How do global warming modles supposedly work?

 . . . . .    all [mathematical] models are first tested in a process called Hindcasting. The models used to predict future global warming can accurately map past climate changes. If they get the past right, there is no reason to think their predictions would be wrong.

Where models have been running for sufficient time, they have also been proved to make accurate predictions. For example, the eruption of Mt. Pinatubo allowed modellers to test the accuracy of models by feeding in the data about the eruption. The models successfully predicted the climatic response after the eruption. Models also correctly predicted other effects subsequently confirmed by observation, including greater warming in the Arctic and over land, greater warming at night, and stratospheric cooling.
(Source: Skeptical Science,  actually a pro-waming publication.)  

Notes:  This is an insult to the objective thinker.  In practical terms,  this is what is being posited in the above:  Speculative Science takes a historical event such as a volcanic eruption,  makes note of environmental influences that existed before the eruption,  assumes these influences to be causative as relates to that eruption,  and, then pronounce these influences to be predicted.  

What these genius's don't tell you is this:  If you work backwards from an event,  there is no possibility for a predictive analysis.  It is just plain stupid to suggest otherwise.  

Here is a fact:  Speculative Science cannot predict any single environment event that exists in the future.  None.  Take the Ozone Hole.  It was going to increase to the point that we were all going to sunburn to death.  Well,  today,  that hole is getting measurably small and smaller.  Remember Acid Rain.  The prediction included the end of plant life as we know it.  How about "tide rise."  Specifically,  the Twin Towers Memorial foundation would be under 20 foot of sea water by 2015.  How about the aftermath of Katrine (2005).  It was billed as the beginning of the end   -  as many a 17 major hurricanes the following year.  Turns out there was exactly "zero" storms.  And there have been no more than three major storms in the Gulf in the 12 years since Katrina.  

Again,  Speculative Science cannot predict when a dog will mess in your neighbors yard or when a swarm of bees will attack ex-President Obama or what the temperature will be in D.C.,  eight months from now on a Tuesday.