NRC, 2005).
8. GREATEST WARMING IS PREDICTED TO BE IN POLAR REGIONS, AND YET WARMING HAS NOT OCCURRED.
This warming has occured in the Arctic (and, while there is disagreement), it has not warmed in the Antarctic region at the same level.
9. SINCE THE ATMOSPHERE IS A NONLINEARLY RSPONDING SYSTEM. EVEN WITH ALL RELEVANT PHYSICS FAITHFULLY REPRESENTED. THE GCMS COULD ONLY SIMULATE EXAMPLES OUT OF A SPECTRUM OF POSSIBLE ATMOSPHERIC RESPONSES TO INCREASED GREENHOUSE GASES
The 2007 IPCC continued to perpetuate the view that the models can skillfully predict the climate in the coming decades despite their own admission that the GCMs do not even have all of the first order climate forcings (see the caption to figure SPM.2).
I summarized my recommendations are follows
“Since climate change is a natural feature of the earth, we need to husband our resources even if there were no man-caused changes (e.g. Schneider). With respect to man’s potential influence on climate, the “path-of least- regret” is that we should immediately adopt policies which mitigate man’s impact providing there are no deleterious economic, environmental, or political effects of these policies. Even better, of course, is if these policies result in positive benefits to mankind. Conservation of fossil fuel resources, for example, and utilization of renewable energy resources represent examples of beneficial activities which should be promoted by government policy makers regardless of the direction of climate change. Recommendations by Rosenfeld and lIafemeister represent definite steps which could be taken to achieve this goal. Policies which require significant hardship, are in this writer’s opinion premature.”