Clima-Sim is a small climate simulator model that can be run on a PC.
Spurred in part by a curious WxSim customer (Ton Lindemann) two decades ago, Tom Ehrensperger (WxSim author) embarked on an off-and-on quest to create a small climate model that could be run on a personal computer. Many aspects of climate modeling, such as cloud physics, were well beyond his expertise. However, the energy balance aspect of climate modeling was very much down the same alley as the work he’d done for WxSim. He decided to make a 1296 cell (36 x 36, every 10 degrees of longitude and a variable scale of latitude, to equalize cell areas) ‘map of the world’, with solar energy in and out, and heat exchange (via advection, primarily) between adjacent cells. He made the surface type user-modifiable, as well as a host of other things, like solar luminosity, axial tilt, orbital eccentricity, and whether or not to include various feedback effects and circulation patterns like ocean gyres and trade winds.
He worked for many years on this model, tweaking, tuning, and adding features. He calibrated it in a number of ways, but largely by getting its output to match paleoclimactic extremes, such as the Last Glacial Maximum about 20,000 years ago, and the very warm Cretaceous, about 90 million years ago, using all the data he could find regarding global and zonal temperatures, atmospheric composition, solar luminosity, and continental configurations. However, the default values of the various parameters he tuned are still tunable in the program, so that you can do a “world” of experiments and simulations yourself!