BOX 10.1

In the fall of 1994, the interagency Subcommittee on Global Change Research arranged for the special Forum on Global Change Modeling to provide an indication of the state of current progress in improving understanding of global change and to provide direction for future research. This forum served as a means of bringing together a representative set of scientists to develop a consensus statement on the credibility of global model estimates of future climatic change. The charge to those attending the forum and to those who submitted written comments was to develop a brief statement on the credibility of projections of climate change provided by general circulation models (GCMs) as background for potential interpretation of model results in the context of developing and considering national policy options. The focus of the forum was specifically on the climate aspects of the entire global change issue—thus not on the emission scenarios, the consequences of change to ecosystems and natural resource systems, or the socioeconomic implications and potential for responses. Still the results of the forum are of significant value to this chapter.

The forum identified a number of areas where sustained or intensified research efforts would bring important gains in understanding and predictive capabilities. As an overarching statement it was noted that “while progress is clear as a result of ongoing research efforts and important steps can be taken over the coming decade that will bring new insights, significant reductions of the uncertainties in projecting changes and trends in the climate will require sustained efforts that are very likely to require a decade or more.”

“Progress will require significant effort because the problems are complex, because improvements in model parameterizations will require a sustained and long-term program of research and observations, and because the records of past changes and influences require careful reconstructions to make them more complete and more useful. Although progress may be modest, there are a number of processes and feedbacks on which research must be sustained because of the large leverage to be gained from improved understanding. These processes and feedbacks include:

  • cloud-radiation-water vapor interactions, including treatment of solar and infrared radiation in clear and cloudy skies (also including resolution of uncertainties concerning anomalous solar absorption);

  • ocean circulation and overturning;

  • aerosol forcing, requiring information on aerosol character and extent;

  • decadal to centennial variability;

  • land-surface processes, including the climate-induced changes in the structure and functioning of ecological systems with resultant changes in global chemical cycles;

  • short-term variability affecting the frequency and intensity of extreme and high impact events (e.g., monsoons, hurricanes, mesoscale storm systems, etc.);

  • non-linear and threshold effects that create the potential for surprises; and

  • interactions between chemistry and climate change and improved representation of atmospheric chemical interactions within climate models, thereby leading to improved understanding of the causes of trends in CH4, N2O, O3, CFCs, and aerosols.”2

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