Climate models (Encyclopedia of Environmental Issues, Revised Edition)
Climate models can be used to explore various scenarios; scientists use such models both to study the past (such as linking the ice ages to the rise of the Himalayas) and to project what may occur in the future. No matter how precise or accurately worked a model is, however, the information it provides is merely theoretical and must be verified against actual data, either experimental or (in the case of climate) observational. In addition, a model that accurately reflects the recent known past may have been written to do so.
The key models used in climate research are extremely complex general circulation models (GCMs). An ideal GCM would take into account every factor in climate, but in practice some factors are either ignored or simplified, even in the most complex models. Among these factors are volcanic eruptions, solar output, oscillating weather patterns (some taking a few years, others several decades), the water cycle (evaporation, condensation into low-level clouds, and precipitation all move heat from the surface to the troposphere), atmospheric content (including greenhouse gases such as water vapor and carbon dioxide, as well as pollutants such as sulfur dioxide), ocean currents, wind patterns, and land use (urban areas are much warmer than farmland, which is warmer than forest). None of these is entirely predictable, and some are random in occurrence. Local events can have major global effects; for example, El Niño conditions...
(The entire section is 586 words.)
Further Reading (Encyclopedia of Environmental Issues, Revised Edition)
Mann, Michael E., and Lee R. Kump. Dire Predictions: Understanding Global Warming. New York: DK, 2008.
Michaels, Patrick J., and Robert C. Balling, Jr. Climate of Extremes: Global Warming Science They Don’t Want You to Know. Washington, D.C.: Cato Institute, 2009.
Spencer, Roy W. Climate Confusion: How Global Warming Hysteria Leads to Bad Science, Pandering Politicians, and Misguided Policies That Hurt the Poor. New York: Encounter Books, 2008.
(The entire section is 67 words.)