Climate Models 
Science of Global Warming, Climate Change: Climate Models
CLIMATE MODELS are based on physics and run on supercomputers. They are indispensible for understanding climate, they have been tested, and they work. Go to:
Model INPUTS
Model TESTS from temperature data
Model FORECASTING and scenarios
Where can I GET MORE INFORMATION about models?
How about a VIDEO on modeling?
MODEL INPUTS INCLUDE ALL EFFECTS
These models use natural (e.g. solar) and anthropogenic inputs. Here is a graphic for the inputs to the climate models. Note that both natural (including solar) and anthropogenic effects are included.
Below is a graph of the time dependence of the various forcings relative to 1880, used as input to NASA/GISS models:
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MODEL TESTS FROM TEMPERATURE DATA
The temperature is an output of the models, and is not the result of a "fit" to parameters. As shown in the graphics below, the climate models have been successfully backtested against the last 100 years of temperature data (black lines) on a global level and at a continental level. The output of the models including all effects (anthropogenic/human and natural) are shown in red, which follow the data including recent global warming in the last 30 years. Natural effects only, in blue, are NOT sufficient to produce agreement with the data, especially in the last 30 years. Model uncertainties are exhibited by the bands. For all the supporting details, see the report.
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Below is the graphic for the model forecasts for the average global temperature over the next 100 years. Forecasts require scenarios. A scenario represents a set of assumptions of human behavior in the future. All the forecasts predict increasing global temperature trends, depending on the scenario: rapidly increasing temperatures if "business as usual" (A2 red), less rapidly increasing temperatures if action is taken against global warming (B1 blue, A1B green). For each scenario, there are uncertainties in model behaviors, shown in the vertical "error bars" (gray) on the right. The baseline (orange) is irrelevant since it assumes no increase in greenhouse gases.
Note that the graph is in Centigrade (one degree C = 1.8 degrees F).
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WHERE CAN I GET MORE INFORMATION ON MODELS?
A thorough description of climate models, with references, can be found in the 2007 IPCC Science Report. For specific global models see, e.g. the Princeton GFDL/NOAA site and the GISS/NASA site (with the computer code here). HERE is an article showing the steady improvement of climate models in comparison with climate data. Here is an interesting VIDEO of recent development of modeling using desk-sized supercomputers.
IPCC Science Report Download Here: Climate Change 2007 - The Physical Science Basis: Working Group I Contribution to the Fourth Assessment Report of the IPCC.
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HERE is a great VIDEO describing the history of climate modeling:
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