I am a little confused as to what the "scientific fact" is here. The essence of the scientfic method is the ability to reproduce the event under dispute. We know the Law of Gravity is factual because we can drop an item and measure the rate of acceleration. We can duplicate that experiment endless times with the identical result.
With AGW, all I can discern is a "theory" or more likely, an "hypothesis." Scientists have proposed a link between man-made CO2 and climate change. Unfortunately, as pie observed, the complexity of the systems involved makes scientific proof difficult. Instead of reproducible experiments, we get models, but they are deeply flawed. Unbiased observers have to be concerned that the models have all vastly overpredicted the degree of warming. We are left to speculate if the scientists just do not understadn the processes involved sufficiently to model them accurately or if an agenda is at work. The hysterical tone of the debate and attempts to silence those who voice doubt suggest the latter.