A Web-based system to access climate model output data sets for intercomparison and analysis has been produced, using the Live Access Server software developed by NOAA-PMEL as host server and Ferret as the data serving and visualization engine. Called ARCAS ("ACACIA Regional Climate-data Access System"), and publicly accessible at http://dataserver.ucar.edu/arcas, the site gives access to climate model outputs from runs of NCAR's Climate System Model and Parallel Climate Model spanning the 20th and 21st centuries, for Business as Usual and CO2 scenarios. Users can select, download, and graphically display single variables or comparisons of two variables from any of the model runs, averaged for monthly, seasonal, or annual time resolutions. The time length of the averaging period, and the geographical domain for download and display, are fully selectable by the user. A variety of arithmetic operations on the data variables can be computed "on-the-fly", as defined by the user. A new capability of the ARCAS system, currently under development, is animation, where, for example, a user may animate a sequence of monthly anomalies of temperature over the 21st century to examine the spatio-temporal evolution of global warming. The animation facility allows the user all of the options that apply to the other display options of ARCAS, including the ability to select specific regions of the globe.